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[chuck21401]

I needed to change the oil in my 931 so I decided to check on the oil pressure spring...and bought one from the Ebay seller mentioned above. I've noticed that my oil pressure seems a low at idle when warmed up, though the warning light stays off.



Interestingly, the old spring was 3mm shorter than the new one. The part number is matches PET, so I believe that the new spring is the right one. The car is still on jack stands, so I haven't had a chance to run it yet.

Also, it's important to note...that even though I had pulled the plug from the oil pan and let it drain...a good amount of oil came out when I removed this assembly. So just be aware of that. Here are some pics.

Here's the bolt that needs to be removed. 17mm.


Here's what it looks like with the oil pressure relief assembly removed.


Here's the hollow bolt, piston and springs. 2 new ones + the original. The sealing washer that was there didn't look original; a new sealing washer is in the bag above, sourced from FCP Euro. I don't know why they sent 2 springs. I have an extra is someone needs it.



The old spring measured 53mm


The new spring measured 56mm

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1981 Porsche 931 w/S1 engine & euro g31 transaxle. Water-cooled intercooler

[Cedric]

I can see that i promised a post about the springs earlier (in 2022 ) in this thread, time flies

I took apart two old oil pumps. One were an s2 that i rang for years and the other s1 i think, not that it should matter. But both had different spring winding design, and lengths(by design or relaxation i dont know). The one I call the long one is the one i bought new.



The shortest was 52,5mm
Middle 54,5mm
Longest: 56mm

I also measured their spring rate since they all had different winding types.

Shortest 3,96N/mm
middle 3,89N/mm
Longest 3,18N/mm

With the current length they had, the seat pressure that the oil would have to overcome before starting to bleed was:

Short 12,9N
Middle 25,5N
Long 30,2N

So the conclusion is that they are quite different, also that you can have a really weak spring in there without knowing it, the weakest one i had for example would start popping open at half the pressure to the new one. Its also a bit strange that the rate is different which will alter the opening characteristics.

Anyway my engine with the new spring has had really strong oil pressure so far, so i havent seen anything strange, only race track testing left.
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1980 924 Turbo
www.instagram.com/garagecedric/