well, I bought a 2001 se7. love it. it overheated the other day for about 30 seconds. checked tank, and there is a orange and white pasty crytal sustance in the coolant tank. coolant ran all over the side of the bay, under the coolant bottle ONLY. now, it gets hot occasionally...maybe once a day for 30 seconds. no coolant loss. system hols pressure. no coolant in oil. anyone know what the residue could be? sounds like the system is getting clogged causibg it to get hot and back out of the overflow line...and then clears. any ideas?

 

This is only a thought......but GM has/had an orange coolant (kind of closein color toRover coolant)called Dex-Cool. I believe that this particular coolant was deemed responsible for tons of cooling system failures in GM's. The problems were verysimilar to what you describe.......a hardening or crystallizing.

Again, only a thought.....but it's possible that, because of it's orange/yellow color, an unknowingowner or shop may have assumed that Dex-Cool wascompatible withLR coolant and put it in your truck. Apparently the coolant had a very different chemical make up and wouldn't/couldn't be mixed with any other coolants, etc.

If this was, in fact, the case, it could also explain the short spells of overheating......as this hardened debris temporarily restricted flow.

Typically, oil in the coolant (via head gasket, etc.) results in a pretty obvious color and texture. In addtion, if it were a head gasket, your overheating would probably be ongoing and accompanied by coolant loss (via internal combustion or exterior leaking).

I'd suggest you start by doing a system flush.