SPRING 4L9971 - Caterpillar

Replace the Water Temperature Regulators in the Water Temperature Regulator Housing and in the Thermostatic Valve
Illustration 1 g00787738Replace the water temperature regulators before the water temperature regulators fail. This procedure is a recommended preventive maintenance practice. Replacing the water temperature regulators reduces the chances for unscheduled downtime.A water temperature regulator that fails in a partially opened position can cause overheating or overcooling of the engine.A water temperature regulator that fails in the closed position can cause excessive overheating. Excessive overheating could result in cracking of the cylinder head or a seizure of the pistons.A water temperature regulator that fails in the open position will cause the engine operating temperature to be too low during partial load operation. Low engine operating temperatures during partial loads could cause an excessive carbon buildup inside the cylinders. This excessive carbon buildup could result in an accelerated wear of the piston rings and wear of the cylinder liner. Also, a low temperature can allow moisture to condense in the oil. This condition can form damaging acids.
Failure to replace the water temperature regulator on a regularly scheduled basis could cause severe engine damage.Never operate an engine without the water temperature regulator installed.If the water temperature regulator is installed incorrectly, the engine may overheat, causing cylinder head damage. Ensure that the new water temperature regulator is installed in the original position.
For the procedure to replace the water temperature regulators, see the Service Manual, "Disassembly and Assembly" module. Consult your Cat dealer for assistance.Note: If only the water temperature regulators are replaced, drain the coolant from the cooling system. Drain the cooling system to a level that is below the water temperature regulator housing.