Over the years there has been a lot of talk about Lower Intake manifold gasket failures. Dex-cool has taken the brunt of this myth. I decided about a year ago to do a year long experiment that would help shed some light on this issue. During this time I also did a lot of research. And now that I have finished this little experiment, I want to share my findings. My observations involve a few cars, but mostly my own.

First up, a LIM gasket failure. This is a plastic framed gasket, standard on our engines. Running Dex-cool, again, standard on our engines. For about 95,000 miles. Please note there is green coolant in this engine. I had flushed the system shortly before changing the gaskets.


Here is a close up. This is a classic failure. The belief is, Dex-cool was acidic and caused the gaskets to soften and fail.


The common fix for this was to drain, flush and refill your coolant system with a common green coolant. The problem with this is if you don't get all the Dex-cool out, it will react with the new green coolant and sludge up.

This here is the same style of plastic framed gasket. The difference here is this is about 12,000 miles using Peak green coolant. As you can see, there is a classic failure starting.


It is obvious that changing coolant did not correct this problem.

Now, these gaskets are the new aluminum framed gaskets. These were from a engine running Dex-cool. As you can clearly see here, there is no sign of classic failure.


It should be clearly obvious that changing the gaskets to the new aluminum style fixed this problem.

This article has been presented to you to help you make a good, educated decision on what is best for you engine. It is my advice that changing the LIM gaskets to the aluminum style is the best choice. There is no reason to change your coolant type. Don't fall in to the hysteria that you must change your coolant. What you do with this information is totally up to you.

I will keep adding more images as they come in.

Plastic framed gaskets with Dex-cool, unknown miles

Dan, that'* one of the best things I've seen written on this subject. It'* informative with facts and you aren't biasing the information. More supplying us with this is what happened with X miles of this coolant and X miles of that coolant.

To further provide info on this, I've seen a fair number of Series I motors with the same gasket "failures" was the ones you show in the pictures. I also had a set of the plastic gaskets swapped in on my motor for 40,000 miles and noted the same beginning of a "failure" like you did on your swapped gaskets. I had changed to an AnyColor coolant after a massive system flush. Like your findings any aluminum framed gaskets that have been removed here have looked new at up to 50,000 miles so far. I have not had the opportunity to see any beyond the 50K mark.

If you have any other pictures and info to go along with them, I will add them to this.

You know this could be very helpful... Seeing as my coolant levels have been dropping lately....

Nice work Dan. Can we get a copy of this without comments into the Tech Database and add pictures as they come available? We could buildup a case-history there.

That was kind of my plan. Just wanted to get the ground work laid out first

I have heard that alot of people switch out of dex cool because dex cool has been known to eat our hoses up.

Great info Dan and free from personal opinions, hysteria and the hype that we have all heard. Nicely done!

on my 94 gmc truck i have ran dexcool in it for 100,000 miles and still to this day no leaks. Still to be determined on my 3.8. I believe its the gaskets and not the coolant.

The series one engines did indeed come with those cheap plastic gaskets. I'm about to do a set on my bro'* 3300 in his cutlass.

Victor-reinz has a graphite gasket far superior to the plastic ones. I have em in my PA.