Munk's Motors - Master Cylinder Tech Tips!

Q - I have a 1987 Cabriolet. I put the top down, left it parked, and a cloud burst flooded the car! What should I do? Is it OK to just start it up?

A - First, smack yourself in the forehead and resolve to never do it again. Next, disconnect the battery, remove the driver seat, remove the DME computer and carefully remove the circuit board inside. Check for moisture and corrosion. After letting it dry, put it all together reconnect the battery, and pray.
MC

Q - When if first start my 1990 Carrera 4 I hear a funny noise like a high speed zipper back in the engine compartment. By the time I open it up to look, the noise goes away. When the car is warm, I never hear the noise.

A - On Carreras with two belts, one for the fan and another for the alternator, Porsche needed a warning light to alert you if the fan belt broke. That noise you hear is the tiny little idler wheel that is keeping tabs on the fan belt. It's a little roller attached to a bracket with an arm on it. Temporarily, you can put a little spot of oil on the bearing to make the annoying sound go away but you better order another of those sensors. I have seen the little device without the idler even on, ty-wrapped in place so the light would NEVER go on. This is a recipe for disaster since you could burn up your engine without even knowing.
MC

Q - I notice that when I try to raise the top on my Cabriolet, it tends to "stick" on one side and the motor makes a groaning sound unless I lift it up a little. How come?

A - There are a few reasons for this. On the Cabs, the top tends to loosen up as a normal process of wear and tear. In a nutshell, the screws that hold it together, the locating pins, and the bolts that secure the gearboxes to the car simply vibrate loose. The gearboxes are only held in by three long 6mm bolts! (that is pretty small considering the load) There was also a technical service bulletin that applies to mid 95 and earlier cars which suggests replacing the top pins with Targa locating pins which are shorter. The part number for the shorter pins is 911 565 074 40 and they are only about $15.00 per pin
If you hear that groaning sound or if the top bangs hard as it is coming down, you could facing a major expense if you ignore it. Then best case scenario is that tightening and adjusting the top will restore perfect function. In the worst case, you can break the top parts or even rip the top…at huge expense. With the top part way up (or down), try rocking it back and forth and see what is loose. You might be surprised. And if it sticks or binds avoid using it until you get it fixed.
Recently I inspected four Cabriolet top mechanisms and ALL FOUR had loose parts. One of them came in with the top literally ripped off when it opened (by itself) on the freeway. It pays to have good insurance and a well adjusted top.
MC

Q - When I hit the brakes on my 1991 Carrera, I feel a shaking in the steering wheel. The wheel kind of twitters back and forth. I had the brake pads and rotors replaced two years ago because I was getting the same symptom and after that, it went away. Now that bad old feeling has returned even though I was told that my brakes looked fine last time the car was inspected. This is very frustrating.

A - Frustrating is only the half of it, expensive is the other half. When your brakes were done last, the original cause of the symptom wasn't figured out and that's why they are doing it again. Porsche has an elegant way of engineering their parts and on your car, the pads slide on stainless steel spring plates that are screwed into the calipers. Corrosion sets in under those plates causing the pads to "stick". The brakes functioned safely, but the pads simply did not fully release. The excess heat build up in turn warps the rotors.
Removing those plates it important to get a long lasting job but it is not easy. Those little screws usually do not come out without a fight and if you are in a hurry, they can break right off.
The other issue with brake shake that you can feel in the steering wheel has to do with all the wear and tear on your steering system. If you ignore the shake, the tie rod ends, inner sockets, steering rack, ball joints, and steering shaft all have to soak up that annoying vibe before it even reaches your nervous palms. Now that can make it a lot worse.
MC

Q - I had the brakes replaced on my 993 at an independent shop and now six months later, there is rust on the inside of the brake rotors when you look through the spokes of the wheels. Did they put cheap parts on my car? Why are they rusty? The original rotors never were.

A It is unlikely that the rotors were cheap but that rust issue is annoying and it makes the job look cheap. Fact is, Porsche uses a protective gray coating on their rotor "hats" and only their rotors come with that coating. That does not make them work better, it just keeps corrosion from forming on the exposed (non working) surfaces. When I install rotors, I use a Zinc Cold Galvanized coating on the rotor hats. On my own car, I even sprayed it into the cooling vanes and the drilled holes (yeah, I am a bit picky). That rust does not hurt anything, it just looks tacky.
MC

Q - I have a 1987 Carrera and when I turn on the heater, I hear a squealing sound coming from the heater fans. After it is on for a while, the noise goes away but I am afraid that something is not right.

A - Trust your intuition. The bearings in those fans are knows for drying out and if you run it that way, you will burn them out. My car does this too and I will get back to you with a solution (short of outright fan replacement) after I experiment with my own car (and my own time)
MC

Q - I have a 993with a full shield under the engine. My tech said to remove it with the benefit being a cooler running engine. Since Porsche put it their, I am not sure if I should take his advice or not. What is it there for if it is not important?

A - Darn good question Cliff. I thought that it was an aerodynamic aid that helped streamline the car and I further thought that, where in America can you drive fast enough to reap the benefit of it. Now I know that we can blame it on the Swiss. Noise regulations in Switzerland are so strict that this under tray is there to keep sound at bay. If you leave it on, your Porsche will not only be quieter, it will also run a little hotter! Who needs it? My suggestion: Take it off and hang it in your garage for posterity and for the next owner of your car.
MC

Q - On my 1996 993, I just paid a lot of money to have the oil changed. What makes it so hard to change oil on these cars?

