Lesabre oil leak

[jgunner]

I just bought a 1995 Lesabre with 73000 mi on it and I'm noticing smoke coming off the exhaust manifolds. I tightened the rocker covers but still can see smoke coming off the manifold. Anyone have any ideas what may be causing this?

[tman]

I had the same problem. I had to replace the intake manifold gaskets. It was a very time consuming job.

[edg]

Likely causes are leaky valve (rocker) cover gasket, cracked valve cover, cracked cylinder head, or leaky oil pan gasket. Less likely causes are intake manifold gasket, head gasket, or leaky oil filler tube. Are you sure it's oil? The transaxle and/or transaxle lines can put transmission fluid onto the exhaust manifold. Trans fluid has a different burning smell than oil.

[tman]

mine was leaking oil from the intake gaskets. I did change the rocker arm cover gaskets while I had the engine all tore up though.

[jgunner]

[quote=edg]Likely causes are leaky valve (rocker) cover gasket, cracked valve cover, cracked cylinder head, or leaky oil pan gasket. Less likely causes are intake manifold gasket, head gasket, or leaky oil filler tube. Are you sure it's oil? The transaxle and/or transaxle lines can put transmission fluid onto the exhaust manifold. Trans fluid has a different burning smell than oil.[/QUO

I'm sure it's oil. The rear cover bolts seemed looser than the front and tighting them eased the smoke and the smell coming from the back side exhaust manifold. The front bolts didn't need much tighting and I cant see where the oil might be leaking from. It seems unusual for the gaskets to fail with only 73000 mi on it. What do you think? How could I diagnose a cracked head? It's real tough to see behind the exhaust manifold

[edg]

If tightening the bolts eased the smoking some, your best course now is to replace the valve cover gaskets. After their original seal is broken, the gaskets won't stop leaks anymore. Make sure you thoroughly clean the old material, oil, etc. from both mounting surfaces and tighten the bolts to the correct torque spec using an alternating tightening pattern.

As to why they failed, it's hard to say. Someone may have removed the valve covers for one reason or another and instead of replacing the gaskets, reused the old ones. Alternatively, an overheated engine or excessive vibration could contribute.

Diagnosing a cylinder head issue is fairly easy. Check for radiator fluid (water / antifreeze) in the oil. Do a compression check.

[tman]

My service manual said not to use any sealer on the gaskets, and I've yet to have a leak. Bolts were tightened in sequence to 88 inch lbs. I believe. I'll copy the pattern for you later if I remember. If I forget, send me a PM, and I'll do it for you.

[joshey]

i think rtv works great i use it on all my gasket surfaces!

[tman]

yeah, its a black permatex right?

[joshey]

no, blue for acceptable surfaces,silver for high temp stuff

[Flatrater]

Originally Posted by tman2093

My service manual said not to use any sealer on the gaskets, and I've yet to have a leak. Bolts were tightened in sequence to 88 inch lbs. I believe. I'll copy the pattern for you later if I remember. If I forget, send me a PM, and I'll do it for you.

Valve cover gaskets are made of rubber that GM states do not use sealer on them!

[HannabilRox]

Yeah, rubber...cork...they all say they will seal...but I have found the ultimate that lasts a looooong time, is to:
1) Clean the gasket surfaces extremely well, scraping off all of the old gasket and sealer.
2) Use Gumout carb cleaner as a final cleanser on the gasket surfaces. This cleans leftover gasket sealer rather well.
3) Use Permatex Hi-heat silicon (I think its an orange color) and coat BOTH gasket surfaces.
4) Mount the part(s) and torque to specs.
5) (Very important) let set for a full 24 hours before running engine. Boy, what a sweet long lasting seal....plus it is a bit easier to remove the silicon sealer if you ever have to re-seal again down the road! I put a whole 225 CID Slant Six together with that method and never a drop of oil for years, even from that tough-to-seal slant six valve cover!

The Permatex #1 (black) & #2 (Brown) type sealers can be a REAL pain to clean off if you ever have to re-seal again.

Thought I would respond from my experiences.

[tman]

Originally Posted by Flatrater

Valve cover gaskets are made of rubber that GM states do not use sealer on them!

Thats right, and I didnt. I used tha black permatex I mentioned on the seals at the front and back of the block on the intake manifold gasket set. Exactly where my service manual said to do.

[Flatrater]

When you use sealer near the engine I will give you one word of warning! Any trace amount of sealant gets on the O2 sensor will ruin it!

[joshey]

the only way it would get to the o2 sensor would be a. to mount the o2 sensor with rtv or b.do something stupid. i use to fallow instructions till i realized who wrote them, people, and being people they all have there own way of doing things. i use rtv blue on everything but head gaskets and if you mike the head and shine it up like your suposta then you have no problem.