'02 Impala 3.4L: Intake Gasket Morass
Earlier this year (April), I purchased the Felpro intake manifold gasket set for my Impala from Autozone. I think it ran about $80. Haven’t installed it yet. Haven’t even cracket the seal on the box! Recently I discovered that there is yet another new OEM gasket set available from the dealer (#19169127) which replaces the old kit (#89017279). This new kit includes the 8 bolts which have the thread locker already on them and sells for $45 (here). Today I stopped by the dealer to take a look at these gaskets and place them side-by-side with the Felpros I have (since I had never seen the OEM gaskets at all). Much to my amazement, the EOM gaskets appear to be entirely made of thin, flimsy, molded plastic - except toward the ends where there are a couple of thumb-tack-sized dimples that appear to (maybe) be metallic. These gaskets bend and twist very easily in your hand - much like those cheap clothes hangers that kids clothing is sold on. The Felpros, on the other hand, are almost entirely made of metal. They look like they were fabricated by cutting openings out of a thin sheet of metal and then lining these openings with plastic! Even though I haven’t held them in my hand yet, looking through the plastic window on the box, they appear to be far more substantial because the inner metal web is fairly wide in places.
The question is: should I return the FelPro gaskets and purchase these new OEM gaskets? They’re cheap enough. Granted, I’d have to buy the valve cover gaskets separately at Autozone for $13/pair, and maybe some O-rings, but I’d be getting the new bolts (which look awfully flimsy too, by the way) and I’d be using the GM-approved gaskets. The problem is, the OEM gaskets look like junk to me. I thought the new gaskets were supposed to have more metal in them (like the FelPros do). Turns out they don’t have ANY! Maybe this is actually BETTER?? - to make the gasket more flexible? Maybe the rigidity of the FelPro might actually turn out to be a drawback?
It’s not the frame part of these gaskets that fail, it’s the silicone sealing beads that fails on these gaskets.
These silicone beads are what creates the seal between the intake manifold and the heads. Because the heads are cast iron and the intake manifold is made from aluminum, they expand and contract at different rates when the engine heats up and cools down. The different rates of expansion and contraction between the two causes these silicone beads to be rolled back and forth between the two surfaces. This continues until the silicone bead finally seperates from the gasket frame, and an intake manifold gasket leak developes.
So compare the silicone beads between the two. And use the gasket that has the thicker bead.
Tester
Metal corrodes due to the chemical dissimilarity between aluminum heads and a steel block or steel sleeved aluminum block. One of the main functions of antifreeze is to provide protection for these galvanic reactions. If GM says plastic gaskets work to their specs, I wouldn’t argue. Use what you like, but keep that antifreeze changed every year or two at most. There is no such thing as permanent antifreeze – it’s just permanent from season to season and that’s all.
Oh. I guess that makes sense. I’ll have to look more closely at both sets of gaskets. To me it just looked like thin, flimsy plastic - about the same size - on both of them.
Tetser:
When did they make a 3.4L with cast iron heads? I always thought the were aluminum.
~Michael
If you go with an intake gasket with less thickness, and therefore, less crush, it would be a good idea to take the intake manifold to an automotive machine shop to have the sealing surface lapped flat. This could keep the new gasket from leaking from uneven mating surfaces.
Well, after reading about the FelPro gaskets and realizing these are the latest and greatest design from FelPro, I feel a lot better about them now. It turns out there are different versions of FelPro gaskets still floating around parts stores. I bought my set at AutoZone earlier this year, but I stopped by an Advance parts store recently and discovered that, while they also sell the kit I bought (MS98003T), they sell the intake gaskets separately too. However, this set is a totally different gasket design: no metal, just very cheap and flimsy black plastic like the OEM gaskets, and more importantly - the sealing surface doesn’t look as thick as the surface on the kit gaskets.
SO - I would say if you are going to use the FelPro gaskets, use the ones with the metal frames found in the MS98003T (PermaDryPlus) kit. These are FelPro’s latest design. For the Impala, they only hit the market last year (the first version was sold in 2004)! You can also read about them on the Web - the chemical composition, and how FelPro stressed tested them with no failures. To me, they really DO appear to be the better gasket design.
If anybody out there has a compelling argument to the contrary, I’d love to hear it.