A - 1) They hold a lot of oil, 2) The more oil they hold, the longer it takes to drain and fill, and 3) To drain the oil and change the filters, you have to remove panels that are in the way.
It was suggested to me that certified technicians did not have to add the oil, that apprentices could do it and do it cheaper too. I am not sure I like that idea on my Porsche but as a cost saving measure, you could offer to add the oil next time you have it changed. That usually takes about 20 minutes and at Porsche labor rates, it might save you over 20 bucks. The other cost saving idea would be to see if the facility offers you a "quantity discount" since they are selling you almost two cases of that expensive synthetic oil. I am not saying that you will get any takers, but you can always ask. As far as doing the oil change yourself, that is always an option but a messy one.
MC

Q - When I first started my 911 up in the morning, the oil level gauge was all the way into the red. It really worried me so I added oil until it was full. Now my car smokes like crazy and oil is dripping from the right rear fender. Did I ruin my car?

A - Chuck, my student, you have committed the first travesty of the 911 world by believing your oil level gauge in the morning. Your car holds 11 quarts wet and about 13 quarts dry! Don't feel bad about it though, I have done the very same thing. Maybe you have to do it once to become initiated into the Porsche fraternity.
In the morning, you may be able to find oil at the bottom of the dipstick but never fill it up until you have met the criteria in the owners manual regarding temperature. I know, it is not mainly to read the manual but in this instance, you must. As far as the mess, your right frame rail will never rust since it is now internally coated with oil. Drain a couple quarts and check it again when it is hot.
As far as ruining your car, that is unlikely but it may take a while for the smoke to go away. Anyone you know planning a picnic? Got a mosquito problem?
MC

Q - I have a 1968 911. When I took the car in to have the chain tensioners replaced with the pressure fed, upgraded variety, none of the parts fit! It apparently has a 1967 engine in it even though the numbers match. How can this be? Is there a way to retrofit the later tensioners to my engine?

A - No problem, John. Porsche was not too strict regarding the exact engine they installed in a certain year car. Sometimes they used up the engines they had left over from the prior year. In addition, cars built the year before are often titled as the year they are sold. What you have is a 1968 with a 1967 engine in it. That is where it gets interesting.

The tricky part is retrofitting the later tensioners. It can be done but it requires block modifications to do it since the studs do not line up. Then you would also have to buy new chain boxes. Unless you are planning to overhaul the motor, it would be cost prohibitive. Considering how many miles you intend to drive the car, I suggest using the original style but updated design tensioners along with the "stops" to keep them from fully collapsing. In addition, the pivots should be replaced with the updated design at the same time. The original design should work fine for about 40,000 miles between rebuilds, perhaps more with modern oil technology.
MC

Q - My 99 Carrera four eats tires!! I have only been able to drive about 10 to 15 thousand miles before the inside of the rear tires are bald. I didn't even notice it since the outside tread, the part I could see, looked fine. The last time I had the car serviced, the tech advised me that with Porsche alignment specs, that was normal. Normal for who, I am not Donald Trump! I do not track the car and only occasionally drive it hard. What do you suggest? (I know I shouldn't complain, it is a Porsche after all and I can afford it, but damn! Those tires cost about $400 bucks each!) Help!

A - "Your Porsche is a finely tuned machine" and yes it DOES eat tires. It also handles like an overgrown go kart and yes, of course, you can afford it, you lucky dog. The question is one of compromise. Many folks that I advise want decent tire wear and are willing to sacrifice ultimate handling to get it. The local Porsche dealer and the tire store may not like it, but with a less aggressive rear toe setting, your car will no longer chew on that expensive rubber and it will still out-grip, and out-handle, 99.8 percent of the other cars on the road.
Will it affect handling adversely? No, not unless you are driving your car at it's limits. Will the purists lament? Don't tell them…but when they complain about how many rear tires they have gone through, just smugly say, "Yes, I had that problem once", and leave it at that.
MC

Q - I have a 96 Targa and my check engine light keeps coming on. It has been shut off numerous times but in a few weeks, it comes back on. The diagnostic codes that set don't make sense to me but my mechanic says that the secondary air system has failed. He wanted 4 grand to pull the motor and correct the problem. To me this is absurd and besides, the car runs great. Can I get a reality check on this?

A - Be aware that the check engine light can set for numerous reasons and that computer is still not smart enough to diagnose the problem. It only gives you clues. I know a number of clients who have fired the “parts cannon” at their cars only to discover that the computer lied.

Your mechanic is correct on one point. Odds are, the secondary air system is the source of the problem but pulling the engine to fix it IS absurd. The likely culprits are clogged holes in the cylinder head exhaust ports near the exhaust valves.

Fortunately, the holes can be accessed from under the car by removing the exhaust and heater boxes. On an older car, this might be easier said than done. The nuts securing the exhaust are usually rusty so finesse is required to remove the exhaust. If you do not have a source of heat to warm them up, don't try it, the penalty for breaking a stud is pretty stiff. We have had more than one car towed in after the owner tried to do it himself.

Once the system is off, you probably will not be able to see the holes since they are packed with carbon deposits and somewhat hidden behind the valves. I fabricated a “port cleaning reamer” out of an old accelerator cable chucked into my trusty Makita cordless drill.

Once you clean the deposits off the exhaust port surface with carburetor cleaner, you can find the holes and start feeding the cable into the holes to break through the clogs. Work at it gradually and let the carburetor cleaner do the work for you since you do not want to push the carbon up into the ports.

Once you get the ports nice and clean, reinstall the exhaust and you are on your way. The total cost; about $800.00 dollars or so, plus gaskets and hardware. This is not a guaranteed fix, but for the money it is a good option and every car I have inspected for this has had clogged secondary air holes.

