Oil leaks on Chevy LS engines

[BrendanC]

i work on a fleet of these and own one. rear cover gasket needs to be replaced along with the rear main. i’d reccomend replacing the oil pan gasket and oil cooler lines while you’re in there aswell.

ONLY use GM gaskets and seals, others will leak after a short amount of time. while you have the oil pan down, it’s a good idea to replace the oil pickup tube O-ring aswell as add a cheap-o amazon LS oil pump pickup girdle. it uses both bolt holes in the pump instead of one to help keep the pickup tube secure.

the hardest part of this job is removing and reinstalling the transmission but the rest of it is very easy with a bunch of 10mm headed bolts.

 

[tblt44]

Both my 2003 & 2006 5.3 leak from looks to be timing chain cover blowing back.
I originally thought rear main or oil pan

 

[redhat]

If the rear cover is off, it’s also worth replacing the oil galley barbell. Drill a hole into it and thread a Sheetrock screw in and pull it out. Another source of oil pressure issues.

 

[Snagglefoot]

This shot shows that the upper part of the bellhousing does not seem to have oil coming coming down it from the pressure sensor.

 

[clinebarger]

There's a plug on the end of the oil cooler block that's sealed with an O-ring that will harden & leak. Swap that along with the oil cooler to pan gasket. Clean it all up & recheck.
I use a A/C o-ring of the correct size for the plug

The Oil Pan gasket & Rear Cover gasket are both exposed to full oil pressure & will eventually leak. In the case of a Gen IV....So is the Valley Cover gasket

Mahle gaskets & seals work well on Gen III & IV LS engines. Fel-Pro is okay except for their Valve Cover gaskets.

 

[Snagglefoot]

There's a plug on the end of the oil cooler block that's sealed with an O-ring that will harden & leak. Swap that along with the oil cooler to pan gasket. Clean it all up & recheck.
I use a A/C o-ring of the correct size for the plug

The Oil Pan gasket & Rear Cover gasket are both exposed to full oil pressure & will eventually leak. In the case of a Gen IV....So is the Valley Cover gasket

Mahle gaskets & seals work well on Gen III & IV LS engines. Fel-Pro is okay except for their Valve Cover gaskets.

Might this be the plug on the oil cooler block?

 

[Snagglefoot]

I take it this is the inspection plate and it pops off with a screw driver.

 

[redhat]

I take it this is the inspection plate and it pops off with a screw driver.

View attachment 212998

You are correct. Just some tin tabs.

 

[ls1mike]

I have more photos loaded. This group focuses on the oil cooler block that is bolted to the block. There is definitely is one leak there.

View attachment 212947View attachment 212948View attachment 212949

That oil cooler block is common and will make a mess like that. It is an easy fix.

 

[Lawnman23]

Just an observation, I had a pesky leak from the back of my 5.7, most likely the rear main. I switched to Castol GTX High Mileage 10w-40 and the leak has resolved itself. Surprisingly I had ran other brand HM oils and none made a difference till I ran the Castrol.

With that many miles on your engine, its no surprise seals are getting hard and weepy.

 

[Snagglefoot]

That oil cooler block is common and will make a mess like that. It is an easy fix.

I take it it has no gasket from the factory and is metal to metal and that GM makes a gasket for it to fix the leak. Sound correct? Thanks.

 

[BrendanC]

I take it it has no gasket from the factory and is metal to metal and that GM makes a gasket for it to fix the leak. Sound correct? Thanks.

there is a gasket there.

 

[ls1mike]

I take it it has no gasket from the factory and is metal to metal and that GM makes a gasket for it to fix the leak. Sound correct? Thanks.

There is a gasket. I have one hanging on my wall. It was for my old truck when the time came.

 

[redhat]

There’s two styles of gasket applicable based upon your equipment. Make sure to get what you need. Top here is the gasket for when you have an oil cooler line block.

Then below here is when you have an oil cooler block off plate.

They’re usually pretty good gaskets. I think I saw a paper style before. I wouldn’t expect those to be any good so don’t seek them out.

 

[redhat]

While its fresh in my mind, BTR (Brian Tooley Racing) sells all the same GM Genuine gaskets on Summit Racing, almost same part numbers. From what I can tell from ordering a few, and from the appearances, numbers and packaging, they just resell GM. Usually a little bit cheaper too.

 

[clinebarger]

Might this be the plug on the oil cooler block?



View attachment 212996

Yes

 

[Snagglefoot]

I picked up a seal for my existing cooler line block. Made in Mexico. Canadian part number shown. Thanks for the help.

 

[Gasbuggy]

My LSA was leaking at the rear main by 40k

 

[Snagglefoot]

Yes

I replaced the oil cooler block gasket with a new GM one that looked identical. I’m still getting an oil droplet forming. Next time I take the truck out of service, I’ll undo the end the plug on the side of the block and change the O ring like you suggested. Photo is looking up, beside the new oil filter. Thanks.

 

[Snagglefoot]

I came across this 10 year old posting from the the Tahoe Yukon Forum where the person cut a chunk of 3/8 inch hex wrench to fit into the recessed end of the side plug in the oil cooler line block. By removing the plastic cover on the transmission he was able to get the chunk of hex wrench into the recess and use a crescent wrench to turn the plug out and change the O ring. Apparently a 9/16 O-ring fits. This is my current plan.