Filling a cavity is always better than waiting until you need a root canal.

Dear Car Talk

Dear Car Talk | Sep 01, 1992

Dear Tom and Ray:

I have a 1987 Chevrolet Cavalier with a four cylinder engine and 53,000 miles. My problem is it loses antifreeze, but only in the coldest weather. You can see wetness under the car, and I have to add more fluid sometimes after only 50 miles. It never loses antifreeze in warm weather. This happens every winter. It seems to help if I keep a lower level in the antifreeze tank. Of course, when I explain the problem to a mechanic, the answer is always a pressure test and the threat of a new radiator core. Before I do something dumb like that and then still have the same problem, can you suggest anything else for me to do?

TOM: We suggest you do the pressure test, William. Don't be a chicken. I once avoided the dentist for a year and a half because I was afraid he was going to tell me I had a cavity. I did have a cavity, but by the time I got to the dentist, I needed a root canal.

RAY: So do a pressure test, but make sure you do it under the conditions in which the car leaks--in this case, outside in the cold weather. If the mechanic does it in his warm garage, where it's probably 65 degrees, the coolant won't leak and you'll never find the problem.

TOM: It sounds like something is shrinking in the cold weather. We know that things shrink when they get cold. Then, once the engine runs for a while and things heat up, whatever it is expands and the leak stops. It could be a seal on the water pump, a crack in the overflow bottle, or something as simple as a bad hose or hose clamp.

RAY: Whatever it is, if it's an external leak, a pressure test will certainly find it. So stand up for yourself, William, and get it fixed. No one should have to take a leak like this lying down!

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