Engine/Transmission (1994 - 1998) oil pressure gauge

[JRS]

Since it was new, the oil pressure gage on my '97 hasn't moved around much. Didn't matter if it was at idle or under full load, it always hung out around 40 psi. there was some minor flucuation, say leaving from a stop light, but never more than about 5 psi. Didn't matter if the oil was new or in need of changing. Now, with 117,000 miles on the odometer, suddenly the oil gage is flucuating like you would expect it to. it drops down to about 25 psi at idle and then comes up to about 45-50 psi under acceleration. I changed the oil, but it made no difference. (I have always used Fleetguard filters) The engine sounds fine, and the dipstick checks out just fine. I'm not too worried about it because I used the rule of thumb for oil pumps that we use in racing, "10 psi of oil pressure per thousand rpm's of engine speed". Just thought it was strange that the gage started finally moving. Any Comments?

 

[y-knot]

I know of the rule you are talking about, But I do not think it would apply to the diesel. We only see top rpm's of 2200-2400 rpm, and I would not be very happy with only 20-25 psi at those levels. Our eingines see huge bearing loads and oil pressure is critical to survival. I wonder why you never replaced the oil sender unit, you knew it wasn't acting right? I think I would start with that. I monitor both oil pressure and temperature, At start up oil pressure is well over 75 psi at idle, pegs needle (100), till warm, then on highway stay's in the 50-70 range. And hot Idle is between 30-40 psi. Oil temps always in the 150 range for normal everyday driving.