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The Master Cylinder Porsche 356 Tips: Index  Axle Boot Installation Intermittent No-crank Symptom
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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 |
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Q -
I 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 |