I apologize if this has already been covered, I went through pages of threads and didn't find anything relevent. I've searched, but 'lower intake gasket' is (unfortuently) a very common topic.

I know that GM released an updated LIM gasket design for the S2 3800, using steel/aluminum with rubber inserts. Does anybody know if GM also updated the design for the S1 LIM gasket, or am I still stuck using the plastic with rubber inserts?

No, they did not change the S1 gaskets. There was no need to. Either the AC Delco or the FelPro gaskets will give you many years of service if properly installed. Particularly if your car isn't converted to DexCool.

I have Dexcool in my 94 Series 1 Do I have to convert back over to green? Or will a Series 2 gasket fit my car?

Having S1 or S2 gaskets should not limit which coolant you use.

Dexcool has been found to break down gaskets over time. Which coupled with heat is why we believe has recently led GM to change the design from plastic frame to aluminum frame.

Many S2 owners have flushed and switched to green coolant.

Personally I have flushed and changed over to Prestone Dexcool "approved" coolant which should not be confused with Dexcool.

However with proper maintenance Dexcool should not turn acidic and hurt the gaskets.

Whats the difference?


I hear Dexcool is good for 100,000 what maintenance can you do to prevent the coolant from becoming too Acidic?

This is all new to me since I never really ever changed coolant in any of my cars I just drove em till something broke :?

jr's3800 has also converted. My personal opinion is that DexCool is the anti-christ.

Have it checked regularly. Othewise change over. Your gaskets will like you for a longer time.

I am very much like you. Learning tons of stuff from the club.

Dexcool has a workable lifespan. What the true amount of time or miles is...I personally don't have that answer. I do know it'* advertised by GM to be something like 5yr 100K. Supposed to be a better coolant. All good things have downsides....ever notice?

I'd plan a 3-4 year or 75K replacement plan on it. With a good flush. Look at some of the pics on the club of peoples under hood. Notice the overflow jug. Dexcool jugs tend to look dirty inside and have rings built up. Both my Dex vehicles have.

The difference between Dex and Prestone "Dex approved" to my knowledge..it'* not the same thing. Therefore probably shouldn't have the same results.

Thank you for the replies and the information regarding the S1 gaskets. I've seen S1 gaskets that have collapsed, but it seems to be much less common than the S2 gaskets failing. After all the miles on my original set of gaskets, I'm very interested in seeing just how bad these gaskets are. Especially considering the crap I have already built up in just a couple thousand miles on cyl #1 spark plug since replacing all the plugs.

Regarding the ring around the overflow tank, I've always been led to believe that this is actually caused by leaking lower intake gaskets allowing oil into the coolant, which is transferred into the coolant tank and leads to the sludge buildup in the tank. I've seen this occur with Dex-cool as well as green coolant, which is why I feel that it is not so much a problem with Dex-cool as it is a problem with the vehicle it is used in.

I'm not saying that I support Dex-cool at all, whenever possible I have switched vehicles over to green, both my own vehicles and my customer'* vehicles.

That is saying that every car we see with this Dexcool sludge has an oil leak. No way can I believe that.

To support the theory where is the oil leak in the lower intake manifold gasket? Remember for the oil to get into the coolant, it must be in an area where the oil pressure is higher than 16psi (The pressure of the coolant system.)

Okay, I'll play along. Say that it'* not an oil leak. What else causes oily buildup in the overflow tank? Is Dexcool made up partially of 5W-30? Last I checked it isn't. And I DO believe that every vehicle with the Dexcool sludge has an oil leak, since the majority of them are GM V-6 or V-8 motors which all have a (surprise!) leaking lower intake gasket.

And what happens when coolant cools down? It creates a vacuum. Is there a chance that some oil could get sucked into the coolant during this state of vacuum? Yes. Is this the definite reason for oil in the coolant? No. I would be interested in seeing what the sludge in the overflow tank is composed of.