When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I have an LS1 with a 4L60E transmission. I recently rebuilt the engine. Ever since then I have been having problems with the oil pressure. When I first started it after the rebuild, it had 0 oil pressure. So I primed the oil pump via the port on the side of the block. The oil pressure came back, around 20~25 psi when idling and up to 50 psi when accelerating. I thought that had fixed the problem.
Recently I was away for a month on holiday. The car sat idle for that time. After I got back, I drove it a couple of times on short drives. The oil pressure seemed ok (around 25psi). Yesterday, it went back to 0 again unexpectedly. So I primed the oil pump again and it came back to 25psi at idle.
Today, I started the car and drove it around the block. The oil pressure seemed ok. But in the afternoon, I started it again, and I could here a 'clanging' noise coming from the engine. I cheked the oil pressure, and it was at 0 (in fact the needle on the oil pressure gauge was actually below the 0 mark (negative)). I know its not a problem with the pressure gauge as I verified the reading with what was being reported by the PCM.
Can someone explain what's going on, as I'm at a loss. Is it a faulty oil pump, or an air lock in the oil system or something else? I'm afraid to start the engine again as I'm worried it will cause some damage with no oil pressure.
Rebuild involved the following:
- heads reconditioned inc. valve reseating
- cylinders bored 10 thou
- new pistons, rings, double row timing chain, main bearings, cam bearings
- new high flow water pump
- new lifters, pushrods, oil filter, gaskets, etc
- oil pan and pickup are near new. I'm using a rear drop oil pan which is fairly deep a the rear.
In terms of break in procedure, I am using Penrite running in oil and a procedure based on forum recommendations.
My guess would be the o-ring where the oil pick up tube connects to the oil pump wasn't seated properly. Sounds like you may have damaged the engine
I agree on the O-ring possibly being damaged. Jury is out on engine damage, although "clanging" is both not a good sign, and one that also needs a clearer definition.....
In your situation, I honestly believe you have an air leak/O-ring problem. Otherwise you wouldnt be able to reprime the oil pump, and have it work OK. As much as you hate to do it, pull the balancer and timing cover, and make sure you have the correct color O-ring, and that it isnt installed incorrectly/cut/whatever. I really hope you havent damaged the internals. I would also get a new, aftermarket oil sender. Best of luck......
OK, so what color o-ring should I have? (its a 1999 LS1). Also, where could I be getting an air leak?
I was intending to replace the oil pan at some stage as my mechanic mentioned the one I have on there doesn't have a lot of ground clearance. Maybe time to bite the bullet and do it now......
Also, when I reprimed the oil pump, I removed the oil pressure sender and made sure oil was coming out the sender hole. However, I didn't check for oil coming out the top of the pushrods. (I assumed once the pump was primed and pumping , it would push oil up the pushrods fairly quickly). Is this an incorrect assumption?
OK, so what color o-ring should I have? (its a 1999 LS1). Also, where could I be getting an air leak?
I was intending to replace the oil pan at some stage as my mechanic mentioned the one I have on there doesn't have a lot of ground clearance. Maybe time to bite the bullet and do it now......
Think of a crack in a straw. If the O-ring has issues, or is the wrong one, it will act like a cracked straw. Youll have air getting in the "crack," and that is probably why your pump is losing its prime. The LS oil pumps are above the oil level, unlike the Gen1 SBC, where the oil pump is below the oil level, i.e., submerged. Also, I see your list of overhauled items, and see a lot of things. But no new oil pump?
Hmmm......just watched a youtube video on the LS1 oil system. They mentioned a steel welch plug that should be inserted into a hole in the block next to the oil pump. See photo below:
Welch Plug LS1 Block
I can't recall ever seeing this or inserting it. Could it be the cause of my problem with failing oil pressure? I would expect if I didn't have the plug in place I would never get any oil pressure?
Hmmm......just watched a youtube video on the LS1 oil system. They mentioned a steel welch plug that should be inserted into a hole in the block next to the oil pump. See photo below:
Welch Plug LS1 Block
I can't recall ever seeing this or inserting it. Could it be the cause of my problem with failing oil pressure? I would expect if I didn't have the plug in place I would never get any oil pressure?
If you didn't take it out, then it should be there. Unless the shop didn't put it back in there. That plug gets covered by the front main cover so I would think you would still get some pressure or it would all over the place. You can see it in the beginning of the video. The engine is upside down.
It could be the shop took it out when they bored out the cylinders. (they removed the dumb bell and all the screw in plugs as well). I do get pressure after I prime the pump but it will start to decay and then abruptly reduce to 0. So the cover does indeed hold the pressure, but not for very long. Also, I think from memory there is a path from the timing cover down to the oil pan, so if that plug is not there the oil will flow out and then flow down into the pan. Since the oil path has been greatly expanded, the pump wont be able to keep the pressure up, and eventually start to cavitate (pump air) so the pressure will drop to 0.
Spoke to the mechanic at the engine shop today. He stated that they didn't remove the welch plug at the front of the block. He is of the opinion (as is stockA4 and grinder11) that's its the o-ring on the pickup that's the problem. So looks like the oil pan is coming off again! If that's not the problem, he suggested pulling the timing cover and seeing what I can see.
IMHO, one of the few, and biggest mistakes GM made on these engines is designing different size O-rings and pickup tube diameters. They should've ALL been the same. That said, it is impossible for me to know which O-ring your combo needs. My OEM C5 batwing pan with stock OEM pickup tube, and Melling 10296 pump, takes a blue O-ring. If you have a stock OEM pickup tube, correct for your model year car, and the OEM pump, there should be an OEM part# at the GM dealer. When installing the O-ring, use a liberal amount of vasoline. Best of luck.......
There's a pressure regulating "piston" in a sleeve inside the oil pump. I had grit in my oil that caused it to stick open before, which causes low/missing oil pressure. Check that while you're checking your oil pump.
There's a pressure regulating "piston" in a sleeve inside the oil pump. I had grit in my oil that caused it to stick open before, which causes low/missing oil pressure. Check that while you're checking your oil pump.
That "piston" is commonly known as the oil pump relief valve. Yes, it can stick. But its not a common problem unless your oil is full of junk. OP, check this for proper operation, which would be sliding feely in its bore. It wont hurt to check it, but I seriously doubt that is the issue. Because if it sticks, OP wouldnt see a difference in pressure when repriming the pump....
Dropped the pan today. Removed the pickup - couldn't see any obvious issues. It has a blue o-ring and I had smeared it with some red RTV. After I removed the bolt holding it in, I had to 'wobble' it from side to side to get it out - the fit seemed tight. Can't imagine that it would leak.
Next I'm going to remove the timing cover. Got the balancer off (as expected the bolt was a pain to get out). Will update tomorrow.......
You dont need any sealer on the O-ring, IF it's the correct O-ring. Just use a small amount of vasoline, in the pump pickup bore, and around the O-ring.
12-09-2023, 04:36 AM
Help! No oil pressure! 
