To flush or not to flush.

Dear Car Talk

Dear Car Talk | Sep 01, 2002

Dear Tom and Ray:

I've got a 1994 Geo Prizm with about 65,000 miles. It's only been flushed once, at about 15,000 miles. I was advised not to flush it, as it might cause everything to come loose, and I'd need a new radiator, which I can't afford right now. But another mechanic says it is an absolute necessity. When I told my mechanic not to do any flushing, he got really mad and yelled, which made me suspicious. Since I am a woman, I am always afraid that these mechanics are trying to take advantage of my pocketbook. What's the best decision? Flush or don't flush? -- Bonnie

TOM: Gee, and I thought it was only during a drought that you weren't supposed to flush.

RAY: Most flushing these days is done by a machine. Once hooked up, the machine forces out the old coolant, under pressure, and then adds new coolant.

TOM: And it's unlikely to cause you any problems, Bonnie. When being flushed, the radiator is subjected to no more pressure than it is when the engine is running. So you're not putting any undue stress on it. Of course, it's possible that you've got so much crud in there that some of the particulates themselves are plugging up some potential leaks. Occasionally we do see that.

RAY: But any radiator that's being held together by its own crud is not long for this world anyway, Bonnie. Normally, we do recommend flushing the cooling system every 30,000 miles or so. But in your case, we're going to make an exception.

TOM: On an 8-year-old car, you're probably almost due for a radiator anyway. And since money is tight, I think I'd advise you to save the money that you would use for the flush, and start saving for the new radiator you're going to need.

RAY: Flushing the system is good because you remove the contaminants that can eventually block up the radiator and the heater core. But given the age of your current radiator and your financial situation, I'd just ask your mechanic to drain out the old coolant and pour in some fresh stuff. You won't get all of the dirt out, but you'll get some of it, and you'll save yourself a few bucks. And more importantly, you'll have new rust inhibitors in there to keep things from getting any worse.

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