By the way, while the exhaust is off, you can clean all that stainless steel with Scrubbing Bubbles and Scotchbrite (if you are as anal as I am). This is a great way to clean around the exhaust cutouts on the rear valance and to get the tail pipes back to new as well.

MC

Q - I have a 1984 Targa and my windows go up too high. It makes it hard to shut the door unless I lower the window a little. The window hits side of the weather-stripping and then the window sticks out. It also leaks! I removed the door panel and I could see a stop for the window with a chunk of plastic. It looks bent. What do you suggest?

A - Porsche offers a repair part for the window regulator that can be installed once the regulator is removed. It is stronger than the original and will probably last another twenty years or so. The other option is a new, improved window regulator. It is a more robust design and a permanent cure but it requires slight modifications to fit. The part costs about two hundred dollars but if you enjoy tinkering, for about 20 bucks, you can save the extra cash and take your wife out for a really nice dinner in your Porsche.

MC

Q - I have a 1985 Carrera and since it is my first Porsche, I probably got in a little over my head but here goes. It has an oil leak at the pipe connecting the engine to the oil thermostat (it's the one with two solid steel ends and some braided hose in the middle). I was thinking of changing it myself but I discovered that it takes special tools to get it off the thermostat and what's worse, the hose costs $284.00! Help, I didn't realize that this car would be so expensive.

A - First, Chuck, I share your pain. These cars can suck your wallet dry faster than a 6 hp. shop vac. But I have found a simple and cheesy solution to your dilemma. You can rest assured; it is not endorsed by Porsche nor is it a guaranteed fix. The flexible part of the hose is probably leaking and it is secured by crimped-on clamps called ferrules. When the hose is new, these make a fine seal but when the hose ages and shrinks, the fit loosens and the leak begins. If the ends of the hose are leaking, replacing the ferrules with clamps might help. Incidentally, on the race engines built by Jerry Woods, he also feels that clamps are more reliable and he ought to know.

To remove the ferrules, you need to cut them through and break them off the hose. The easiest method for this is a cutting disc on a high speed die grinder. You will have to make three or four cuts to weaken them sufficiently but do not cut into braiding of the hose or the game is over.

Once they are cut, squash them with Channel Lock pliers and remove the chunks. Replace the ferrules with two hose clamps per end. Clean up the mess with Gunk Engine Brite and a power wash to see if the cure worked. If that is where the leak was happening, you have solved it for 10 dollars and about two hours of your time.

MC

Q - On my 1992 Carrera, the sun visors are very stiff. I am afraid they are going to break unless I use both hands. How do you oil them? - Greg

A - If you have to use both hands, you will definitely going to break them and it's not wise to oil them. Porsche provided an adjustment screw near the pivot to regulate the amount of friction (tightness) in the hinge. If you have too much friction, a simple adjustment or service will fix it.

To adjust the friction, simply loosen the screw a little and see how it works. If you are not happy with the way it feels, the moving parts are not hard to service. To make them move nice and smooth, remove the visor assembly and loosen the adjustment screw (don't remove it). Rotate the “stem” of the visor bracket while pulling it out of the visor. Clean the stem, spray some silicone into the hole, and reinstall the stem into the visor. Install the assembly then tighten the adjustment screw until it operates smoothly.

MC

Q - After 89k miles, my 1991 Carrera is feeling a bit arthritic and loose over bumps. I am considering Bilstein coilover struts. I also want to lower it about an inch and a half but I am afraid that the ride might be rough. What do you think? - Fred

A - I like that combo. Even without adjustable damping, the Bilsteins work great. They are biased more toward crispness than comfort but on a Porsche…Perfect. On the other hand, if you simply install the kit without considering other components, you might be disappointed and blame it on the shocks. Often, poor ride characteristics are caused by the rear upper strut mounts, front control arm bushings, and stabilizer bushings.

You can't see the rear upper mounts when they are on the car. But when you do a side by side comparison of old mounts to new, you will see the difference. Since most of the cars weight rests on just two rubber donuts, after 17 years, the mounts are well done. Over time, rubber hardens and settles into a fully compressed shape. The front mounts on these cars seem more durable and they are expensive. I have not seen the need to recommend them even on higher mileage cars. Rubber deterioration also affects the front control arm bushings and stabilizer bushings. The bushings get twisted every time you hit a bump or bend your toy around a corner. And you thought you just needed shocks.

My rule of thumb for rubber suspension parts is: With a useful life of 10 to 20 years, when the struts and shocks are being replaced, replace the mounts and take advantage of the labor overlap.
MC

Q - I have a strange problem with my 1986 Carrera. After I turn a corner, I notice that my brake pedal drops very low. This is very disconcerting. As soon as I straighten the wheel and apply the brakes, the pedal feels normal again. I have flushed the brake fluid and taken it all apart twice! I rechecked everything I replaced: the front wheel bearings, rotors, and brake pads. I am tearing my hair out. - Heavy

A - Strange is an excellent word for this. My guess is that turning and loading the front wheel bearings pushes the brake pads away from the rotor. I have run into this and been annoyed by it myself. You can actually install incorrect wheel bearings if you don't compare them. Bearing sets can have the correct outside diameter but a larger inside diameter. Even though bearing preload is correctly adjusted, the bearing can “act” loose when turning. Cornering forces generate strong side loads. This allows the inner bearings to “walk” out of place, and rotor deflection pushes the brake pads away from the rotor. During straight line driving and braking, the wheel hub will stay centered since there are no “side loads” (and the brake pads stay close to the rotors”). Crazy.

