Oil pressure fluctuationn on my camaro


#1

My son has a 2001 camaro 3.8 liter v6. I recently replaced the upper and lower manifold gaskets. Now, I am getting wild fluctuations with my oil pressure. It will read 90 pounds-plus one minute then drop to virtually nothing the next. I’ve replaced the oil pressure sensor twice. The first time it was reading close to 90 pounds.The new sensor has it starting with a pressure of more than 100 pounds. But then it will drop to 40 pounds after driving for about 45 minutes to an hour. I’m not sure what is going on. Any suggestions?


#2

I’d guess your problem is not mechanical but electrical.

Temporarily install a mechanical oil pressure gauge in the sender’s hole. Drive the car around with the gauge taped so you can read it while you drive around to confirm what you are reading is real. My guess is that what you read on the factory electrical gauge is not real, it is a wiring problem in the oil gauge circuit. Look for bad grounds, damaged insulation and shorts first. The gauge in the dash panel may also be bad.


#3

Were you super careful about scraping the old gaskets and not getting any chunks in the engine?


#4

Concur w/advice above to test this w/a shop gauge installed, don’t rely on the dash gauge until you know it is working. If you actually are getting oil pressures that high it can cause some problems with hydraulic lifters. The oil pressure pushes so hard on the lifter the valve doesn’t close properly. So if this is associated with a poorly running engine, that’s something that confirms there actually is an oil pressure problem.

Edit: You aren’t running a thicker oil than is spec’d for the car right? LIke a 20W-50? And this is the original oil pump, not a high volume racing oil pump installed after buying the car?


#5

Not sure if there are stepper motors n the cluster, the advice is good, but the observation could be a stepper motor issue, not a real issue. PS in my 03 gm the oil pressure gauge is not oa real sensor of oil pressure, just what the brains think the oil pressure might be. The idiot light is the real indicator of low oil pressure.


#6

Nope. running 10w30 as specified on the cap. The car is running fine, other than slight miss while at Idle. I believe that is the result of a vacuum leak that I haven’t been able to find. It doesn’t have any kind of knock. It does have a coolant leak that I can’t find, and is the reason we changed the intake manifold gaskets (based on a mechanic’s recommendation after a pressure test.) We think the leak is in a freeze plug inside the engine (that’s a whole other story).
I haven’t been able to find a manual gauge at Autozone, so I’m going to try elsewhere. But right now, it seems to run at about 90-110 pounds until it warms up, then drops to 65 pounds. My son’s concern is that it would drop to below 30 pounds while he is driving.


#7

Also, the idiot light doesn’t work for me. It’s always on and has been since we bought the car from my father-in-law.


#8

Interestingly, the oil pressure only drops after it has been driven for a while (45 miles or so), and he has to come to a stop. If he drives it continuously, it doesn’t seem to drop. Also, I’ve replaced the oil pressure censor a couple of times now with the same results.


#9

Did you ever hook up a mechanical oil pressure gauge as was advised many times?


#10

30 to 40 PSI at idle is normal, the specification is 60 PSI @1850 RPMs. 90 to 110 is rather high, I suspect you instrument cluster gauge is not as accurate or realistic as you are expecting.


#11

The problem might be with the oil pressure relief valve.

https://www.rockauto.com/en/moreinfo.php?pk=366864&cc=1371248&jsn=514&jsn=514

This oil pump repair kit includes the relief valve with the spring.

Tester


#12

fwiw, my early 70’s Ford truck’s oil pressure tends to start out with the engine cold around 60-70 psi, then drops to 35-40 psi as it warms up, at idle. It’s always done that since when the truck was new.


#13

That seems normal to me @GeorgeSanJose. Real oil pressure gauges aren’t usually found on cars or trucks but when a real gauge is installed cold pressure is usually 70+ and hot pressure 30+. Old British sports cars had mechanical gauges that often jumped to 90 cold even at idle but when hot 45+ cruising and 30+ idling.

For the past 20 years Ford has made their oil pressure gauge a dummy. The pressure sender is just an on off switch that turns on at about 10 psi and moves the needle to the midway point on the gauge.

I suspect that the OP’s car has a problem with the stepper motor gauge. They aren’t actually connected to a pressure sensor.


#14

Car seems to be holding pressure at this point. I changed the oil, plus swapped out the oil sending unit. Still fluctuates when it’s been running for 45 or 50 minutes, but it doesn’t appear to be plummeting as it had been. Still have a “vacuum miss” that I can’t seem to locate, which also started after we swapped out the upper and lower manifold gaskets (which apparently didn’t really need to be replaced.) I know my son is a bit frustrated. I’ve tried explaining that this is what happens with cars with 200k on the odometer, but sometimes 18-year-olds don’t like to hear that kind of news.