13402 Mercury SCREW

Water Temperature Regulator (Thermostat)
Replace
Replacing the water temperature regulator prior to failure is a recommended preventive maintenance practice because replacing the water temperature regulator reduces the chances for unscheduled downtime.Depending on the engine operating load, a water temperature regulator that fails in a partially opened position will cause either overheating or overcooling.If the water temperature regulator fails in the closed position, the failure will cause excessive overheating. Excessive overheating could result in cylinder head cracking or piston seizure problems.If the water temperature regulator fails in the open position, the failure will cause the engine operating temperature to be too low during partial load operation. Low engine operating temperatures during partial load operation could cause an excessive build up of carbon inside of the cylinder. This excessive build up of carbon could result in accelerated wear to the piston ring and the cylinder liner.
Failure to replace the water temperature regulator on a regularly scheduled basis could cause severe engine damage.Caterpillar engines incorporate a shunt design cooling system and require operating the engine with a water temperature regulator installed.If the water temperature regulator is installed wrong, the engine may overheat, causing cylinder head damage. Ensure that the new water temperature regulator is installed in the original position. Ensure that the water temperature regulator vent hole is open.DO NOT use liquid gasket material on the gasket or cylinder head surface.
Refer to the Service Manual for the temperature regulator replacement procedure, or consult with your Caterpillar dealer. If replacing water temperature regulators ONLY, drain the coolant from the cooling system to a level below the water temperature regulator housing.
Fill the cooling system at a rate of 19 L (5 US gal) or less per minute in order to avoid air locks.
Refer