The first sign of a vehicle overheating is either when the needle on the temperature gauge pushes its way into the ominous red zone or the “Check Engine” or “Temperature” malfunction indicator light on the dashboard casts a sinister glow. Left alone, the liquid in the radiator eventually boils over, and steam rolls out from under the hood.
If your vehicle overheats often and constantly loses coolant, the problem may be leaks in your cooling system. If your vehicle overheats in normal weather and traffic, you may need to add liquid to the system, replace the thermostat, adjust or replace the accessory belt, or check the water pump.
The first thing to check if your vehicle overheats often is the pressure cap. Sometimes the gasket on the cap deteriorates and lets pressure escape, which causes the cooling system to malfunction. Most service stations can test your cap for you and tell you whether it’s in good condition.
Late timing: If your ignition system is malfunctioning, late timing may be causing your vehicle to overheat because the spark plugs are firing the fuel/air mixture after the piston moves back down from the top of its stroke. Late timing alone doesn’t cause an engine to overheat by more than a few degrees, but when coupled with other problems, it can bring the engine temperature to a critical point. Have a service facility place your vehicle on an electronic diagnostic machine to check your timing and adjust it if necessary.
Plugged radiator: Because plugged radiators cut down on the system’s liquid circulation, the system can’t cool efficiently. The remedy is to have a radiator specialist remove and inspect the radiator. If you’re lucky, just steam-cleaning the radiator does the job; if you’re not, the solution may be more expensive.
Slipping accessory belt: If you can see and reach the accessory belt that drives the water pump, check to be sure that there’s no more than about 1⁄2 inch of give. If the belt seems loose or frayed, you can try to replace it. If you can’t do the job, have a professional deal with it.
Collapsing bottom radiator hose: Occasionally, a bottom radiator hose begins to collapse under the vacuum that the water pump creates, and the impaired circulation causes overheating.
Low oil level: A vehicle that’s low on oil tends to overheat because the oil removes from 75 to 80 percent of the “waste heat” in your engine (in addition to doing its other job of cushioning the moving engine parts).