43555 Mariner BRACKET, TOP COWL

Recommended Procedure A. OUTSIDE LEAKS1. Leaks in Hoses or Connections Check all hoses and connections for visual signs of leakage. If no leaks are seen look for damage to hoses or loose clamps.2. Leaks in the Radiator and/or Expansion Tank Put pressure to the radiator and/or expansion tank with the 9S8140 Cooling System Pressurizing Pump Group and check for leaks.3. Leaks in the Heater Put pressure to the cooling system with the 9S8140 Cooling System Pressurizing Pump Group and check the heater for leaks.4. Leaks in the Water Pump Check 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, install a new water pump.5. Cylinder Head Gasket Leakage Look for leaks along the surface of the cylinder head gasket. If you see leaks, install a new head gasket. B. COOLANT LEAKS AT THE OVERFLOW TUBE6. Bad Pressure Cap Check 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 with the 9S8140 Cooling System Pressurizing Pump Group.7. Engine Runs Too Hot If 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. See "Above Normal Heating" in COOLING SYSTEM chart.8. Expansion Tank Too Small or Installed Wrong The expansion tank can be either 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. Make sure the expansion tank is installed correctly and is according to the recommendations of the Truck Manufacturer.9. Cylinder Head Gasket Leakage, or Crack(s) in Cylinder Head or Cylinder Block Remove the radiator cap and with the engine running look for air bubbles in the coolant. Bubbles in the coolant are a sign of probable leakage at the head gasket. With the engine not running, check each cylinder with the cylinder leakage tester. Special Instruction (GMG00694) gives the test procedure. If you see air bubbles in the coolant during this test, there is a leak of combustion gas into the cooling system. Remove the cylinder heads from the engine. Check cylinder heads, cylinder walls and head gasket surface of cylinder block for cracks. When installing heads, use new head gaskets. C. INSIDE LEAKAGE10. Cylinder Head Gasket Leakage If the cylinder head gasket leaks between a water passage and an opening into the crankcase, coolant will get into the crankcase.11. Crack(s) in Cylinder Head Crack(s) in the upper surface of the cylinder head or an area between a water passage and an opening into the crankcase can allow coolant to get into the crankcase.12. Crack(s) in Cylinder Block Crack(s) in the cylinder block between a water passage and the crankcase will let coolant get into the crankcase.