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Intake manifold reseal

What is causing the need for all our vehicles to need a “reseal intake manifold”? '96 Mercury Mystique has been completed. '96 Buick REgal SE needs new seals or face disaster. '90 Jeep Grand Wagoneer now is recommended for this service along with '07 Buick LaSabre.

Hopefully the person “resealing” them is doing so by replacing the gaskets, rather than some other measure. Many of the cases could very well be attributed to age. The GM examples given could be attributed to the use of Dex-Cool coolant, which is damaging to many plastics over time, including the plastics GM uses in their intake manifold gaskets.

I dont know why exactly you are suffering a rash of intake gasket failures. While it does happen to vehicles all the time…there is no real specific cause for it…just age and gasket shrinkage I suppose.

When I install my intake gaskets I coat each sealing surface with an EXTREMELY thin coat of silicon gasket maker…I have done this for over 20 years and NONE of my gaskets have failed since. They dont usually reccommend this but I never agreed with that so I always do it…works for me… In fact I dont see too many vehicles that have intake gasket failures…the only ones I see are when someone has been into the intake before and NOT changing the gasket upon re-assembly and also not using silicon gasket maker to try and save the old compressed gasket. When that occurs the OP re-install the intake on top of an already compressed gasket thus severely limiting its sealing capability. I will always apply this thin coat of sealer…it just makes sense to me. I have also saved many n old intake gasket by applying this sealant…when a new gasket is not available or handy. Works like a charm…everytime.

No idea why you are seeing such a rash of failures…at least you know what it is and know the solution to the issue. Thats good at least.

In recent years the intakes have become quite complex with several pieces of various materials. Many have cast alloy throttle bodies attached to plastic upper plenums which attach to the lower aluminum manifolds. Often the plastic becomes distorted from heat/cold cycles and looses its clamp on the gasket. There are some expensive gaskets that are designed to make the repair more reliable. If the problem is not taken care of in time catastrophic engine damage will likely result.

I agree,it certainly does appear that the manufactures pick a part that gets to be the decades “chosen part to fail”, in reality it is probably much closer to Rod Nox’s explaination.

You certainly seem to be plagued with this problem, at least according to whoever is doing this work.

An intake gasket leak can cause several problems all depending on where it’s leaking.
Rough idle or engine surge.
Coolant loss and/or coolant diluting the engine oil.

Have your vehicles experienced any of this?

In a nutshell, your Buicks need intake reseal because they’re GM products with engines known for intake manifold leaks and failures. Do a web search for “Dexcool intake gaskets” and see what you find. I think you missed the date for the class action suit by a couple of years.

Your Mystique, if it’s a 6 cylinder, has an intake system that tends to develop vacuum leaks. Not a very good design in my opinion.

Your Jeep, well, it’s a 20 year old Jeep.

Does DEXCOOL cause problems? I havent heard this or maybe never paid attention…I will look into this…

IMO, Dexcool itself does not cause problems. However, as it was explained to me by a GM rep, Dexcool used in a system that is not tightly sealed undergoes some sort of reaction because of the continued presence of oxygen and aluminum. It then allows the formulation of aluminum oxide–the same stuff sandpaper is made of. Then it eats away at the gaskets. The problem with the intake gaskets is that they were originally made of some type of nylon composite embedded with o-rings as the sealing surface. The nylon deteriorated then the o-rings leaked coolant. So as long as the system is tight and has a good cap the coolant is good for over 100,000 miles and offers better heat exchange that conventional green coolant.

Also, the 3.8 engines had a design problem with the plenum. EGR flowed into the plastic plenum. There are 2 coolant passages around the EGR passage to keep it cool, but the hot exhaust ate away at the plastic, eventually resulting in a coolant loss into the intake. I’ve seen hydrolock because of this. Both AC Delco and aftermarket have revised upper intakes for this.

Now I’ve gone on so lone I sound like a wise ass…

I agree with you, it is not the dexcool. And your GM rep is only partly right, if oxygen gets into the cooling system of an aluminum engine, it will form aluminum oxide, but that has nothing to do with dexcool, it will happen no matter what coolant you use. The fact is that dexcool is actually a little better at protecting aluminum engines from this that the older antifreezes were.

The 3.8 engine is a great engine, but everyone we have or have had has needed a new intake manifold at one time or another. My Saturn has also needed a new intake manifold gasket twice now but it had nothing to do with the dexcool. The gasket failed around the #1 cylinder, the only coolant passage is near the throttle body by the #4 cylinder.

Thank you. Dex-Cool is used in all our vehicles. The '90 Jeep Grand Wagoneer got a new engine 14 years ago and all seals were replaced (trusted mechanic). So, the Jeep’s engine is the same age as '96 Mercury and '96 Buick. The '07 Buick was a real mystery. I thought it was the ethanol added to all gas these days that was contributing to gasket failure. The shop who recommends the reseal also forgot to reattach one of the spark plug wires to distributor cap (we discovered after driving 1,500 miles on vacation)and securing battery cables after they had disconnected them while in the shop. Our confidence in this shop is now shaken. I think we will take to another shop for a second opinion. What will happen if seals fail? How will we know when that will happen? Is there a way to test for this? Thank you.

Ahh, the GM 3.8. Best V6 engine ever made by anyone, anywhere. Only the Ford 3.0 Vulcan comes close for reliability, durability, and ease of service. Who else has an engine design spanning almost 50 years of reliable service? I’d run one to the moon and back–as long as the intake has been fixed.

I think my answer is to take the cars to another mechanic to verify these needs. If our regular mechanic hadn’t left one spark plug wire off the distributor cap when they were completely looking over the Jeep before we left for a 1,500 mile drive, we wouldn’t be so unsure. It sounds like our '96 Buick Regal might give us many miles of driving if we get its intake manifold resealed. After we returned from our trip (on return we discovered spark plug wire not connected on our dear v-8, 85,000 mile vehicle)we complained loudly to mechanic. After checking it over completely (again) the intake manifold reseal was recommended.