I have put a motor (2.4) that was in perfect running order 13 years ago into service again. It had great oil pressure when it was removed. I stored in a a shrinkwrap and turned it over by hand every couple of months.

I've noticed that the oil pressure when cold is great (70# @3K). After it gets hot it appears that the oil pressure only runs about 20# at 3K. I've also noticed that the oil pressure guage, every now and then, will jump up to 40# for a second and then back down again.

I've replaced the sending unit, but it still seems to do the same thing. I'm going to replace the oil thermostat next (because it's easy). I've also got 2 new pressure relief valves/pistons to replace.

The question I have is: where is the second pressure relief valve? I know about the one on the bottom of the case. Can I get to the second one without removing the motor?

Thanks for any advice you can give me. Rich Lorenz

[matt de maria]

70 pounds is not that great cold. Save yourself time and put a mechanical oil pressure gauge (for testing purposes) in the electrical sensor's hole.

[matt de maria]

Forgive me for not explaining. By hooking up temporarily a mechanical gauge, you will find out if the perceived problem is in the gauge head or wiring harness.

[Marc A]

Right crankcase looking from engine bay is vertical PRV & Left crankcase is horizontal PRV.

Both can be removed with engine in the car, although I can't remember if the H/Eers have to come off.

Thanks for the replies. The left H/E has to be removed in order to get to the horizontal PRV. I've also noticed that on occassion, the oil temp and pressure gauges go crazy (temp pegs high and oil drops to zero). I suspect the ground since I can rap on the gauge and it all comes back to 'normal' for a while.

I was also wondering if a pressure sender from a '73 motor is compatible with a '81 pressure gauge?

Thanks, Rich

Matt, I think 70# is pretty good. If each mark on the pressure gauge is 14.5 pounds and the gauge reaches 5 on a scale of 6, that would seem like an acceptable pressure in my book. Am I wrong? I mean how much higher do you think it should be? Rich

[matt de maria]

Two things:
On a cold engine the oil pressure will normally rise to the bypass value and stay at that value (at 5k rpm). ( I am also assuming that the 70# value is not at idle). For a warm engine (175F oil temp) I would expect the oil pressure to reach at least 100# (at 5k).
Secondly if you tap the gauge head and the oil temp and pressure fluctuates, I would look for a miscalibration factor there first. That is why I said to hook up a mechanical gauge first to ascertain what are the real values. This will give you a direction of what to fix first.