42956A 1 Mercury COVER ASSEMBLY, FLYWHEEL

1. Leaks In Hoses Or ConnectionsCheck all hoses and connections for visual signs of leakage. If no leaks are found, look for damage to hoses or loose hose clamps. Also, check for leaks in accessories such as fuel heaters and transmission oil coolers.2. Leaks In The Radiator And/Or Expansion TankPut pressure to the radiator and/or expansion tank with the 9S8140 Cooling System Pressurizing Pump Group and check for leaks.3. Leaks In The HeaterPut pressure to the cooling system with the 9S8140 Cooling System Pressurizing Pump Group and check the heater for leaks.4. Leaks In The Water PumpCheck the water pump for leaks before starting the engine, then start the engine and look for leaks. If there are leaks at the water pump, repair the pump or install a new pump.5. Cylinder Head Gasket LeaksLook for leaks along the surface of the cylinder head gasket. If leaks are found, remove the cylinder head and install a new head gasket.Coolant Leaks At The Overflow Tube
6. Defective Pressure Cap Or Relief ValveCheck the sealing surfaces of the pressure cap and the radiator to be sure the cap is sealing correctly. Check the opening pressure and sealing ability of the pressure cap or relief valve with the 9S8140 Cooling System Pressurizing Pump Group.7. Engine Runs Too HotIf coolant temperature is too high, pressure will be high enough to move the cap off of the sealing surface in the radiator and cause coolant loss through the overflow tube. If this occurs, refer to the portion, Overheating, of the topic, Abnormal Cooling System.8. Expansion Tank Too Small Or Installed IncorrectlyThe expansion tank can either be a part of the radiator or it can be installed separately from the radiator. The expansion tank must be large enough to hold the expansion of the coolant as it gets warm or has sudden changes in pressure. Verify that the expansion tank is installed correctly and that it is the proper size according to the specifications of the Truck Manufacturer.9. Air Bubbles Present In The CoolantPossible causes:* a damaged head gasket* a crack in the cylinder head* a crack in the spacer block* a crack in one of the cylinder liners* a crack in one of the injector sleevesRemove the radiator cap and start the engine. Check for bubbles in the coolant. If bubbles are present, then begin engine disassembly. Remove the cylinder head and check for cracks in the internal components. Follow the disassembly procedures as outlined in 3176 Diesel Truck Engine Disassembly and Assembly, Form. No. SENR3914.Internal Leakage
If coolant is found in the engine oil check the following internal components for damage:10. Cylinder Head Gasket LeakageIf the cylinder head gasket leaks between a water passage and an opening into the crankcase, coolant will enter the crankcase.11. Cracks In The Cylinder HeadCracks in the upper surface of the cylinder head, or in an area between a water passage and an opening into the crankcase, can allow coolant to enter the crankcase.12. Cracks In The Spacer BlockCracks in the spacer block between a water passage and an opening into the crankcase can allow coolant to enter the crankcase.13. Cylinder Liner LeakageA damaged or missing liner seal can allow coolant to enter the crankcase. Replace any seals as needed. A cracked cylinder liner can also allow coolant to enter the crankcase. Check the liner for cracks and replace as necessary.If coolant is found in the fuel, remove the unit injectors and check the injector sleeves for cracks.14. Defective Injector SleeveCorrosion or cracks in the injector sleeve can permit fuel to enter the coolant and also can allow coolant to enter the fuel supply manifold. It is also possible for combustion gas to enter the cooling system due to a leak in the injector sleeve. When this condition exists, the coolant level generally increases and exits the overflow.