The Master Cylinder Porsche 356 Tips:

  • Axle Boot Installation

    Q – I have an oldie but goodie, a 356 with a Super 90 motor. Last time I hoisted it up, my buddy said that my axle boots were installed wrong. Naturally, since I installed them, I was embarrassed so we bet on it. I bet that the seam should be up to keep the oil in and he said it was supposed to be horizontal. Who pays, him or me? I have a six pack riding on it. Tom

    A – Sorry Tom, You lose. It is counter-intuitive, but the seam should be horizontal, not vertical. The boot has to flex and bend. To do this the seam has to follow the arc of axle movement. Imagine trying to bend your finger sideways. No worries though, just share the six pack with me. MC

  • Intermittent No-Crank Symptom

    QI know this is an odd problem but I am at my wits end. I have an antique 58 Porsche and it will not start reliably. I have replaced the starter, the battery, wire harness, and ignition switch but sometimes it still won’t crank. Got any ideas? I spent a ton of money on it already.

    A – We call that “firing the parts cannon” at the problem. You probably needed all that stuff anyway but my guess is that you probably are not getting full voltage to the solenoid. The cure may be simpler than you think. The cause of the symptom can be found by a qualified auto electrician who is skilled in voltage drop testing. To energize the solenoid requires a strong electrical signal. For any electrical device to function, you must have power and ground without excess losses. Many people install a relay as a quick fix or “band aid” rather than finding the problem. Although this may cure that symptom, it may not address the other symptoms of voltage drop such as dim headlights, slow wipers, or headlights that pause between high and low beam, etc. Problems I have seen are incorrect or corroded ground straps, loose bolts to the ground strap, faulty main battery cable (it is quite long), sleazy emergency cable ends, poor crimps, and old terminals that simply will not carry current. The key word is current. If any of these components will not pass current under load, you lose voltage. I have been fooled (and embarrassed) by a brand new ground strap with a new bolt that was screwed into a rusty bracket bolted to the frame. With an electrical meter you can check resistance and voltage. And although it can seem fine, when you load the circuit, it just won’t cut the mustard. At Bosch Service Training, they no longer recommend resistance testing or voltage testing alone for heavy load circuits since it has proven unreliable. Loading the circuit and measuring actual voltage drop is the only way to know where the problem lies and confirm that it has been repaired. I was recently asked to assist in a horn diagnosis. All the usual problems had already been corrected. The technician replaced the horn, cleaned the horn contacts replaced terminals at both ends of the wire (and spent a fair amount of time doing all this) before testing for voltage drop. Although the wire looked fine externally, it lost 1.1 volts under load when the horn was honking. When he wire was replaced, the voltage drop measured .3 volt and the beeper blasted again. MC

  • My 356 wanders on the highway

    Q: My 356 wanders on the highway. It really is a chore to keep it in a straight line even though it has been fully restored and aligned. My mechanic says everything feels tight but I have to wonder…why does it feels so loose?

    A: The most common problems that I have seen on these cars are incorrect tire pressure, worn king and link pins, and worn tie rod ends. Tire pressure is a common issue not only on 356’s but on all cars. Use the vehicle manufacturer’s recommendations for pressure. Do NOT rely on the info that is printed on the tire since those values are for maximum load and have nothing to do with your car. King and link pins can be checked with the weight off the car by grabbing the tire top and bottom and viewing the side to side play in those parts. Link pin wear can be adjusted and they often need to be adjusted. King pin wear can only be corrected by replacing the pins and bushings. Recently I discovered (by a vendor error) needle bearing link pin kits. If you need to replace the king and link pins, these “heavy duty” link pin kits are pretty slick. Tie rods are a very common problem since checking them is traditionally been done by wiggling the wheels back and forth while the car is jacked up. While checking them this way may detect grossly worn tie rod ends, the method I use is to compress them between the top and the stud with a pair of large “Channel Lock” pliers. If you detect more than a sixteenth inch of wear, I would suggest that they be replaced. Some cars I have inspected have over an 1/8 to 1/4 inch of movement. When a tie rod end is worn, once the car is on it’s weight, the steering will feel loose even if it felt okay when it was jacked up. MC

  • 6 volt 356 Charging System not up to the task

    Q – I have a ’64 Porsche 356C Coupe — 6-volt — that has an electrical system that’s not 100% happy. Apparently the charging system is not quite up to the task as a month or so ago I drove to Columbus for an event and half way through the weekend had the battery down enough that it wouldn’t restart the car. Fortunately, two 6v Optima batteries fit where the original lead-acid goes so I carry a spare. It happened again last Saturday at Woodward — stopped for gas and no restart. I’m not an electrical wizard and am looking for help. Up for the task without costing me a fortune? – Chuck

    A – That spare Optima is a great idea! Every August I get the same calls, “I stopped at the store, came out and the car won’t crank” And when the car is left to cool off, like a miracle, it starts right up! I feel fairly well versed in these problems and I suggest solving it scientifically…by testing. The 5 volt charging system is a serious problem that enthusiasts face with the lack of reliable parts. The current challenge is a lack of 6 volt regulators. Even NLA who is an acknowledged leader in 356 goodies has been flummoxed. Many who want to drive their cars regularly opt for a 12 volt conversion. Parts are much more readily available. Rather than burn more ink in this column, go on-line and access all the P4 articles on this and many topics at the SEM/PCA website. Good luck and remember, a fortune is a relative thing. Ask anyone with big 3 stock. MC