A 1967 Beetle schooled me on this topic. The lesson: compare parts. A late night Detroit DJ used to sign off at night with: “Remember, trust everyone…but always cut the cards”. I considered my experience just another tuition payment. Good luck
MC

Q - I have been considering a muffler bypass on my 1997 Carrera. I think it might be too loud. Have you heard one? What about an aftermarket exhaust? - Chuck

A - I really like the way those cars sound without a muffler. In the best of all worlds, you could have a switch that would allow you to select “muffler” when you pass the cops or cruise steady and then select “bypass” when you want your Porsche to sound like one. If I had to live with only the bypass pipe, I might drive my car less and I couldn't hear my stereo on the highway, but oh, what a glorious sound. For most folks, it might be a little too loud.

I would recommend a abspeed exhaust based on the cars I have heard and driven. They fit well, do not drone excessively, and sound mellow. The best way to decide what you want is to attend an event, listen to everyone leave, then find out which brand he/she chose.
MC

Q - Help! My 96 Turbo is making me crazy. I love the car but I can't stand it any more. It smokes so badly that I could fog for mosquitoes and charge for it. The final straw was when I started it last week and my neighbor came over and asked if he should call the fire department. I am serious! I even made a video of it. And to make matters worse, now it acts like I am losing power and I feel a hesitation.

It only has 20K on the odometer. I have religiously followed the dealer's recommendation about oil and filters and it has never been anywhere BUT the dealer. Last visit, my service advisor said that the smoke was normal and that I should change to a heavier grade of oil. What could have gone wrong with it?br> Dave

A - Dave, I emphasize with you. I had to quit driving my turbo when it had the same problem. I couldn't take it to parties any more, it was embarrassing! Fortunately your turbo can't have the same problem as mine. From repeated flogging, I roasted the oil seals in mine. At 20k, I am certain that is NOT your problem.

It is an easily corrected design flaw. When Porsche redesigned the turbo for the early 90's, they mounted two turbos, down low in the chassis for faster acceleration and packaging. They also provided an oil reservoir for fresh oil at each turbo. The problem is, when you turn the engine off, residual oil, under pressure…fills the turbos and causes the smoke on start up. I would bet that this IS your problem.

The cure consists of two new oil lines with check valves to shut off oil flow after the engine is shut down. Unfortunately, many of these cars were diagnosed with “bad turbos” which of course did not cure the problem. For a time, while the cars were under warranty, Porsche would fix them free with updated lines. Although it is expensive, once you have the kit installed and clean up the mess, there is no permanent damage. It is a lot less expensive than replacing the turbos.

Even so, for a while the car will still smoke. I prescribe a fast drive on an unobstructed stretch of road to literally “blow out the pipes” This will clean some of the oil residue out of the turbos, pipes, intercooler and the intake. The oxygen sensors (a vital fuel trim component) are certainly coated with oil residue and it takes heat and time before the car will regain full power.

As far as the advice you received, service campaigns, updates, and recalls are the tools that an advisor should utilize when giving advice. You would be doing him a service to let him know about the cure if he ever runs into this again. As many professionals will tell you, free advice is usually worth what you pay for it and he simply did not do the research.

And although this might cure the smoking problem, what about your mental health? The answer for you may be “auto therapy”. Auto therapy requires discipline and repeated test drives. After a dozen or so smokeless start ups, you should start feeling better. Meditation in your car will also help with your therapy. My personal motorhead mantra is “c….h….r….o….m….e”. Take a deep breath and try to say it very slowly so the sound creates a resonance in your head. I also recommend auto yoga which involves various postures and movements which will improve concentration and promote a feeling of deep peace and contentment. Some hacks have called this “detailing” but they miss the point. It works for me. Try it.

As far as the neighbor, next time you see him, ask that smart aleck if he would care for a ride. Then slip it into first, smoke all four tires, snatch a few gears, and then tell him to hold on while you do a “brake test”. It may not change his mind, but for a few seconds, he will be speechless. And Porsche glory is restored.
MC

Q - I just bought a 2007 Carrera 4 and I plan to take it to Drivers Ed this year. I wondered what I could do to get more power. Is it possible to install a turbo or a supercharger? - Jim

A - The quick answer is: sell it and buy a turbo. But I understand, this is the car you have and you want to have as much fun as you can. I feel the same way about my car, and I want more power too. For more power, very little is available that does not involve a huge outlay of cash. For my money, I would start with a sport exhaust, computer reflash, and a cold air intake. You can expect modest gains in power but more importantly, your car will feel faster.

For the turbo or supercharger option, there are companies that develop kits for newer cars but it is getting difficult to improve on Porsche engineering. Another factor on a new car is warranty. Porsche backs their products with an excellent warranty as long as the car is maintained and operated in accordance with their standards. If you modify a car under warranty, they can always tell you to “take a long walk on a short pier” if something breaks.

For Drivers Ed, find out how much fun your car can be with only a few only minor mods and next fall, after a season of fun, pose that question again. Some summertime seat time may change your perspective. - MC

Q - I have been considering a muffler bypass on my 1997 Carrera but wondered if it would be too loud. Have you heard one?
Chuck

A - I really love the way Porsche's sound without a muffler. I wish there was a switch that would allow you to select “muffler” when you need to be discrete and “bypass” when you want your Porsche to sound like one. Until then, if I had to live with the bypass pipe, I might drive my car less and I would be nervous about getting caught. Consider one of the sport mufflers instead. Most of them fit well and sound mellow compared to the muffler bypass.

