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Go Checking For Corrosion Under Your Oil Pipes. Do It Now.

I’ll bet you there is no corrosion on my 911. That’s me two weeks ago. In fact there was. It was not serious, but it would have become, if I hadn’t found and fixed it this or next year.

We all know that when it comes to rust, at the original 911 the crucial spot is the place where B-pillar, rear fender and door sill meet.

This is even worse on the right side, as here the crucial points are hidden by oil pipes and oil thermostat. Removing these little s*****s to look behind is not an easy thing to do. In the rear fender, in the cavity in front of the wheel, we find two huge nuts that connect the feed flow and return flow pipes to the thermostat. The pipes pass to the front fender under the door sill and there they join the oil cooler, again connected with two nuts. Originally made of brass, after three or four decades, the threads of these nuts will be heavily corroded and they won’t open easily. After two hours of pointless trying, I went looking for a saw and cut them out and in fact, when I clamped the thermostat into a vice and used brute force to open them, the thread broke instead of coming loose.

A set of new pipes and a new thermostat add up to 1.000 Euro roughly and at least I can say that the new ones look awesome when built in.

My 76 911 S doesn’t have a real oil cooler but that brass pipe cooling loop which I could save by some endless hours of wire wheeling.

The corrosion.
If you use your car on a regular base, it will be hard to avoid that the little spaces between the oil pipes and their supports, the door sill and the fenders fill up with dirt and stuff. Once wet, humidity will stay there for days. It’s great that all these panels had been galvanised by Porsche from 1976 on, but at some point all the zinc will be eaten up and in my case this happened around all three supports of the oil lines.
I’ve diligently wire wheeled all the rust off, filled up the missing pieces with PU sealant and covered it all with a thin layer of stone guard, followed by a layer of Oak Green and some two-component clear coat.

Before reassembling, let’s not forget to add some new wax oil to the spot mentioned above.

Re-installing the oil pipes is tricky.
There’s just not enough space to tighten the nuts of the thermostat.
I’m sure there is a best practise to assemble the whole system and I’m sure that many of you succeeded in different ways to bring it all together. Here’s one that worked at my end (after four or five others that I tried unsuccessfully):
First install the pipes and screw them loosely to the body. Then add the thermostat and tighten the nuts as much as you can using your fingers only. Next mark the position of the thermostat relatively to the return flow pipe, then remove it all again. Outside the car, attach the thermostat to the return flow pipe and tighten it firmly. Then install both pipes again and finally tighten the nut of the feed flow pipe to the thermostat.

Connecting the front ends of the pipes is much less a problem.

3 additional images. Click to enlarge.


2 responses to Go Checking For Corrosion Under Your Oil Pipes. Do It Now.

  1. dont know about the condition of your 2,7 Liter Engine but the stehbolzen of the zylinderheads tend to get loose with that engine block with age and wear. Just if you want to get deeper into the nineelevens weak points. But before you disassemble your engine lets photoshoot with my mr2 ☺️
    cheers from the westcoast starnberger see to the westcoast ammersee

    • @GinTonic
      Thanks, mate. It’s so funny, whenever you say the word “twopointseven” people shout “stud” or “Stehbolzen” at you.
      In fact, yes. All 911 have a weak point there and it appears that the magnesium block 2.7 stand out in a negative sense. Let’s hope for the best …

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