I've had 3 vehicles that had Dexcool that had problems with the sludge. My old 96 Sierra I got from my dad was so bad the radiator was 1/2 clogged and had to be replaced. My dad was clueless on the issues with dexcool. If air got in the system it would gum up like that. Fortunately my recent Trailblazer has already been changed over. My blazer I had to flush twice but saved the radiator. It took 1/2 hour running water through the engine from a garden hose to get the water to run clear. That was including the heater core. After that its easier to just switch back to the green. I've also read a few articles over the years that the original dexcool pH was enough to "eat" away at gasket seals. I have a mind to believe it though I haven't gone so far as to do a test to prove it.

I use Star-Cool in my Blazer. I started with a new engine, new radiator, new surge tank, and a thoroughly flushed-out heater core, so there was no chance of contamination. So far, so good.

I forgot to mention air in the system for sluge. Bad LIM gaskets and lack of monitoring levels can combine for a poor outcome.


George

Just to square the circle, the leak turned out to be the seal on the front of the LIM. It was small for a long while but finally burst through and became obvious. $600 later and I am good.

Did it burst outward or into the lifter valley?

Was the $600 the cost for just the LIM repair?