Oil pressure reading is wacked - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 08-17-2007, 09:44 AM   #1
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Default Oil pressure reading is wacked

My problem is once my car warms up, the oil pressure drops from 40 to redline. As I go faster it will stay around 40 but as soon as I slow down it drops, and while at a stop light it stays in the red. So I searched through the threads and see that using a Fram oil filter can sometimes cause oil pressure problems. I did have a fram and replaced it with a Mobil 1 High Perfromance. It was more expensive, so I figured it must be better right? My oil pressure sensor is a Delco sensor and was replaced in/around April by my Dad. I changed the oil last night with 10W30 and the new oil filter, and although the pressure looked better when it was cold, it still dropped a few mintues after driving it on the road. I would assume that this means the oil pressure actually is poor, and not just an indication problem?

Some history, this car had the crank turned and new oversized bearings installed back in Feb of this year, and it has new bearings and rings throughout. The car has 200K, but the engine is a junk yard engine with about 75K, and my dad went through it and cleaned her up. The indication problem started a little over a month ago. Does this mean an Oil pump is going? Do they go slowly like that or do they usually just go? My experience with oil pumps are on older cars from the 60'* when they were basically mechanically driven with 2 big gears. I assume they are different now? Any help would be greatly appreciated.
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Old 08-17-2007, 10:35 AM   #2
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Our oil pumps are in the timing cover and driven by the crank. They don't have many moving parts and don't wear like a typical pump.

I have heard that some have troubles with changing bearings etc and failures on the 3800'* however for each problem there are plenty of success stories. It does sound as if your bearings are wearing. Do you have any grayish streaks in the oil when you change it?
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Old 08-17-2007, 11:19 AM   #3
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Nope the oil looked fine. I replaced it almost exactly 3000 miles ago, and I would say it looked typical for that long. So you're saying that oil pumps don't really go bad? Low oil pressure is bad bearings?
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Old 08-17-2007, 11:20 AM   #4
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I'm saying...

Oil pumps don't typically go bad. To emphasize this..call around to some parts suppliers and dealers asking for price and availablity on the pump.

Low oil pressure is typically ... bearing..not always.
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Old 08-17-2007, 01:06 PM   #5
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Have you hooked it up to a mechanical oil pressure gauge to verify that it is reading properly? The 92-95 gauge clusters are known for the board that controls gas, oil and Boost/voltage to go bad giving wacky readings. That isn't a hard fix to do, but you can really only verify it by either a mechanical gauge to tell you everything is fine with the pressure, or finding a good board and replacing it. The first option is the recommended first step as it removes further doubt about the oil pressure.
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Old 08-17-2007, 02:21 PM   #6
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Never checked the oil pressure manually before. Is there instructions somewhere in the tech archives of this site? My Dad has several pressure checking gages, but pretty sure they're fuel pressure checkers. I wouldn't even know what the pressures should be at what RPM
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