Chevrolet Repair: coolant, manifold gaskets, antifreeze brands

Question
I have a 2002 3.4L Cheverolet Venture Van with 54,000 miles. When I bought the van it came with Dexcool extended life coolant (5 years or 150,000 miles). Recently, I had to replace the intake manifold gaskets due to a leak. I have heard that Dexcool may be the cause of leakage problems like this. It also seems that many coolant companies are producing extended life coolant and in fact it is more popular in stores than the regular green antifreeze. Do you know if (1)extended life coolants should be used instead of regular green antifreeze,(It seems that they cause more problems.)and (2)should I replace the extended life coolant in my van with regular green antifreeze to avoid future problem? Thanks

Answer
Hi Tracy,

NOOOO, don't replace the Dexcool with the green.  If these mix in your engine, terrible things will happen.  As I understand it, the two will gel up and turn viscous.  You will overheat.  

The reason for the gasket leak is GM has a problem and won't recall it.  They used a glue at the factory, instead of a sealant.  This glue is not compatible with Dexcool.  Dexcool eats the glue and you develop the leak.  

There are other variations of Dexcool at the corner store.  You can mix the extended life antifreeze brands.  

If you do want replace with the 'old stuff', you first have to do a entire engine flush.  Once all of the Dexcool is out, you can then refill with the green.  Make sure you let mechanics know this from then on.  Otherwise they may put the wrong stuff in when the top you off.  

Hope this helps.

C J S