5.3 oil pressure issues (HELP)

[93 Krawler]

Earlier this year I pulled the engine out of our 05 Envoy Denali because of some major knocking. Found the rod bearing gone, so time for a rebuild. LH6 Alum 5.3

Took the engine to Performance Engineering in Hamilton for the machine work. He got the rolling assembly, and that's how I got it back. So I put the heads, oil pump, timing cover, oil pan on. He did all the important stuff.
So the engine has a new crank, rings, and cam, plus all the rest of the usual wear items. I also removed the DOD crap.
Almost 3000 miles on the rebuild and my wife calls and says the oil light came on. The oil pressure on the dash was 41 cold and 35 warm at idle for 3000 miles. Now showing 22 at 3k rpms and 0 at idle warm.

I first thought the sensor was bad so i replaced it. No change.

Decided to pull the pan thinking pickup o ring or something in the pan. Checked all and replaced the o ring for kicks. No change.

Bought a mechanical gauge to make sure the pcm wasn't messing with me. Nope...

Next was the oil pump relief valve. Took it out and made sure it wasn't sticking. No change.

Next off comes the front cover to replace the cam retainer plate and the oil pump while it was open, again, just to be sure. All this was new already. and still no change.

Last was over filling the oil and raising up the rear end to see if it would change. Nope

Car runs great and makes no noise. I did notice and 10 psi difference in pressures between checking at the oil cooler port at the oil pan and the OE gauge location at the back of the intake. It was lower at the factory location on the intake.

So what would make it lose pressure besides the cam retainer plate, oil pump, and pickup o ring?

[93 Krawler]

At idle semi warm. Taken at the intake port.


At 2000 rpms



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[93 Krawler]

I even pressure checked the oil pan to see if it was tight.



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[blazerbrad]

I'll shoot a text to a long-time GM mechanic I know and ask him if he knows of any common issues that could be related.

[bbtank45]

What is the specified oil pressure range?

Doing some research. When you did the DOD delete, did you block off the towers in the lifter galley?

[93 Krawler]

Originally Posted by bbtank45

What is the specified oil pressure range?

Doing some research. When you did the DOD delete, did you block off the towers in the lifter galley?

The towers were tapped and plugs were installed. The new valley cover has o rings that sealed them as well. I also plugged the extra bypass on the oil filter housing that bled off the extra pressure when the lifters were not in use.

Called the shop that did the work and he said it sounds like one of the cam bearings walked. That leaves the oil galley wide open and reduces pressure at the top of the block.
Looks like the engine is coming back out.

[93 Krawler]

Back to the shop it goes. Am I out of line in thinking since he built the short block, that he should take care of this for free? If the bearing walked, then the tolerances were off. I already wasted $300 thinking it was something i did.

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[Runoveru2]

This is their baby as far as I'm concerned,
It would be bad buisness to say this is on you.

[93 Krawler]

Got a call from the shop today. He said the #4 & 5 cam bearing walked out enough to leave the oil port open. He is going to make custom bearings to fit this time. Looks like he's taking care of it like he should.

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[JeffK5]

Originally Posted by 93 Krawler

Got a call from the shop today. He said the #4 & 5 cam bearing walked out enough to leave the oil port open. He is going to make custom bearings to fit this time. Looks like he's taking care of it like he should.

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So he machined the cam bores oversized when originally did the block and your already running a Durabond +.020 OD cam bearing?

[93 Krawler]

Originally Posted by JeffK5

So he machined the cam bores oversized when originally did the block and your already running a Durabond +.020 OD cam bearing?

No, there wasn't a need to machine the cam bores. On the aluminum blocks, the bearings need to be tighter than iron blocks from what I read online. Engine builders say they should've been pinned from the factory. Since he has to take the whole engine apart again, sure hope he inspects the rod and main bearings for wear.

[93 Krawler]

Got the engine back after 6 weeks. Put it in and this is what happened. Still no oil pressure because its running out the bellhousing somewhere. I am beyond pissed. Attachment 10056

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[93 Krawler]

Pulled the trans out to see why it was leaking, and found the rear seal was damaged. I don't think the rear seal leaking would give me zero oil pressure. So now the question is, why is there pressure leaking in to the rear cover.


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[jeepmanjeff]

Wow! Gonna call him tomorrow and throw a gasket?


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[93 Krawler]

Got it all back together finally. Replaced the seal and no more leak. The oil pressure sending unit connector was loose, so that's why no oil pressure. All.good now.

So it is advised that no one uses Performance Engineering in Hamilton. First time took 2 months to get it rebuilt, only to walk 2 bearings 3000 miles later. Second time took 6 weeks to get back only to find a mangled rear main seal. This is why i do my own work.

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