The LIM gasket on the 3.4L was replaced 40k miles ago due to leaking coolant. I've notice it has been leaking oil past the RTV sealant of the LIM gasket at the front and back of the engine. So, I'd say the guy at the dealer must not of cleaned it up all the way, or didn't seal it up right. Though everything else is dry, and I haven't noticed any coolant loss. And no oil milk shake.

I was thinking of replacing the LIM to fix this, but not really interested in doing it either. Just wondering if I could get by like it is as long as I keep an eye on the oil level? Or could there be something going on inside that could be causing damage?

I'm assuming no oil and coolant are mixing with this type of leak? As I've seen pics of coolant passages plugged up with the LIM removed due to coolant and oil mixing together.

 

Check around your heads and the valve covers for oil leaks

 

Make sure it's first not something like a leaking water pump. Best way to check, get a radiator pressure tester. If it drops pressure, inspect around the engine as it does.

That does not sound like things were done right. LIM gaskets on 3100 and 3400 engines last about 80K-120K in my experience (that's the crappy nylon ones).

If you are seeing coolant coming out the lower mating surface of the LIM, it suggests a couple of things:
1 - The mating surfaces for the LIM gaskets were not properly cleaned of old gasket and debris (or have some damage like a nick in the surface) that is preventing the seal for the coolant passages to do there jobs.
2 - The gaskets blew out again.

Using a pressure tester and inspecting should help determine what's going on. Get it fixed before it becomes a problem (and next time, use the aluminum LIM gaskets).

 

Already did and everything else is dry. The oil is leaking where the RTV is at inbetween the heads at the front and rear of the engine.

My guess is the guy didn't clean up all the oil film before laying down the RTV.

This is a pic of the RTV where the oil is leaking at:





I did clean the oil up before and added a tracer in the oil to check with a UV to make sure it was oil that was leaking.

 

It's not coolant. It's OIL leaking past the RTV. I've already cleaned it up and added a UV tracer to the oil to further confirm it's oil and where it's leaking at.

If it was coolant, I'd go ahead and change it. But since it appears to be oil just leaking past the RTV, I was wondering if it's something that can wait as long as the oil level is maintained? I'd assume the gasket is still good and the coolant/oil isn't mixing.

I've had other older GM V8 cars where oil leaked out the RTV from the back of the engine at the intake manifold. Seems to be a common problem on those engines.

 

Sorry, I mis-read your original post.

Sounds like you are on target, may be the valley surfaces were not properly cleaned. I also know that you can get the finest amount of oil seepage where the LIM, Head and Valve covers meet and it's just enough to show as a film down the head (it never looks wet, but you can tell it was there). But you never loose oil. I think that is just how the 3100/3400 is having that weird meet point where all three hit.

If it is leaking from the RTV, when ytou have proper temps, you might be able to clean it up a little and goop some on to "touch up".

 

That wouldn't work as I did clean up all the oil on the passenger side, but the RTV sticking out still had oil film on it. Plus on the driver side, too much stuff to be able to get to it without tearing into it.

I've read of some putting a dab of RTV in the corners under the LIM gasket to help seal that off. Is that what you guys normally do? I did read somewhere it say NOT to do that as it could affect the LIM gasket from sealing to the head.

Here's a pic of a guy putting a dab of RTV in the corners before laying the LIM gasket down:





If I redid the gasket, I'd think about using Permatex The Right Stuff. As I know alot of guys use that on the china walls of those older GM V8 engines to help prevent a leak. But I believe that stuff is supposed to be harder to clean up at a later date compared to the regular RTV stuff that is used. And some say it's a pain to remove the manifold as I guess The Right Stuff really bonds well.

But I guess my original question is if it is safe how it is leaking right now as long as I maintain oil level? As I'm not familure with these engines and would'nt want the coolant passeges to get pluged up from the pics I've seen. But I haven't noticed a coolant loss, and I haven't seen any evidence of coolant in the oil. But I haven't put alot of miles on it either since I got it.

 

As for a dab of RTV in the corners, that's how I've done the gaskets on my cars, then seat the gasket and lay a bead of RTV along the valley and finally seat the LIM. My experience, it makes for a good seal.

As for safe to drive, by your description, sounds like it should be no problem. It does not sound like you are flooding out lots of oil. But do make sure that the oil level is good. The only side effect of driving will be additional oil crud to clean up around the engine, but no big deal. Heck there are probably tons of people running these engines right now not even aware there is an issue (when they are on the verge of one).

OH as for using a different product, I've always used the tube of RTV that FelPro includes with the gasket kit. Never had an issue and never ran short, they give you plenty of that stuff.

 

I also did the dabs in the corners before laying the gasket down. Permatex rtv is what I use... Ultra black works good

 

What are you using to clean up the mounting surfaces to prep for the RTV?

And does the LIM have mounting pins or something to make setting it down pretty fool proof?

The main thing I was worried about was torquing the rocker arms. As I just have a cheapo torque wrench, so not sure how accurate it is. And would have to get that degree tool. Though, they do have that tool that lets you remove the push rods without having to unbolt the rocker arms. So you don't have to torque anything down. Though since it was done before at the dealer, then I'd have to assume they torqued the bolts down properly. As I do hear a loud snap sound every once in a while that sounds like it comes from the front valve cover area.