Oil pressure too high

[Jeff Jagusch]

I rencently finished putting my 911 back togehter after a long resotration. The engine I installed was a recently rebuilt 3.0 from a '79 SC (5000 miles from previous owner). The car runs great but???? the oil pressure will climb over 100 psi HOT.
The other problem is that the temperature will climb steadily to 230-240 just normal driving (even with front fender Carrera cooler). I suspect the engine monted thermostat is not opening.
Could this be the cause of my high oil pressure??? I've grounded the car until I can get this resolved.
Also, I just replaced the pressure bypass psitons with the updated parts, with no change in pressure.
HELP

[Early_S_Man]

Jeff,

Your engine shouldn't have needed new pistons!

There are two updates:

For 1976 production, the pistons were changed from perforated to solid with a shallow groove around the periphery of the piston skirt. And, the 2nd, vertical valve in the right case half changed from dumping oil into the sump to going right back into the supply line port of the main pressure pump.

Some time in the '80s, instead of two 70 mm springs, the second, vertical spring was changed to a smaller diameter 86 mm spring, and a tubular support guide was added that fit inside the longer spring.

The only update your engine should have needed was the 86 mm spring and guide!

Have you verified that you truly are reading the correct oil pressure?

------------------
Warren Hall
1973 911S Targa

[al lkosmal]

I know this is an old thread, but I am working on a project that is exhibiting these same symptoms. What was the cause and solution?

regards,
al

[Autoban]

I don't know what the fix was in this particular case, but first thing when you change engines you need to check that the pressure and temperature sensors are the correct fit for the gauges you have in the car. 100 PSI equals 6.9 Bar, my 3.2 L maxes out at 5 Bar on the scale). You may have a 10 bar instrument, but run it with a 5 bar sensor, this could give you the high reading.

Worthwhile checking.

Juergen

[al lkosmal]

Juergen,
That is good thinking and has been checked. The gauge is from a 3.2 and the current engine is a 3.6. It has a 5 bar sender in it, as I took it off of the original 3.2 engine and installed on the 3.6. I swapped to a 10 bar, just in case, but no change in the pressure reading. This has since been measured with a mechanical gauge and the high pressure has been verified.

regards,
al

[shbop]

signing-up.

[KTL]

Well the engine's oil pressure is dictated by the bypass piston and the overpressure piston in the engine case. I'd check those to make sure one isn't stuck.

Ultimate Oil Pressure Relief Valve Thread

[porschetub]

Originally Posted by al lkosmal

Juergen,
That is good thinking and has been checked. The gauge is from a 3.2 and the current engine is a 3.6. It has a 5 bar sender in it, as I took it off of the original 3.2 engine and installed on the 3.6. I swapped to a 10 bar, just in case, but no change in the pressure reading. This has since been measured with a mechanical gauge and the high pressure has been verified.

regards,
al

I found the same and don't know why,you would think with the wrong range sender the gauge reading would be incorrect.
I also put a mechanical gauge on and found the readings to be within a few PSI of each other.
Strange that the oil pressure isn't falling off with those higher oil temps,I can't remember the oil flow schemetic but would this not indicate the oil isn't diverting to the engine cooler after warm-up ??.

[cmcfaul]

Pull the engine thermostat and test it. Not difficult. That should solve the heat issue as it is likely stuck (hopefully). Otherwise, there is an obstruction somewhere which would also explain the high pressure.

Maybe you can warm the car up and follow the oil path with an infrared temp gun and see where the temps change indicating where the obstruction is.

Chris