Oil PSI too high ?????

[pjv911]

I think I may have an issue. I have a 1992 C2 Turbo engine in my 82` sc. The engine sat on a shelf at Brumos Porsche since new. The engine now has only 4k miles on it .
At 3k rpm my fully warmed (210 deg) oil psi is at 140 psi . When idling it sits around 35-40 psi .
When cold it has 140 (thats were the gauge pins anyway) at 1700 rpm and 100 at idle.
I have tried 3 different oil gauges and 2 senders. These are matched to each other (5 bar) and all showed the same results.

As a last test I took the sender and gauge out of my stock 1983 sc cab and installed them . Same readings as the other gauges.
My 83` would only go to 130psi when cold and only 100psi at 6k rpm.

Well do I have an issue ? It is a turbo which has a different oil pump and an extra circuit for the turbo oiling, Also it has factory equipped carrera chain tensioners.
Did the factory install oil line restrictors to bump pressure loss from the tensioners ? Could a pressure bypass valve be stuck from sitting for 15 years ? It had 15 yr old golden clean oil inside. It is 100% perfect in every other way.
What gives ??????

Kurt Williams

[DW SD]

I can't comment as to whether the pressures are too high.

Your oil pressure relief system may not be functioning properly. That is the stack of spring, guide and piston which is veritically oriented and on the right case half when looking from the rear.

I found in my engine (964 bottom end) that there was a burr in the bore of the regulator piston, which caused interference and slight irregularities in action of the pressure regulation. You might remove that an inspect. We ended up honing the burr with emery cloth and then cleaning and reinstalling. There was actually score marks on the piston. After that process, a new piston was installed.

After the burr was removed, it was obvious the piston slid up and down freely. We used a magnet on a telescoping rod to move the piston through its range. If your piston is stuck, it will be tough to remove and actually may require a bit of persuasion from the top to get it out. There is a plug accessible from the top that you can see. It is near the right rear shock tower.

Hope that helps!

Doug

[pjv911]

Do you think the pressure is out of the so called safe range ?

Kurt

[patkeefe]

Kurt, I'd guess you have a restriction in the oil galley somewhere, probably in the regulator piston, as Doug says. If you didn't have a restriction, you could never build up that much pressure. The pistons are steel, and will lock up in the bores after sitting for that long. Are you getting any flow to the front cooler?
Pat

[DW SD]

I'm no expert.

I believe the pressure relief system should reduce pressure to 5.5 bar ~ 82 psi or thereabouts. It is designed to limit pressure.

At some point, you can blow out seals and more (I've heard). It is only going to get worse at startup as ambient temperatures cool.

All you have to do to check the relief piston and assembly is drain the oil and remove the plug. Given the cost of your motor, you can do that inspection in a short amount of time, which is worth it.

Check PET, there is a decent schematic. Actually, the spring is a few $ and the piston only $10, so it is cheap. I'm not sure what would cause it to stick, though.

Doug

[DW SD]

Keep in mind the regulator I mentioned above is within the engine's pressurized circuit. A second regulator is in the thermostat itself to limit pressure in the scavenge circuit. So.....the pump has two chambers, one two scavenge and pump out to the thermostat and the second to pressurize for internal lubrication.

The pressure side is the issue here. When the oil is "dumped" because of the pressure regulator, it actually is fed back into the inlet side of the pressure pump. Seems to me like your oil is not being "dumped.

[Grady Clay]

You are getting good advice from Pelican DW SD.

My opinion is your pressure is too high. You should follow DW SD advice and inspect the oil Pressure [regulating] Relief Valve functioning.

This needs to regulate your oil pressure around 60 psi hot, not 140 psi. Something is wrong.

Best,
Grady

[pjv911]

I dont have pet. Anyone have a picture to help me locate where this regulator piston is ? Is it on the bottom of the case ? I do recall 911 engine cases having a large flat head screw underneath. Is this it ? Is there more than one ? Do I need to remove any components to get to it ?
On a good note I suppose the high oil psi is robbing hp too. Maybe I will free up a few ponies with this repair.
Im not going to have the chance to look into this repair until after labor day . I will be relaxing my tired body in the Outer Banks (N. Carolina) for 9 days. I will be on pelican during this time(beach house has internet access).
When I return I will also be installing a modded fuel dist I just got from Imagine Auto. At that time I figure I will know where this relief valve is located.
I appreiciate these quick responces guys . Usually I get a cold shoulder for a few hours.

Pat , the front cooler gets flow after about 15 minutes run time. I have a temp regulated fan on a B&B fender mount cooler. The engine has no cooler on it (from the factory like that) . Instead there is another oil filter there. Do you think 15 minutes is to long to come up to 180 degs ? I know it holds alot of oil but 15 minutes seems very long before it passes through the only cooler on the car. Grady , whats your opinion here ?

Kurt Williams

[Bill Verburg]

Search is your friend

previous discussion

I know that you tried a different guage and sender, but I also know that a new sender and old guage will read ~2x real pressure.

maybe try a diagnostic guage?

[pjv911]

Originally posted by Bill Verburg
Search is your friend

previous discussion

I know that you tried a different guage and sender, but I also know that a new sender and old guage will read ~2x real pressure.

maybe try a diagnostic guage?

I was aware of that 2x thing too. Thats why I swapped in the gauge and sender from my 83` and used them at the same time. Still got the same results though. I will check that link. Thanks Bill

Kurt

[rusnak]

wouldn't oil be plowing out of the breather hoses and o rings, pistons seized or rods bent, etc if the oil was at 140 psi? That just sounds like a lot of pressure since the oil bypass is supposed to kick in at what 80ish psi or so?