View Full Version : Interesting problem with Oil Pressure.

09-01-2004, 02:21 PM
Ok... qucik overview...

Changed oil
Had problems with filter "spewing" it was on cockeyed... fixed it.
Drive to school today
Oil pressure at idle was 50+ psi at idle and during acceleration before shifts it would go to 90psi then fall back to 50psi or so when car was shifted. Its 8 miles on the interstate at 70mph on the way to school FYI. I look down to see my oil pressure in 4th was at 50psi but I was a 3400rpm. I pull over just to make sure the filter wasn't spewing or anything, no leaks that I could see. At idle the oil pressure was around 25-30 psi. I think hmm and I carry on to school very cautiously. The car seemed to run fine but at the point before I shift, the PSI was only at 55psi or so and then it would fall to 35ish psi. I know this is confusing... what would cause this sudden drop in oil pressure and also, what is "normal"

Thanks a lot. Any tips will help. I'm at school in my computer class so I have until 2:45 to figure this out. Maybe its something that will go away? I don't know. I hope to find out what is causing this and then fix it.


09-01-2004, 02:36 PM

What you're seeing is 100% normal.

Oil pressure drops as the car gets warm. The most important oil pressure number is "warm idle," which is the gauge reading after the car has fully warmed-up and the car is just idling. This number on a TR6 should be around 40ish, but it's not uncommon for it to be around 30. If it is 20 or below, you're looking at an engine with pretty low compression on one or more cylinders. (A worn engine.) You can run a TR engine that's low on oil pressure for a long time, you'll just need to clean/replace oil-fouled plugs every 100 miles or so!


Rick O.
09-01-2004, 04:18 PM
Couple of possibilities: your oil pump pressure relief valve (PRV) is stuck partially open or you are witnessing rapid destruction of one or more main bearings. Bearings can be destroyed in a matter of miles due to insufficient oil flow and you can watch the pressure gauge drop during the destruction. What's your coolant temp gauge telling you? Pull the dipstick; can you hold the bottom of it comfortably or is it burning hot? Watch both the pressure & temp gauges carefully on your ride home.

Let's hope it's a stuck PRV.