I'm having to add coolant like crazy but I can't figure out where it's going.

Dear Car Talk

Dear Car Talk | Feb 01, 1997

Dear Tom and Ray:

I recently purchased a '79 Ford Mustang 302 V8. The car has only 70,000 miles now, and was originally owned by a little old lady. It's a great car and goes like Leona Helmsley being chased by the IRS. My problem is that it's using coolant. I have to add coolant every three to five days. I find no drips under the car, no leak from the heater core, and no white smoke coming out the tailpipe. Oh, where, oh where has my antifreeze gone, oh where, oh where can it be? -- Dave

TOM: Your "eyeball" methods won't cut it here, Davey, my boy. For instance, your coolant could be leaking only when you drive. Something like a rusted freeze plug might only leak when the engine is at operating temperature and pressure, and not when it's sitting in your driveway.

RAY: Alternatively, while coolant vapor might be coming out the tailpipe (what you describe as "white smoke"), it might not be easily visible.

TOM: You need to take this to a mechanic and have him do a pressure test. Have him get the car up to operating temperature, put a pressure tester on it, and leave it overnight. Then you'll see where it's leaking (and it IS leaking from somewhere).

RAY: If it's not leaking externally (i.e., from a freeze plug, water pump or hose), it has to be leaking inside the engine, in which case your mechanic will find coolant inside one or more of the cylinders.

TOM: In most cases, that would point to a bad head gasket. But we've rarely seen head gaskets blow on these engines, which means the news is worse; it's more likely to be a cracked cylinder head or a cracked block.

RAY: Maybe granny was racing this thing on the weekends? She didn't go by the name Emma Fittibaldi, did she?

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