Questions and Answers

Rust In The Cooling System Q. Hi Vince, Hope you can shed some light on an ongoing problem I've been having with my 1996 Chevy Blazer, 4.3 liter V-6, Automatic, P/S, P/B, TBI. with 105,000 miles. After 5 trips back to the dealer (on extended warranty) for flushing, replacement of heater core, and god knows what else, I still have a problem with the cooling system.

The car now needs a water pump, as its leaking from the seals and spitting rusty coolant all over the engine compartment. When I opened the radiator, I found that it was full of what looked like rusty paste. I stuck a hose in the radiator and flushed a lot of that stuff out of there, but I'm sure it's going to take more flushing to get rid of it. I'll try to flush most of it out before I change the pump, to avoid clogging the impeller blades with the gooey stuff.

My question is: Why is this happening?? And how do I avoid the problem altogether?? The dealer filled it with Dexcool® about a year ago when they said it was "fixed", and it seemed to be fine for a while. But now the problems are back. Is Dexcool® less effective at preventing this rust than the old-style Ethylene Glycol?? And would I have better control of this rust by completely flushing the Dexcool® out and refilling it with good old Prestone??? I've never had problems with coolant like I have with this Dexcool®. Hope you can help! And Thanks for your time!!!

A. I don't think the problem is with the anti-freeze. I think it's just the fact that air was allowed to enter the cooling system for an extended period of time and the inside of the block started to rust.

You can fill a cooling system with pure water and it will not rust as long as the reserve tank is full. The full reserve tank prevents air from entering the cooling system which combines with the iron in the block and forms rust.

Once this rust starts it can be difficult to get rid of. Right now your best bet is to have a reverse power flush done. This is the best way to get it out. Then replace the water pump and fill it with dexcool and hope for the best. That's about all you can do. The chances of it working depend on how long air was allowed to enter the cooling system.

Additional Information provided courtesy of ALLDATA