Next time you are at an event, listen to some of the cars that have a sport exhaust or muffler bypass. Ask if you can go for a ride in the car to see how it sounds. If you hear an exhaust that you particularly dislike, politely inquire as to the brand and eliminate that one from your list.

The price of experimentation is not too great when you consider the residual value of your first choice. If you buy something that doesn't suit you, you can sell it in the newsletter. Many gently used parts are purchased at fair prices. Don't be afraid of making a bad choice. It's your car and your privilege to change your mind.
MC

Q - My Carrera 2 stalls right after I start it in the morning. It always starts right back up but it never used to do this. It was an occasional problem but now it happens every time in the morning.

A - Fred Good news on two counts: 1) it happens all the time (intermittent problems drive me nuts) and 2) the cure is relatively easy.

When you turn your car off, the fuel system retains pressure in the lines just like your water faucet at home. Coincidently, the retained pressure for a home water system and fuel injection system are about the same, roughly 40 PSI. If the pressure leaks down, you would never know it since it leaks back into the fuel tank. This is a very common problem with many fuel injected cars as they age.

The cure involves first verifying the problem. In this case, a fuel pressure test will tell the story. When the engine is running, the pressure should measure a certain PSI and when you shut the car off, it will drop (but not to zero). If the fuel pressure drops too low, when you turn the key, it will take a few seconds until pressure builds. If the fuel pump check valve is the source of the pressure drop, the part is inexpensive and the labor is not bad either. Once pressure is retained, the car will start and run just as you remember it.
MC

Q - When I start my 1990 Carrera up in the morning, it clatters like someone has poured marbles in a blender. It scares the heck out of me but the noise goes away after just a few seconds. It only happens when the car has been sitting for a long time. I am afraid that I will damage the engine. How serious is this?

A - Mike That is an obnoxious noise isn't it? And yes, you should be scared. Noises like that usually get worse not better if you ignore them.

The first thing is to catch that symptom “in the act”. Since it only happens for a few seconds, an overnight stay will be needed and it will take two people to find it, one with a stethoscope at the ready and the other turning the key. Listen to the left side of the engine, just behind the distributor.

Odds are that you have a leaking camshaft chain tensioner on the left chain box. There are two tensioners, right and left and thankfully, the left one can actually be seen and touched (unlike a lot of things on your car). And the left one is the only one that I have found to fail.

The tensioners are supplied with oil pressure when the engine is running. When you turn the car off, they are supposed to stay filled with oil. But the tensioner on the left bank is mounted upside down and sometimes the oil leaks down. When you first fire the engine up, it takes just those few precious (and disconcerting) seconds for the tensioner to “pump up”.

The part is reasonably priced and the labor isn't bad either. It is a small price to pay to save your engine and your nerves.
MC

Q - I recently had occasion to replace the starter on my Carrera 4 and while I was under there (OK, I admit, I wasn't under there but my technician showed me) I noticed the red heater hoses were shredding. When I found out how much they cost, I about passed out. Is there an alternative other than contributing to the Porsche family trust?

A - Tim, I am well acquainted with another Tim who supplies Porsche parts at the local Porsche establishment and he agrees that those hoses are ridiculously priced. Although he cannot endorse Home Depot for Porsche parts, I can. And for this particular part, a 4 inch aluminum flexible dryer vent hose fits perfectly. Since no one can see the hose anyway, it will be our little secret. And you will save over a hundred bucks.
MC

Q - I just bought a track car, a one owner 88 Carrera and I am looking forward to this year's DE without sweating the damage I could do to my GT3. So I have a number of questions.

The former owner installed headers and has the oxygen sensor still installed in the left header but it is unplugged. Should I leave it unplugged or should it be connected.
The sway bar mounts in the rear are showing signs of cracking and I was told that a revised bracket is available. What should I do about it?
The AC does not work and I need to replace an oil line underneath the compressor anyway. Can I just remove the compressor and leave it off?

Wow Mike, this is what I call “living large”. While you are at the track with the Carrera, I would gladly exercise the GT3 for you. You really should not let these cars sit around.

But seriously, on item 1, the OXS sensor is an electronic “nose” that constantly monitors the fuel mixture and adjusts it based on “smell”. Do you notice that funny odor that you detect after a hard run at full throttle? That is raw un-burnt fuel. And although $4.00 a gallon gas is a factor, there are other considerations.

With the sensor wired into the fuel injection system, the amount of fuel compared to oxygen is constantly adjusted by the Motronic computer for peak engine efficiency except at full throttle. At full throttle, the computer ignores the sensor signal and uses a different “computer map” to give you maximum power. Or you might say “engineered maximum power”. This is where chips come in. A chip will give you more power by re-engineering the map to provide more advanced spark and a richer fuel mix. Simply unplugging the sensor causes the fuel mix to go “full rich” without the benefit of advanced spark timing. So the engine runs great at full throttle and ironically, it would do that anyway if the sensor were plugged in.

The other considerations have to do with increased engine wear by dumping all that extra gas into the engine when it does not need it and the comment by your better half: “why does your car stink?” My dear old Dad also claimed up to 10% better fuel economy in both of his chipped Porsche's (when he drove for economy).

My advice: Chip it, adjust the fuel mixture to base settings, plug the sensor back in, have it tested, and enjoy the best engineering that Bosch and Porsche built into the car.

