KYWes

Patient: '95 Z28 M6
Recent work: Melling 10554 oil pump, pump drive shaft, GM pickup, right head gasket, Comp Cam camshaft kit, oil sender unit.
Fresh 5w-30 oil & filter, full oil level, less than 25 miles after above work.

Pressure is so low at idle it sets the check guages and service engine soon lamps.

Pressure at first start in morning, 40psi at idle.
After warming up follows typical guidelines 20 psi at 2,000 rpm, 25-30 psi at 3,000 rpm.

It's always showed low at idle but never set the check gages lamp.

Suggestions?

shoebox

Low oil pressure won't cause a SES-only the check gauges light. What spring did you use in the 10554 pump? Typically, worn bearings are going to be the cause.

KYWes

I left the stock spring in it (pink?).

Bearings, hmmm, the answer I suspected but didn't want to hear.

I'll add that miles on engine is 143,800.

KYWes

I think I'll check with a mechanical gauge to be sure.

Can bearings be replaced with the engine in the car? Never mind, found the answer with search.

Fatdog2

I would try a straight 30wt oil and see if that helps.I here 4 quarts of oil and a quart of hyperlube makes a difference on a high mileage engine.Do a search.Hope this helps.

bw_hunter

Oil pressure is primarily controlled by the cam bearings which I don't think can be changed out with the engine in place. If it is possible, it certainly would be very difficult.

If the mains and rods are very worn you can see a drop in oil pressure as well but you'd probably hear a rod knock if that was the case....

Using thicker oil would certainly help you diagnose the problem as being real...and not just a gauge problem.

Dmonty

Pull out the dipstick and run some oil on your fingers. Get it in the sun light and see if you see glitter. If there's glitter you have a bearing problem. If you see no glitter double check with the oil filter. Take it off and cut it open, have something ready to pour it in too. If there's glitter anywhere it would be in the oil filter. If you have glitter it's a bearing problem.

KYWes

Changed oil yesterday to 30w Pennzoil + Hyperlube. Pressure was better. Still went low at idle but not as low and not low enough to illuminate the check gauges light. Engine seemed quieter too. Will monitor.

Injuneer

Now you have increased the wear on the engine at cold start. The purpose of the "5W" or "10W" is to provide improved circulation when the oil/engine is cold. Once a 10W-30 oil warms up to normal engine operating temperature, it exhibits the required viscosity to fall withing the SAE specifications for 30-weight oil at 100*C.

A better attempt at a "band-aid" would have been a 10W-40 oil.

KYWes

Yeah, I understand oil viscosity and blended oils. I went ahead with this change for several reasons but primarily because I won't leave it in there as long as a regular oil change.

jjbmxer

I run 10w40 in a 95 with 153000 on the odometer

87Aerocoupe

I have the same problem in my 97 SS with 133xxx miles on it and I have already begun building a new all forged engine for it with a bunch of LT1 parts I had lying around the house. I knew exactly what the problem was so I don't drive the car much at all, just waiting for the new engine to get done.