Started a LIM gasket replacement on my 1998 LeSabre. This was meant to simply be "preventive maintenance," as the car was showing no overt symptoms (e.g., loss of coolant, etc.), though it did seem to lack a bit of "pep" (compared to my wife'* 2004 LeSabre) and Scans suggested a possible vacuum leak (consistently high LTFT'*), though I could find no such leak.

Well check this out:




Note part of the old plastic gasket stuck to the head, and part stuck to the LIM.

Also check out these "plugs" left behind in the heads by the Dex-Crap:




Here is a beautiful new aluminum gasket:



Let'* see that sucker disintegrate like the crappy plastic one did.

Moral of the story: Even if you don't think you need to replace your plastic LIM gaskets, do your engine (and your wallet) a favor and change them out!

that is why the GM techs call DEX Mississippi Mud, also shows other members why we recommend that they should remove the DEX in there Vehicles

How did you flush all that out? reassemble then flush? or scrape what you could and cross your fingers?

Well, just goes to show ya that some things don't need fixin. Ethylene Glycol and water has been the coolant of choice for 100 years. Comming up with a "new and improved" coolant wasn't really such a hot idea after all.

Those "plugs" are remnants of some sort of "leak filler" GM dealers stick in the coolant to try to cover up the fooked up gasket issue.
It'* the same junk that leaves that "bathtub ring" in your coolant overflow bottle.

(I learned about that on this site )

I am going to try to "pick" those out without letting them fall down into the heads.

Wow, that is awesome. Thanks for sharing. I am tearing into mine next week to do the same thing. No overt signs or symptoms yet but just like you said, you never know when there is going to be a problem. I will check mine out and keep it posted too.

that is really bad. the coolant passage is blocked!!!???

I am sure glad mine did not come with DEX Cruel

Edited to add, its really interesting to see how the gasket shows deterioration around the coolant passages, but not around the intake ports. Is the trusty green stuff in your plans?

While the buildup was bad, I thnk the two plugged up passages are the ones that dead end on the manifold flange. (On the 3800, only two of the four coolant passages in the heads match up with the crossover in the manifold)

Now, is Dex-Cool corrosive? When I took down my project motor, the cast aluminum rear cover was severely pitted where it seals the coolant passages in the block. Kinda like the Dex-Cool ate the aluminum,

Great pix, Andrew. Just one more example of why this needs to be done. And, why it needs to be done "before it needs to be done!" With some nice green coolant, aluminum LIM gaskets and a heat-shielded upper, you should be able to kiss this problem goodbye. Your bearings are saying: "Thanks Boss - that was a close one!" The crappy condition of the plastic LIM gaskets in Dex never ceases to amaze. Thanks for sharing.