Questions and Answers

Isuzu Trooper II Low Has Oil Pressure? Q. I hope that you might be able to help me with a problem I'm having with my 1989 Isuzu Trooper II 2.6 liter 4 cylinder. I installed new main bearings, rod bearings and rings in the engine and put a head on it off of a 1988 Isuzu Trooper that I had the valves replaced in. I also installed a new oil pump.

When I started it up it had good oil pressure to start with but as it warmed up it dropped down to approximately 10 to 15 psi.

I replaced the oil pump with one that I took out of the old engine and it was still the same. I replaced the oil filter, installed a mechanical gauge and still the same. I've had two different sending units on it. I bought a short block and installed it and still have the same problem. I even replaced the oil filter mount with the by-pass in it.

I replaced the cam to try to see if that had any effect which it didn't. I finally replaced the oil pump with a new one again and still have the same problem. Please Help, I'm totally mystified.

A. 10 to 15 psi at idle is about right. As long as you have between 25 to 80 psi at 3,000 rpm. you're good.

You'll get high oil pressure at idle when first started and it is normal to come down as it warms up. Also, keep in mind as the engine breaks in the oil pressure will rise as everything seats in.