WTH, oil pressure drops like a rock past 4000rpm
02-12-2007, 05:40 PM
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WTH, oil pressure drops like a rock past 4000rpm I noticed today that sometimes I get on it and the car revs past 4000 rpm the oil pressure drops. Its weird because the car only does it sometimes. I can romp on it and pressure climbs normal, or it will flutter. Sometimes after I get on it the pressure reads low at idle, I'll shut the car off, get gas, and then it reads normal again when i start it back up. It sometimes flutters at normal driving, or can drop at idle. It can also be perfect. No knock or other sounds coming from the car, it did make what sounded like an exhaust leak tick after I romped it once today to check, but it went away almost immediately. Ran perfect on the way home despite the lower pressure at idle than normal. Sound like the oil sending unit? Not sure what else it could be, when a bearing goes the car usually runs like crap consistently. Opinions? I did a search but did see anything said about the pressure fluctuating only when you romp on it.
02-12-2007, 06:05 PM
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It sounds like your sender is getting flaky or you are starving for oil at high rpms. First thing is to get a mechanical gauge and find out what the pressure is really doing.
02-12-2007, 06:07 PM
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Just checked the oil and everything seems OK, I am really worried that I might have hurt something with it dropping like that. Going to go change the oil first thing tomorrow and see what happens, with the tick disappearing today it is making me think that maybe the lifters didn't pump up because it got starved for oil. Which again makes me nervous.
02-12-2007, 07:34 PM
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YOUR OIL PUMP IS JUNK! My car did that for a few years, I allways passed it off as just a gauge problem. It seemed to have no effect on the engine untill one day I backed the car out of my garage to notice the check gauges light was on. I looked at the oil PSI and it was on Dead Zero! I put the car in the garage and cranked it over without the oil filter on it to find no oil squirting out. I tore the front of the engine down to the oil pump. I then removed the pump and found the plunger in the oil bypass valve totally stuck. I had to punch the plunger out with a screwdriver and alot of force. My car is an 01 and I was told the defective oil pumps where corrected by the 01 model year. Well they were wrong. The front of the pump had a "00" date stamp right on the front of the pump so it was an older pump. I replaces it with an "06" LS6 oil pump, and while I was there, an LS6 cam....and heads! Threw it all back togeather and it never showed pressure dropping at higher RPM's again. I think at higher RPM's, the plunger gets stuck up in the pump, and wont let the oil circulate. The car ran for about 2 minutes with no oil pressure before I noticed the check gauges light. Since the oil pump swap, I have put 6000 miles on the car with no problems, or pressuere drop. And I couldnt be happier with my mods, maybe its time for you to do a oil pump swap! Any questions, let me know.
-Dan
-Dan
02-12-2007, 07:56 PM
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pressure drop at high rpm is notorious when you're low on oil. Also could be the gauge, sending unit or oil pump. Start with th oil level, then replace the sender..if that doesnt work get a mechanical gauge...if that doesn't fix it, test the oil pump... and so on.
02-12-2007, 08:13 PM
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Thanks guys all is well, I just changed the oil to GC 0-W30 and pressure problem is gone. My car didn't burn a drop of oil before the Heads and Cam, so I didn't expect that to be the problem. Brand new ported pump in there so I knew that wasn't it. It barely read low so I think I just need to keep a good eye on it. Car makes no bad sounds and no ticking. I think I lucked out and didn't really starve it bad, I only went full throttle maybe once or twice before I noticed because I am always looking at the oil pressure when I run it (thanks harlan shift light). It never seemed to drop below 40 PSI for more than maybe a second and dropped progressively and went right back up on the shifts. So it looks like a dodged a dead bearing bullet!
