GM LIM gasket: Two more questions

[rationull]

Yet another post from me on my LIM gasket replacement job! Two questions in this post:

I picked up the new gaskets today and was looking at them side by side with the new ones to try and find the fatal flaw in the originals. My interest in this is both based on simple curiosity, and the fact that if the original gaskets *don't* have a leak, I'm on a long and somewhat painful wild goose chase.

I can spot an obvious flaw in the gaskets I removed, but it's hard for me to be sure this hole (on the right side of the rectangular coolant port) isn't damage from me tweaking the manifold around while removing it:

Does this look like a typical sign of failure? If not, what should I be looking for?



Second question: I was very pleased to learn that the FelPro gasket set comes with rubber strips to use to seal the front and rear where the intake seals against the block. But when I was in line to buy the gasket, the guy behind me apparently noticed what I was buying and told me not to use the rubber pieces, instead to use silicone liquid gasket. I very much appreciate all the help and first hand advice I've gotten on BITOG lately, and my question here is in your experience are these rubber pieces worthless? Seems like they'd be easier to install given they won't really smear around...

 

[Colt45ws]

First: Yes, that is a failure.
Second: Ive used those before, but you still have to RTV in the gap between the LIM and the stip, or it wont seal. That was likely his issue. 6 in one, half a dozen the other.

 

[JosephHarmon]

I have to believe the Dexcool Deteriorates this gasket over time. I would say any time after 75,000mi or 8 years. This Northstar coolant port gaskets hadn't blown yet but it was coming apart. The opposite gasket totally failed at 102,000mi.

 

[InvalidUserID]

Nothing to add other than yes, the Fel-Pro gaskets are pretty sturdy. I replaced my plastic GM ones with the metal Fel-Pro ones, feel better about my LIM gaskets now.

 

[The_Eric]

Originally Posted By: JosephHarmon
I have to believe the Dexcool Deteriorates this gasket over time. I would say any time after 75,000mi or 8 years. This Northstar coolant port gaskets hadn't blown yet but it was coming apart. The opposite gasket totally failed at 102,000mi.

Believe me, it's not just limited to Dex Cool.

 

[SteveSRT8]

^^^^you bet. And the good thing about Fel Pro is they are updated regularly to solve these problems.

Do it right and no more problems.

Note this is not a Dex issue but simply a bad gasket construction. Hence the updates.

 

[Trav]

From the picture its hard to say if this is a fail or not that happened during removal, the rest of the seal looks pretty good. If there are no marks around the seal material on the metal then sure that looks like a fail.
Usually when they fail the whole seal is looking pretty shabby but i have seen them fail in just one spot often enough.
Hope for the best, at least you know the LIM is sealed properly and that's a good thing to be able to eliminate from further diagnosis later if you need to do any.
Quote:
told me not to use the rubber pieces

Use them by all means, they provide a much more reliable seal then just RTV on the whole area. You do need to put a little RTV on the mating areas of the LIM gasket.
These are less likely to a leak for the reason you stated.
Most RTV failures are due to poor surface prep and voids created during installation, the latter being easily done when installing a large part like this that has a habit of shifting a little during install.

+1 on swapping the FPR out now, good call.

Edit: Yes that's almost certainly a fail. I the picture looks clearer with reading glasses.lol

 

[rationull]

Good. I wanted to use the rubber pieces!

So, RTV where the gasket meets the rubber strip (I assume this is what you meant too by "mating surface" Trav?) Seems like an application for Permatex Red, maybe. I will have to go pick some up and hopefully have time to clean everything up tomorrow and get the gasket set and the intake torqued down.

 

[Trav]

Quote:
where the gasket meets the rubber strip

Yes sorry if i wasn't very clear. Permatatex red is a good choice.

 

[rationull]

Cleanup is a bit more of a bear than I expected but I'm making good progress, and now taking a break from the carb cleaner fumes. At least I *think* the progress is good. I was hoping to get this thing spotless, but either I need to do some more scrubbing or 168k miles and 13 years if gasket contact just leaves some discoloration. Pics:

Before:

Now:

In addition to the mild discoloration around the intake ports, theres' some pitting around the coolant ports:

Hopefully that's not going to be problem but OTOH I'm not sure what I'd do about it if it were.

 

[yonyon]

You could fill up the pitts with JB Weld. Make it nice and smooth with a razor blade and if it isn't as smooth as you'd like hit it with some Scotch Brite or the finest sandpaper you have. I think the gasket material is soft enough that that little bit of erosion you have won't cause you any real trouble as it is.

 

[rationull]

Originally Posted By: Trav
Permatatex red is a good choice.


Actually I think I'm going to use some HondaBond high-temp I have left over from a previous car, after looking into it. The box for Permatex Ultra Gray mentions it's good for manifold ends, and HondaBond is basically the same stuff IIRC.

 

[edwardh1]

what was gm using before they started using the gaskets that fail, and why didthey make a change to the bad product?

 

[rationull]

Oh yeah, one more thing. I assume I should use some threadlocker on the manifold bolts -- any specific recommendations?

 

[rationull]

Looked in the book, and it recommends a specific part number of GM thread *sealant* as opposed to a thread locker. So now my plan is to use the Hondabond silicone for the end piece mating surfaces, and probably Permatex High Temp Thread Sealant for the bolts.

 

[wtd]

Yep, that is where the gasket was starting to fail. I saw that same thing on the gaskets from my 98 5.7L vortec. I've had mine replaced three times. Bad gasket design. The newest versions are metal instead of plastic. Unfortunately I don't have the latest version in mine so I'm sure mine will eventually have to be replaced again.

Wayne

 

[rationull]

The replacement Fel-Pro I got seems to be plastic, not metal. A google search for "95826 felpro" turns out plenty of pics, but it's black. Maybe it's metal cored or something though, I don't know. It probably varies per engine.

How long ago did you have to get yours replaced?

 

[Merkava_4]

Originally Posted By: rationull
Oh yeah, one more thing. I assume I should use some threadlocker on the manifold bolts -- any specific recommendations?


I use Permatex 2B. It's not a thread locker, but it's the only thing I've found that will prevent
the engine oil from spiraling up the bolt threads. I have a 2000 Buick LeSabre with the 3800.

 

[00firebird]

This might not be your exact engine but everything in the videos is accurate for what I've read on the internet.
http://www.autorepairinstructions.com/?p=37
Most people use threadlocker blue (its like $6). I didn't use threadlocker on mine because I didn't want to have to shear the bolts off if I had to remove the lower intake again. Make sure the torque spec is done properly.

Your other question about the RTV, use the rubber things and then put RTV on them where they touch the gaskets. In this video skip to around 5:50.
http://www.youtube.com/watch?v=eJuAAgWNzF0

Also, if you don't have the aluminum gaskets I would return them and get the correct ones. Felpro was the original supplier for the plastic [censored] ones. GM made the aluminum ones, and then felpro made a revised metal set shortly after. You will have to do some hunting around for part numbers.
rockauto.com has a pretty detailed catalog, you might find the info on there useful.

 

[Trav]

Great info on the aluminum frame gaskets! I had just gotten the LIM on a 3800 the same morning i read they had them for the 3800 in dealers. Got new aluminum gaskets and removed LIM, it well worth the extra trouble.
If they are available for this engine i would use them.