On question two, the sway bar mounting brackets were poorly engineered from the start. By my rough guess, they are broken or cracked on better than half the cars I inspect. There are three methods of dealing with this:

If the bracket is completely broken, Porsche offers an updated stronger design that is priced at under $100.00 each (plus labor)
If the bracket is cracked, it can be reinforced before it breaks and this is equal to the updated bracket at a much lower labor cost.
There are aftermarket brackets that attach to that large round tube called the torsion bar housing. Although I consider these ugly, they work and they are cheap.

On question 3: Should you delete the AC compressor? On this model there is no down side to removing the compressor. There is only one wire to disconnect, the compressor is heavy and who needs it at the track? Before you remove it however, make sure any remaining coolant (Freon) is recycled. I suggest that you cap the AC hoses if you ever want to reinstall it. If you want to take this project a step further, that AC condenser under your turbo tail is not improving air flow to the engine either.
MC

Q - The AC blower motor on my 1980 Carrera has been working very erratic lately. It will work one time when I drive but when I stop the car to go shopping for a while, I come back and it won't work. If I let it sit for a few days it will work then and then not work. It even went out for a few minutes then came back on while driving. What is your opinion on the problem??? Motor going??? Control Switch?? Ground??? So just where is the motor located??? I assume it is in (what is commonly called) the smugglers box. I have a part # of 901 624 901 00 for the motor. Is this correct??? What is the cost of new motor???

A - Intermittent problems are the most challenging and all too often, do-it-yourselfers fire the “parts cannon” in desperation. Don't do that yet. There are some things you can check and even if they do not cure the problem, consider routine maintenance instead.

First check the fuses, but not to see if one is blown, that would be far too easy and the blower wouldn't work at all. With a strong light, notice the appearance of discoloration on the fuses and the wiring at the fuse block. Notice the different color of the fuses (which corresponds to their load value) and make yourself a diagram with those colors noted. If you find that some of the fuses have shrunk, you have fallen victim to plastic, third world fuses. The original fuses were ceramic and they do no melt or shrink. F.Y.I. Yellow is 5 amp, white is 8 amp, red is 16 amp, and blue is 25 amp.

Next, disconnect the negative battery cable and inspect the fuse box for integrity of the plastic base and then check all the screws securing the wires to the fuse holders. To check the screws, hold the base of the wire holder with needle nose pliers as you try to loosen then retighten the screws. If power flows through an overheated circuit, the screw might seem tight but be partly seized in place due to the heat generated. Typically, I find some screws loose, most of them tight and occasionally, a heat damaged terminal or fuse box. On many older cars, an auxiliary fuse box contains the AC fuses and I have found these broken.

While you are working on the fuse box, mark then remove the relays and look for melted sockets. These sockets can be purchased from Porsche and although not a simple job, they can be replaced. At a minimum, I suggest that you clean the sockets and fuse box with electrical contact cleaner while protecting the surrounding area. After cleaning, a light coating of Dielectric grease (non conductive) is useful for corrosion protection.

At the battery, there are a number of positive wires and grounds that should be inspected and tidied up. The grounds also warrant a good look. And finally, don't forget connections under the dash and in the center console where the controls reside. The AC system draws a lot of power and every place where a main wire plugs into a component should be felt and if needed, tested for voltage drop between the battery and that point in the circuit.
MC

Q - In spring of 07 I traded my boat for an 88 930 slant nose coupe from Arizona. For the first couple months, I had no problems. Then leaving work one day, it would not start. After 30 minutes of jiggling wires it finally started. After that, sometimes it would start and quit after a couple miles but sometimes it would turnover but not fire at all.

It sat all winter then started right up (but with major exhaust smoke) then I shut it down and left it a couple days. It started again that following weekend, (2 weeks ago) not as much smoke. I pulled it out into the drive and gave it a little throttle (about 4000rpm) just to go to the end of the drive, but when I let out the clutch, I heard (and felt) a very loud backfire and it stalled. When I attempted a restart it turned over like no compression. So now I'm thinking something blew inside the engine. I wait 1 sec. I try it again and WOW Hey MC she started right up!

I want to get out to some club events but I'm still afraid to drive it. A local Porsche mechanic said he thinks it may be the 6 pin cd box, another said computer. What would be your guess without seeing it?

Is there anyone in SEM/PCA near Mt. Clemens area that could stop, look at and possibly fix this without charging an arm and a leg. These days can't afford to lose an arm or leg let alone both. :)

I'm very disappointed with this car so far, maybe I should just get rid of it while I'm still BEHIND :) So brings one more question to mind 3) What is this car worth (if it was running) in fair cond. and almost 100,000 miles.

A - This must be the month for intermittents. Have faith, I am a stubborn German who enjoys a challenge. Over the last few years, a half dozen or so fearful folks have begun to venture far from their “AAA Plus” limit. To me the acid test is taking that long road test myself. To verify intermittents, I built a jumper box that allows me to monitor power to both ignition and fuel circuits and if one should drop out, supply power to the circuit that needs it. You might want to borrow it.

The CD box is not the first place I would look. Usually these fail totally, not occasionally. Far more common is a fuel pump relay failure or ignition cut relay. The turbos have an extra relay in the engine compartment that cuts ignition power slightly after you turn off the key. If you do not feel adventurous in the realm of electricity, I would give up early on this one however. What you can do, is follow the fuse box servicing process that I mentioned to Gary in the answer above. Even if that does not help, always start with the source of power and work your way in.

As far as smoke after sitting, don't worry about it. The engine contains a large quantity of oil that will settle into the crankcase when it sits all winter and that first start up can be very disconcerting. Start to worry when it smokes every time!

