This week: How to determine if your heat gauge's busted.

Dear Car Talk

Dear Car Talk | Aug 01, 1989

Dear Tom and Ray:

I have a 1973 Ford F250 Pick-Up with a V-8 and super cooling. I've put in a new radiator, hoses, thermostat, sending unit, dash gauge, fan clutch, and water pump and still the heat gauge reads 3/4 to "hot" in stop-and-go traffic. Strangely, when the temperature gauge goes to hot, the radiator doesn't sound like it's boiling. Do you have any idea what my problem could be?

RAY: Even though you replaced the sending unit and the gauge, you should first double-check to determine that you are getting an accurate reading of the engine temperature. Go out to an auto parts store and buy yourself an automotive thermometer.

TOM: Better yet, steal your wife's cooking thermometer out of the top drawer in the kitchen. Remove the radiator cap, and let the engine idle with the thermometer sticking into the fluid. After an hour or so, check the temperature of the coolant. If it reads 180-190, the engine is fine and either the new sending unit or the gauge are faulty.

RAY: If the coolant registers "well done," however, your problem may be more serious. You may have a cracked or plugged block. A block test will answer that question. And don't forget to wipe off the thermometer off before you put it back, unless you like Turkey a la Ethylene Glycol.

Get the Car Talk Newsletter

Got a question about your car?

Ask Someone Who Owns One