Ive got low oil pressure on my 2006 supercharged 3.8L 153K mi. I put a mechanical oil pressure gauge on it; when I start it up cold it idles with 50+ oil psi, but when it warms up it idles at 5 psi and has 25 psi at 2500 rpm. I changed oil and put mobil 1 synthetic 15w-50 in and it didn't make any difference. I cut the old oil filter apart and there are no shavings so I don't think the bearings are going out of it, plus the motor sounds fine; no bad noises. I took the oil filter housing off to inspect the spring and plunger and they look ok and the plunger moves freely in the bore. Has anyone else experienced similar symptoms and found a solution?
Low oil pressure
- Thread starter mrt23
- Start date
QUICKSILVER462
New member
Check for sludge on the bottom of the oil pan. Sludge on the bottom of the oil pan car restrict oil flow and cause low oil pressure, especially after the engine has run for a few minutes (warming up). At first start up, the sludge has moved away from the oil pickup tube/screen, after running the sludge starts to cover the pickup tube restricting oil and reducing oil pressure.
BillBoost37
New member
Are you sure your mechanical gauge is accurate?
BillBoost37
New member
ps.. if the car runs great, and you put the gauge on, just to know what it had for pressure.......take that gauge off and throw it away.
You were fine before you hooked it up, likely you'll be totally fine w/o it.
You were fine before you hooked it up, likely you'll be totally fine w/o it.
I would think at 5psi that motor would be knocking pretty well. Usually when the low oil pressure light comes on it means "change engine". It's possible that the pickup tube gets clogged up, but then you would usually hear noisy lifters. Any way you can get an electrical pressure gauge and check it?
No knocking, no lifter noises, no shavings in the filter, I don't believe my guage to be faulty because the display on the dash indicates low pressure too. I replaced the oil pressure switch thinking that was probably my trouble was, but the warning still popped up, so I added the gauge to verify low presure and it does
BillBoost37
New member
A little heads up for you.. dropping the pan won't allow you to put in a new pump. This motor isn't quite identical (less 2 cylinders) to a 350. The pump is in the timing cover and typically does not have any issues.
I've never been into a 3.8L, thanks for the heads up! The oil pump is about the last logical thing for me suspect, I think its a little odd that it has such good pressure when you start it up, Ide expect a fair amount of drop once its warmed up, but 60 to 5 psi seems a little extreme. I think I will still drop the pan and look at the sump screen. Do you know if I can get the pan off without raising the engine or removing the subframe? Thanks for the help.
mrt23, Good detective work on the oil pressure. I'm working on a L67 that spun a rod bearing. It has worn camshaft bearings, may have caused a oil starvation and now the engine is in my shop. Specifications on the oil pressure is 60psi @ 1850 rpm. If the oil pan, pickup is clean. Another area is the oil pressure relief valve. It's located inside the timing cover and can be accessed by removing the oil filter adapter. I've seen debris like gasket parts, RTV or carbon chunks jamming the valve open, bypassing the oil, lowering oil pressure. FYI - having a new gasket ready will save time. I've also had the timing cover gasket fail - allowing high pressure oil to bleed in the the timing chain area.
I did take the oil filter adaptor off yesterday and unfortunatly the spring and plunger look fine and it moves free in the bore, I also notice there is a little spring loaded relief valve right where the filter screws on, but it seems to be ok too, strong enough to hold 60 psi before the oil warms up. I've got an oil leak somewhere on the front of that motor, I figured its still dripping off the subframe from a leaking oil pressure switch, but I've cleaned the whole front and subframe so I can see if its still leaking, you might be onto something with the timing cover gasket, I will look into that as well, thanks.
I've got oil dripping off the plastic crankshaft position sensor shroud right behind the dampner, about one drop every 5 seconds when the engine is running. I doubt that it is the front main seal around the dampner because I have the right side of the car jacked up plus the crankcase shouldn't be under pressure to force it out. So, I'm thinking that Flashman might be right about the timing chain gasket. The attached picture is NOT my engine, its a pic I found on the net, I think its and older LeSabre, but my question is are those the high pressure oil galleys right below the water jacket torwards the rear of the car you are talking about I assume? Where exactly is the oil pump? Also, the dampner has a broken puller bolt in one of the deep-down-inside-there holes, is there any alternate ways of pulling the dampner?
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tomtom123
New member
Image is rotated to the left.
This was the bad seal. It was just a little rip in the rubber that was leaking.
This is what I saw when the seal behind my balancer was leaking. And it only leaked when the car was running. Just a drip at a time but still rather fast. Easy fix though.
Idk how to get the balancer off without the 3 studs though =/
Mrt.23. The high pressure oil feed comes out of the timing cover and enters the block just below the coolant passage. If you pull the timing cover, look for the pressure release nozzle on the inside of the cover,you had the spring and piston. Inspect for failed gasket or cracked timing cover. The oil galley feeds the crankshaft first, camshaft, lifter bores on one side of the block. Is channeled to the other side of the block via rear main seal housing and feeds the other lifter bores. Also a galley also feeds the rear balance shaft bearing. Hopefully the problem is in the timing cover area. Another thought, the integrity of the oil pump feed to the pump. blockage or air
entering the inlet passage to the pump will lower oil pressure.
entering the inlet passage to the pump will lower oil pressure.