October 1990

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Dear Tom and Ray:
I have a 1979 four cylinder Mustang. After I've been driving for 30 to 40 minutes, I hear a "grinding" sound when I accelerate. When this happens, I also smell something burning. Help!
Gilda

TOM: Gee, Gilda, it could be any number of things. The first one that comes to mind is that your car is overheating. When your engine overheats, it pings like crazy, especially during acceleration. Even though you describe the noise as "grinding," what you hear could be loud pinging (also known as "knocking").

RAY: The burning smell could also be related to overheating. If you've been leaking oil from the valve cover (which is very common with these engines), the oil--which has dripped onto the engine--could heat up and smoke when the engine gets hot.

TOM: Another theory is that your water pump bearings are gone. A failing water pump would make a grinding noise. It would be grinding all the time, but you'd be more likely to notice it (because it would be louder) during acceleration.

RAY: When the water pump bearings fail like this, it's not uncommon for the pump to leak coolant. The coolant would come out as steam, and that could also be what you're smelling.

TOM: At the risk of sounding forward, Gilda, I'd have to say that it's about time you got this sled to a mechanic. Loud grinding noises and burning smells are not symptoms about which one should sit down and compose a letter. These are calls to action. If your house were on fire, you wouldn't sit down and write a letter to the fire department, would you?

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© 2006 by Tom and Ray Magliozzi and Doug Berman. Distributed by King Features Syndicate, Inc.

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Auto repairs can be costly! Save money by ordering Tom and Ray's pamphlet: "Ten Ways You May Be Ruining Your Car Without Even Knowing It!" To order, send (check or money order) to Ruin, P.O. Box 536475, Orlando, FL 32853-6475. You can also order online.