wm_sorg

Hi All,

I noticed a small film of oil on a metal tab below the left valve cover. It valve cover leaking a common issue with the LT5. Ot is it my exhaust manifold bolts? There are no spote on the floor and the oil pan looks dry.

91mongoose

Since the "valve covers" on an LT5 actually for part of the bearing surface for the cams they don't have a gasket. They are sealed with a glue like substance (can't remember the name) from the factory (and it you do a rebuild, etc). As such I find it highly unlikely that the cam cover would leak since the glue won't wear out and the covers are torqued tightly to hold the cams in place.

That being said I'm not sure where it would have come from - the exhaust manifold bolts can't leak (no oil there). Maybe the exhaust manifold stud?

wm_sorg

That is what I am confused about. I read a few posts where it mention oil leaking from the maifold bolts (studs?) where they have to be removed and sealed something to prevent leakege. Where are the studs located? How are they different from manifold bolts?

DDSLT5

You'll have to dig into past threads - I believe it is the middle one or two studs on earlier model LT5s (90-92) that passed through an oil gallery - therefore, when they start to leak (obvious as the oil burns off of the manifold), you must remove them, place sealant (loctite?), and reinstall, and bingo, oil leak solved. I believe this was discussed on the net as well. :seeya

wm_sorg

So this problem was solved for 93-95 engines? I will check the net as well.

Jeffvette

I'm with Dwight. Check the studs, have fun doing it though :D

Also the "glue" for the cam covers is anerobic sealant. It's pink, it's expensive and it is a major PITA to get out of the tube.

DDSLT5

They (read: Graham Behan who was in charge of the upgrades for the second generation of LT5s) changed this on the second gen LT5 - no longer had any studs passing through oil galleries due to this problem. As it gets more and more loose, you'll see a nice puddle on the floor overnight, and also a cloud of smoke on start up.

:seeya

90 Corvette ZR-1

I am having this problem right now. I think its the middle stud. I've read that it is not that hard to fix. Remove the stud RTV the hell out of it, reinstal and let sit for 24 hrs.

A26B

Most probably the center exhaust manifold stud like everyone else said, but there is one other less likely but not unknown possibility, cam cover dowdy washer leaking. Go for the stud first, wipe it down very clean afterwards and then check to see. If it's a dowdy washer, it will be coming from up higher than the cam cover/head mating line.

wm_sorg

I will monoitor the stud and do this procedure if needed. Looks like it's impossible to get to. Not that much space in there at all.

90 Corvette ZR-1

From the ZR1.net

20. TITLE - Oil leak from header studs.
YEAR(S) - All

PROBLEM - It has been well documented that the LT5 commonly leaks oil out of the header studs side, and leaks down on the cat. If it sits around a couple of weeks, it would smoke badly after about 5 minutes of warm up. On each header side is a stud located in the middle of the header, where it mates to the manifold. The stud is about a 1 1/4" long and has a nut welded on. The stud screws into the block and into one of the oil galleries. With all of the heat generated here, the stud will fail to seal and an oil leak is the result.

CORRECTION - To fix the problem, use the following procedure.
1. Remove the front tire from the side to be fixed.
2. Remove the rear inner wheel well. It has an assortment of Torx and hex head bolts.
3. You will now be able to look at the headers and see the stud, situated between the first 2 and last 2 cylinders.
4. Use a 15mm socket to remove the stud. The nut is welded on to the stud.
5. Clean up the stud, and apply a liberal amount of high temp Red RTV to the threads.
6. Very carefully thread the stud back into the manifold. This is the hardest part, as it is very close quarters. Don't drop the stud, or it will fall into the deep crevices of the exhaust tubes.
7. Let the RTV set up overnight, and enjoy a leak free LT5.
8. As long as you have the wheel well out, you might as well clean the air bag crash sensor, located on the frame rail. The right side one gets a lot of AC runoff, which corrodes the grounding. Disconnect the battery ground before removing the sensor. The sensor has 2 different bolts securing it. (13mm and 10mm I think). Once removed, you can clean up the surface and apply some dielectric grease to the surface to keep the water out. The main grounding comes from the bolts, so make sure they're clean.

SERVICE BULLETIN/RECALL - None

RedZR

Do not put too much RTV on it- remember it's naer a gallery and the last thing you want is a piece of that sealant breaking off and clogging a passage.

Dan