Oil Under Intake Manifold on Northstar

[Lawrence]

Hello all,

I have had an oil leak (94 STS) for some time now and assumed it was the typical NS oil pan/case half problem. Although I cleaned the area well and dye tested I still could not positively locate it. It seems to be coming from the rear of the engine at the rear main seal/oil pan area dripping onto the exaust and burning/smelling.

I have now noticed there is a considerable amount of oil laying under the intake manifold. In one place about an inch deep. I am hoping this is the same leak I have been looking for down at the oil pan.

Before I pull anything down I would like to ask what the source of this oil might be? Is there anything that could leak oil under the intake manifold other than the valve cover gasket? It does seem to be engine oil and not PS fluid.

Any help appreciated

Thank you,

Sincerely,
Lawrence

[Lawrence]

OK, I've done some searching. Sounds like a head gasket. Is there anything else it could be? Do i even need to pull the intake manifold to check for something else?

Thanks,
Lawrence

[Lawrence]

Well, I found it. It is indeed leaking through the rear head gasket right at #1 where the oil feed to the head is. The gasket looks good but the oil is just flowing over it. It would seem as if the head is loose. I have done compression and leak down tests which were good though. That cyl (#1) was within 5%. No oil in cyl.

I am curious. Is there a metal band around this oil passage in the head gasket or just the fiber? Sure seems to be a strange failure.

What to do to fix it? Is it possible I could re-torque the head bolts?

[zonie77]

Are you sure it isn't from the cam cover? I have heard of this happening (not on a N* though)
The threads in the block tend to strip on a N* with headgasket problems. You may have a problem retorquing the bolts. The bolts are a little different because they can only be torqued once and the procedure is torque to a spec, then turn an additional 60 deg. Makes it hard to retorque. You could see how it feels when you try tightening though.

Here's a something to look at, view of the block surface.

http://caddyinfo.netgetgoing.com/howto/nsrepair.htm

[Lawrence]

Yes, positive. I could see the oil just pouring over the gasket like a waterfall with the engine running. At least an inch wide. I could see it directly by looking down behind the PS pump. I cleaned the area with brake cleaner and started the motor, after about 30 seconds you can see the oil directly emerge from between the head and the gasket. No chance that it is running from anywhere else. Strange, runs like a champ.

Thanks for the pic. zonie77. I saw you had posted it somewhere earlier and after seeing the oil feed hole in that picture suspected I could see the area on the car at least at the rear head without removing anything and only the PS pump to see the same area on the front head. I ran out to look and sure enough........ The picture helped me zero in on the leak, not being familiar with the engine.

The gasket appears intact. It really looks as though the oil is squeezing out right between the gasket and the head, again at least an inch wide. You would sure think that if the head were that loose it would have blown the combustion seal.

Exactly what usally happens to the head bolts. Do they stretch, rotate out, block threads deteriorate, or does the gasket shrink from under them?

I have to say I am not pleased with the Cadillac on this issue. I know you hear all about every products perceived misgivings all over the internet in their associated forums. Every one who has problems with the products collect there, right. I have been reading alot about the NS problems too, and trying to keep it real and in perspective. I also understand failure rates and all but when you see something like this first hand it makes you wonder. And understand why so many owners are upset. There seems to be no reason this should have happened. I would wager if I could get at the area I could slide a feeler gage between the gasket and the head. It really wasn't even necessary to pass the pressurized line through the head gasket. Pity.

Any other thoughts to correct this, please post them.

Thanks again,

BTW, It also appears that there in no combustion force behind this leak. It flows out nice and steady, apparently only from the oil system pressure.

[Lawrence]

I am starting a new thread;

Head bolt retorque method recommendation needed;
http://www.cadillacforums.com/forums...ead.php?t=8127 (Head bolt retorque method recommendation needed)

[zonie77]

That's what I was getting at in the prev post, there is no official one. There are charts, based on bolt size, of recommended torque though. They are in most Chilton type manuals.