High Oil Pressure

SCrazy

SCCoA Member
I noticed something different the other day. Car used to cold idle at 75psi oil pressure then drop to 45psi or so when hot. It no longer drops hardly at all when hot.....maybe to 70psi. Replaced the oil filter and verified the gauge with a mech gauge attached directly to the pressure port.

Any ideas what could be up???
 
I thought the bypass opened under excessive pressure and was closed under normal conditions. I'm not sure what pressure that thing would open at or if it could fail in a way that would be a restriction to flow....I'm assuming it's a restriction somewhere.

I first noticed this after I removed the oil cooler but I can't image how that would have anything to do with it.
 
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If the valve sticks closed then the pressure would read high and near constant. Whenever open, it bypasses more oil. I don't have an oil cooler, either, but that wouldn't affect oil pressure.
 
If the valve sticks closed then the pressure would read high and near constant. Whenever open, it bypasses more oil. I don't have an oil cooler, either, but that wouldn't affect oil pressure.

The pressure starts at 75, drops to 70 when hot then climbs to 80 at high rpm. Maybe you guys are on to something.......
 
If it doesn't go above 80, then I'd say your relief valve is working. At least on the high pressure side of things.

Is your car getting as warm as it did when the pressure dropped lower?

By the way, all you multiple-engine builders, where in the oil passage circuit does the factory pressure port read the pressure (in relation to the relief valve)?

I assume it is at the beginning, but are there any major pressure-drop areas that the oil meets before getting to the sensor?
 
The gauge reads relieved pressure. If the relief valve is jammed up, it will bypass a fixed and constant amount of pressure. That's why it seems to stay constant. We didn't say it was stuck closed.
 
The gauge reads relieved pressure. If the relief valve is jammed up, it will bypass a fixed and constant amount of pressure. That's why it seems to stay constant. We didn't say it was stuck closed.

I would think that if it was stuck in any position that the oil pressure would change according to the temperature of the oil though. Or is the oil pressure range we see (normally) due to expansion/contraction of the actual relief spring and cup while varying temps?

This is a confusing topic for me. :eek:
 
if a bearing shifted the oil pressure would still be normal..there are multiple routs oil can go. unless all of the bearings shifted. if that were the case then there would probably be a lot of rattling going on and the engine would have siezed up by now.

and this high oil pressure issue is sudden? other than removing the oil cooler what did you do?
 
maybe it was the new oil you filled it with. could be thicker and less viscous causing high pressure. I also just read a thread about high crankcase pressure causing high oil pressure readings, caused by a bad pcv.
 
before you go tearing into motor go and get a new oil filter.

can you still install the stock size filter or did you change that?

i rember seeing a nissan 240sx that had some thing wrong internally (like collapsed, defective) and had same outcome. but pressure was through roof, but not going to rest of motor...

that would be the first thing i would check/replace and test again before taking front cover off.
 
After I first noticed the high pressure I changed the oil and filter thinking maybe a bad filter.....the problem remained. The first filter had been on the car for a while before the problem started.

The filter is stock size I just removed the oil cooler.
 
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