Backfiring on this particular Porsche is a particularly troubling and perhaps costly problem. This model uses an archaic fuel injection design that is very sensitive to vacuum leaks in the intake system. Even if a vacuum leak did not cause the backfire, the event itself can CAUSE a new leak. During start up and warm up, the electronic fuel trim components are disabled. In this mode, the engine relies on mechanical fuel mixture control adjustment and vacuum leaks cause the mixture to go lean (not enough fuel) which can cause backfiring.

You might notice the large radiator-like device that dominates the engine compartment when you open the deck lid. This component, the intercooler, is removed during most services and the intercooler is sealed to the intake piping with large silicone rubber O-ring that get oil soaked, broken or squashed. These O-rings are a source of leaks that can cause backfiring and a loss of boost pressure during acceleration too.

As far as selling it, why give up so easy? Once you get it sorted out, you are going to have a ball. Compared to a boat, you are going to have a lot more fun with your Porsche since every weekend there is a driving or social event where you can sport around in your new toy. Besides, what did it cost last season when you filled up your boat? Now double it. Doesn't that Porsche look better?
MC

Q - I have a 1995 Cabrio and the rear window is starting to pucker and pull away from the top. It looks like the glue is letting go. Is that repairable? I got a price to replace the window at about a thousand dollars but the shop said that they would not recommend it. They suggested an entire new top at about two thousand dollars! Help.

A - Sorry to be the bearer of bad news but the top shop is correct. The window is not glued to the top as it appears, it is actually heat bonded during installation of the top. There is a resistance wire that surrounds the window that heats up when voltage is applied. It literally melts the window into the top. Porsche has revised this process and sent bulletins on it but suffice to say, glue won't work as a repair.

As far as the window replacement, the shop was probably recommending against it because it would look different than the rest of the top and based on age, the top is already 13 years old and probably deteriorated. It would not be long before you would have to go back and replace it anyway. For my money, the difference between a whole top versus just the window would make me consider just the window but, as a seasoned veteran once said “buy the best and cry once”.

The newer tops do not seem as strong or as thick as the older Cabs and I like the zippered rear windows too. Durability seems to be reduced on the newer fabrics and the bonded window idea hasn't held up to well either. Too many bean counters? By the way, the price you got on the top seems reasonable to me compared to others that I have researched.
MC

Q - I have a vintage Turbo and the tires are shaking. I think I need a tire balance but I do not want the weights to show if that is possible. What do you suggest?

A - There are a number of factors that affect a smooth feel from your tires and wheel. First, are the wheels true side to side and are they round? Second, do the tires pass the same test? While a bent tire or wheel can be perfectly balanced, the car will still shake.

Assuming that the every thing you can see looks good, then you can proceed to measure the balance. The two types of balance that affect shake are static and dynamic. Think of static as “up and down” imbalance. Up until the sixties, when tires were very narrow, this was correctable by using a bubble balancer, no electronics, no problem, just put an equal amount of weight on both sides of the wheel and you are set. Things have really changed (and now you know when I started working on cars.)

When the famous “Wide Oval” tires became popular a new consideration had to be made that involves “dynamic” imbalance. That is where side to side imbalance will also cause a shake or wobble. This is where hiding the weights can get tricky. With wide tires and wheels, if you simply find the point of static imbalance and put the weight essentially behind the spokes in the middle, you can still get shake.

On tires that need a lot of weight on opposite sides, inside and outside, hiding the weights may not work out to well. In that instance, the tire can be dismounted and rotated on the wheel and sometimes this helps. If you are as picky as me, it is worth the effort. If the tire needs weight in roughly the same spot inside and outside, you have a better chance of hiding the weight. In that instance, the machine can be “fooled” by programming in a narrower wheel and it generally tells you to put a heavier weight behind the spoke.

If you cannot hide the weight (and new Porsches do not have hidden weights) there are European chrome plated “Hershey bar” weights that look (and are) expensive. I have not been able to get the original weights from Porsche so these are a nice option.

How much weight does it take to feel a shake? Glad you asked (oh yeah, you didn't ask). A tire imbalance of 15 grams can be felt at higher speeds. An imbalance of 20 grams can be felt at freeway speeds and an imbalance of 35 or 40 grams will annoy you almost all the time. Clearly the goal is 5 grams or less.
MC

Q - On my 74 911 the crankshaft pulley fell off the end of the engine at about 110 miles an hour! The red light came on and the engine felt like the turbo kicked in. And it is not a turbo. What a thrill.

When I looked at the pulley I can see a hole where a pin would have gone through it and into the crank but there is no hole in the crank. What gives? Can I just bolt the pulley back on without the pin.

A - Randy, the pin hole mushed over when the pulley came loose. First the good news: The crankshaft is hardened and it is probably OK unless you mess up trying to get that pin out. This process will be time consuming since it involves removing the exhaust and rear motor mount bracket just to gain access. Once you can see what you are doing you have to find the hole and the pin. I use an abrasive Roloc disc to clean away the metal that was transferred to the crankshaft during the failure. When you find the remains of the pin, start with a small drill and begin drilling it out. Your ace in the hole is that the crankshaft is hardened and the pin is not. When you get the hole large enough, put a screw in it and pry it out.

So you have saved the crank, you need a pin, and the pulley is damaged. Smart Racing products makes a replacement pulley out of billet aluminum that comes with a new bolt and sells for about $120.00. The pin is the same as a VW beetle main bearing dowel pin that you can get from any VW shop. The crank will need to be smooth and true before you bolt the pulley on and judicious smoothing with the Roloc disc has worked well for me.

