The must maintained auto radiator keeps your cars in good condition. Neglects could caused a little damage costly before you diagnosed it so some precautions should be remembered. Example is to check the fan if it works well especially when hot weather comes. The distance of the fan may lessen the cooling ability so engine gets hot.
Thermostat - Severe overheating can often damage a good thermostat. If the engine has overheated because of another problem, the thermostat should be tested or replaced before the engine is returned to service.
One way to check the thermostat is to start the engine and feel the upper radiator hose (or use an infrared non contact thermometer to read its temperature). The hose should not feel uncomfortably hot until the engine has warmed-up and the thermostat opens. If the hose does not get hot, it means the thermostat is not opening.
Another way to test the thermostat is to remove it and dip it into a pan of boiling water (it should open). The exact opening temperature can be checked by using a thermometer.
If the thermostat needs to be replaced, install one with the same temperature rating as the original. Most cars and light trucks since 1971 require thermostats with 192- or 195-degree ratings. Using a cooler thermostat (160 or 180) in an attempt to "cure" a tendency to overheat can increase fuel and oil consumption, ring wear and emissions. On newer vehicles with computerized engine controls, the wrong thermostat can prevent the computer system from going into closed loop resulting in major performance and emission problems if the engine fails to reach its normal operating temperature.
- Cooling system leaks - Loss of coolant because of a leak is probably the most common cause of overheating. Possible leak points include hoses, the radiator, heater core, water pump, thermostat housing, head gasket, freeze plugs, automatic transmission oil cooler, cylinder head(s) and block.
Make a careful visual inspection of the entire cooling system, and then pressure test the cooling system and radiator cap. A pressure test will reveal internal leaks such as seepage past the head gasket as well as cracks in the head or block. A leak-free system should hold pressure for at least a minute or more.
It’s important to pressure test the radiator cap, too, because a weak cap (or one with too low a pressure rating for the application) will lower the coolant’s boiling point and can allow coolant to escape from the radiator.
- Fan - With mechanical fans, most overheating problems are caused by a faulty fan clutch - though a missing fan shroud can reduce the fan’s cooling effectiveness by as much as 50 percent (depending on the fan’s distance from the radiator), which may be enough to cause the engine to overheat in hot weather or when working hard.
Defective fan clutches are a common and often overlooked cause of overheating. The shear characteristics of the clutch fluid gradually deteriorates over time, with an average loss in drive efficiency of about 200 rpm per year. Eventually slippage reaches the point where effective cooling is no longer possible and overheating results. (On average, the life of a fan clutch is about the same as a water pump. If one needs to be replaced, the other usually does too.)
If the fan clutch shows signs of fluid leakage (oily streaks radiating outward from the hub of the clutch), spins freely with little or no resistance when the engine is off or wobbles when the fan is pushed in or out, it needs to be replaced.
With an electric cooling fan, check to see that the fan cycles on when the engine gets hot and when the air conditioner is on. If the fan fails to come on, check the fan motor wiring connections, relay and temperature sensor. Try jumping the fan directly to the battery. If it runs, the problem is in the wiring, relay or sensor. If it fails to run, the fan motor is bad and needs replaced.
- Water pump - Any wobble in the pump shaft or seepage would call for replacement. In some instances, a pump can cause an engine to overheat if the impeller vanes are badly eroded due to corrosion or if the impeller has come loose from the shaft. The wrong pump may also cause an engine to overheat. Some engines with serpentine drive belts require a special water pump that turns in the opposite direction of those used on the same engine with ordinary V-belts.
- Belts & hoses - Check belt tension and condition. A loose belt that slips may prevent the water pump from circulating coolant fast enough and/or the fan from turning fast for proper cooling.
The condition of the hoses should also be checked. Recommend new hoses if the old ones are over 5 years old.
Sometimes a lower radiator hose will collapse under vacuum at high speed and restrict the flow of coolant from the radiator into the engine. This can happen if the reinforcing spring inside the hose is missing or damaged.
- Radiator - The most common problems radiators fall prey to are clogging (both internal and external) and leaks. Dirt, bugs and debris can block air flow through the core and reduce the radiator’s ability to dissipate heat. Internal corrosion and an accumulation of deposits can likewise inhibit coolant circulation and reduce cooling. A good way to find clogs is to use an infrared thermometer to "scan" the surface of the radiator for cold spots. If clogged, the radiator should be removed for cleaning or be replaced.
Backflushing the cooling system and/or using chemical cleaners can remove rust and hard water scale, but may do little to open up a clogged radiator.
When refilling the cooling system, be sure you get it completely full. Air pockets in the head(s), heater core and below the thermostat can interfere with proper coolant circulation and cooling. If the cooling system has no bleeder valves to vent air, you may have to temporarily loosen a heater hose to get all the air out of the system.
- Excessive exhaust back pressure - A clogged catalytic converter is usually the culprit here, but don’t overlook the possibility of a crushed pipe or a collapsed double wall pipe. Check intake vacuum at idle. If it reads low and continues to drop, inspect the exhaust system.
- Retarded or over advanced ignition timing (may also contribute to detonation and preignition).
- Overheated incoming air - On older vehicles with a carburetor or throttle body injection, check the operation of the heated air intake system on the air cleaner. If the temperature control valve is stuck so only heated air from around the exhaust manifold is drawn into the air cleaner, it may contribute to detonation and/or overheating. Also check the heat riser valve for manifold heat on older V6 and V8 engines. If stuck shut, it may be overheating the intake manifold.
- Dragging brakes - A caliper that’s sticking or a parking brake that isn’t releasing may be making the engine work too hard.
- Overworking the engine. The cooling systems in many passenger cars today are marginal and have little excess capacity to handle extra heat generated by towing or high speed mountain driving in hot weather.