ENGINE OVERHEATS
An engine may overheat either because it produces more heat than the cooling system can take care of, or because the cooling system is not taking off all of the heat that it should.
Running an engine with the spark retarded will cause it to overheat; so will a failure of the lubrication and an obstruction to the passage of the exhaust gases.
If an engine has been taken down and overheats when it is reassembled, it may be that the magneto has been wrongly timed, and produces its spark too late. If an engine has been running properly but begins to overheat, the ignition cause will be the faulty setting of the spark control, or the slipping of the spark control rod.
When an engine is run on kerosene, the oil in the crankcase must be frequently drained off and replaced with fresh oil. The reason for this is that part of the kerosene that goes to the cylinders does not vaporize and burn, but works its way past the pistons and into the crankcase, where it thins the lubricating oil. As the oil thins, it loses its ability to lubricate, and the engine begins to overheat.
Anything that produces extra friction will cause overheating, as, for example, a wrist pin that works endways and rubs against the cylinder wall, or a tight bearing.
For a cooling system to work properly it must contain a full supply of water, the passages must be clear, sufficient air must pass through the radiator, and the pump must be in proper condition.
Hose connections will rot, and a strip of rubber may peel off the inside and be drawn across the passage; or if dirty water is used, the dirt may choke the fine radiator passages or other channels. If the radiator is covered with mud, air cannot get at the tubes to take the heat from the water that they contain.
A very usual cause of overheating is a slipping fan belt; an adjustment is provided by which the belt can be tightened when it works loose.