Cool Solution for an Overheating Problem

Times Staff Writer

Question: I have a 1983 Toyota Camry that gets hot while going up hills and also when idling. I have had the radiator flushed out, the antifreeze replaced and the fan motor checked. I have had it to three mechanics and they can offer no explanation.--D.P.

Answer: Your Toyota appears to be overheating at times when the cooling system is exposed to the maximum heat load generated by the engine. Your mechanics should have checked such potential problems as a faulty thermostat or a faulty water pump.

In many cases, a car's cooling system can be seriously degraded if the coolant inside the radiator and engine block is not regularly changed, as outlined in the owner's manual. Even though it's winter now, you shouldn't ignore the potential for overheating in your cooling system.

Old coolant can become contaminated and create a coating called shale inside the cooling system. The shale literally creates a layer of insulation that prevents the normal exchange of heat from the engine to the coolant.

You said you have had the radiator flushed out. I suggest that you have a two-stage chemical back flush of the cooling system performed. This flush contains caustic chemicals that will dissolve the shale and restore the normal ability of your engine block to pass heat to the coolant.

One other possible cause to your problem is damage to the water pump. If you have not changed your coolant for a prolonged period of time, acidic buildup in the coolant can eat away at the water-pump impeller. That will reduce the volume of water that the pump circulates through the engine, resulting in overheating in high engine-load conditions.

Q: I own a 1980 Buick Le Sabre Limited, which has 70,350 miles on it. Almost from the first, the car began to stall out after driving 20 to 30 minutes at freeway speeds. It often dies as I come to the end of an off-ramp. I have had it to three Buick dealers, but none of them could find the problem. By pumping the accelerator, I have managed to keep it from dying on the freeway. Can you please help me resolve this problem?--G.W.M.

A: The problem you describe is not a known defect in your Buick, and it could be caused by a variety of faulty parts or systems. But there are several things that your mechanic should have checked.

The simplist cause is a partially clogged fuel filter. At freeway speeds, gasoline consumption peaks, and a partially clogged fuel filter usually makes itself known under these conditions.

If the exhaust gas recirculation valve is sticking, it will cause the problem you describe. It could be overcome by pumping the accelerator. But depending on the accelerator pump could get you into trouble. Get the problem fixed.

Q: The tachometer on my car has a red area that starts at 6,000 revolutions per minute. Does that mean it is safe to drive it at that engine speed?--B.B.

A: Just because the red line begins at 6,000 rpms doesn't mean you should normally take the engine up to that speed. In fact, speeds that high will cause premature engine wear.

Most car engines, even those with four-cylinder engines that operate at higher rpms, seldom need to go higher than 3,000 or 4,000 rpms in normal driving. In fourth or fifth gear, they can usually cruise at 55 miles per hour and operate at below 3,000 rpms.


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