About that “turbo boost” effect? The fan and alternator take about 20 horsepower to run at that speed when the failure occurred. You felt the difference between gross horsepower and net horsepower. As far as running the engine without the pin by just bolting the pulley back on? The pin is for alignment of the timing marks and the bolt secures the pulley. You could have bolted it down snug and driven it but then the crank could have been damaged more than it already was. In a third world country, this would have gotten you out of the bush but it is better that you didn't try it.
MC

Q - When I started my Carrera this morning I heard a loud “pop” then the car would not run. It will start but it stalls right away.

A - Chuck, That pop you heard was probably due to an intake system backfire. On an early Carrera, a lean fuel mixture can cause parts to break or hoses to blow off. When this happens, the car will start (on the “cold start valve”) but as soon as you release the starter, the cold start valve shuts off and the engine stalls.

If you have the earlier CIS fuel injection used on normally aspirated cars up to 1983, this can indicate (or cause) a significantly expensive problem. On these models, a plastic plenum directs air flow from the air flow meter to the intake runners. If the car backfires, usually an “anti backfire” flapper valve opens and relieves pressure. This can prevent damage but the backfire can be violent enough to actually break the plenum. Sometimes, the plenum may be leaking air and the backfire is just the “straw that broke the camel's back”. Some cars have the original plenum, the fuel/air mixture weakens the plastic and it can come apart or fractures. In a best case scenario, you find that the glue which secured the flapper valve has failed and it just needs to be re-glued. While you are checking this, see if all the screws are still tight which hold it together. If you find screws loose, tighten all those you can reach and plan to do a more thorough repair since the ones you can't reach are probably also loose.

If yours is an 84 to 89 Carrera, there is a hose that usually pops off near the rear of the engine (where you can't see it). It connects the main air flow meter to the intake throttle body. If you are fortunate, the only thing to do is reinstall the big air hose. The hose is located directly in the middle and top of the engine. Check the clamps that secure it and you may find one loose. If you do, loosen it more and try slipping the hose back on then tighten the clamp. Another source of intake leaks on the later cars involves the breather hoses. These rot due to age, heat, and oil. They are located where you cannot see them unless you remove the air flow meter assembly and If you are willing to go to that extent, plan to replace them since they are now over 20 years old.

On the Carrera 2 & 4, the latest problem that I have seen was an entire intake plenum assembly blown right off the top of the engine. The client said “I think the entire rear of the car lifted up when it happened”. This one was a little tricky. Turns out that when the car had been serviced four months earlier, two of the exhaust side spark plug wires were switched on the right bank. This ignited the intake charge while the intake valve was open. This “human induced” problem that was undetectable during driving the car but on that fateful day, BOOM. There were no apparent long term effects of this problem but it points out the need to mark the things that you remove when servicing your car.
MC

Q - My 1989 Turbo smells like fuel and I am worried that a spark could ignite it. I narrowed it down to the front trunk area.

A - Eric If the fumes are that strong, you bet it could ignite and in the garage, it could take your house with it. First, if you smell this, do not start your car to pull it out of the garage, push it out and look for signs of dampness. The three most common sources that I have seen are a cracked fuel cap gasket, loose screws on the fuel sending unit, or vent hose clamps that are tightened to their limit without securing the hose.

For the fuel cap it's easy. Just pick up a new O-ring for it and you are all set. You don't need to buy a new cap. The part number is 944 201 553 00. The fuel sender screws often take a sixteenth of a turn and usually this fixes them. If you still get dampness or smell odor after filling up the tank, try to blot the area around the fuel sender and see if you can detect fuel or vapor. The sender gasket is inexpensive as well and easily replaced.

On the vent hoses, there is a special type of clamp called “Oetiker”. I suggest that you cut them off and replace them with worm gear screw type clamps which can be purchased a any auto parts or hardware store.
MC

Q - On my 85 Carrera the dome light works erratically on the driver's door and not at all from the passenger's door. Sometimes they work and sometimes not. If I operate it manually, it lights up. Any idea why? I notice that the rubber boots that cover the switches don't look too good either.

A - When it rains, water runs down the “A pillar” where the switches are mounted. The rubber boots keep water out and prevent corrosion at the contacts. To fix this erratic switch issue, remove the rubber boot, unscrew the switch and spray the contacts with electrical contact cleaner that you can buy at Radio Shack. Reinstall the switch and I bet they will work fine. Install new boots (they cost about $4.00) and they will work well for years.
MC

Q - My Carrera 2 just had the clutch replaced and ever since then, there is a funny noise coming from the shifter when I am going very slowly and accelerate. It did not make that noise before the clutch and I am worried if there might be a problem with the transaxle or the clutch work. Is there any way to know what is going on?

A - Porsche used a rubber center clutch disc in many models to minimize noise intrusion into the cabin. My hunch is that you replaced the rubber center clutch with the heavy-duty spring center clutch. The only way to be absolutely sure is to listen with a stethoscope, with the car safely hoisted from the chassis points, while a helper “drives the car in the air” and very gently accelerates up to five to ten miles per hour. If the noise is coming from inside the clutch bell-housing, there is either an issue with the release bearing or it now has a spring-center disc. Try to find out what parts, exactly, were used in the clutch job…if you were not warned about the noise, shame on the guy who sold it to you, but don't worry. The noise may be irritating, but it is not harmful and won't cause any problems. Most enthusiasts prefer the spring center clutch to the rubber center anyway, it grabs a lot better!
MC

Q - On my 85 Carrera the dome light works erratically on the driver's door and not at all from the passenger's door. Sometimes they work and sometimes not. If I operate it manually, it lights up. Any idea why? I notice that the rubber boots that cover the switches don't look too good either. -- Carlos