Cadillac Seville / Cadillac Eldorado Forum Discussion, 2001 STS: Changing antifreeze (Dexcool, evacuation) in Past Cadillac Vehicle Discussion; I'm going for an antifreeze flush tomorrow for my 2001 STS. I put in the red dexcool stuff last time, ...
DEX-COOL, or the all makes, all models "green stuff", it doesn't matter which you use, just change it every 2-3 years.
You'll never get ALL of the coolant out of a Northstar during a coolant change, even if you remove the lower hose. It's not necessary anyway. The point is to replenish the anti-corrosive additives, and a simple drain and fill will do that.
What type of "machine" is this shop using? Does it just remove coolant, or is it some sort of "flush" machine? If so, go somewhere else.
Well if we were talking about a transmission fluid flush, a flush is (potentially) a very bad thing. There's no telling what contaminants were in the fluid of the vehicle that was last hooked up to the machine. That's not nearly as big of a problem with a cooling system, but flakes of rust and leak stop products from other cars aren't the best thing for your car either.
It might be instructional to Google "automotive vacuum coolant flush machine" to find out the fluid removal/replacement process. None of the work involves recycling fluid from another vehicle, and a transmission "flush" will not get the dust and chunks out of the pan: that's what a pan drop/cleaning is for.