Pinpoint Test A : Loss Of Coolant

Normal operation and Fault Conditions 

The engine cooling system is a closed system providing for coolant expansion and contraction as well as changes in pressure as coolant warms and cools with engine operation. Various gaskets, seals, hoses and clamps contain coolant within the cooling system and keep other fluids and contaminants from entering the cooling system.

Coolant loss can be attributed to either external or internal leaks anywhere within the cooling system.

Possible Sources 

• Coolant hoses or tubes
• Hose clamps
• Thermostat O-ring seal or gasket
• Coolant pump O-ring seal or gasket
• Thermostat housing
• Radiator
• Transmission fluid cooler (in radiator)
• Pressure relief cap
• Coolant pump leaking from weep hole
• Heater core
• Engine gaskets (may leak internally or externally)
• Degas bottle
• Cylinder block core plugs
• Cylinder head core plugs
• Block heater (if equipped)
• Oil cooler (if equipped)

1. WARNING: Always allow the engine to cool before opening the cooling system. Do not unscrew the coolant pressure relief cap when the engine is operating or the cooling system is hot. The cooling system is under pressure; steam and hot liquid can come out forcefully when the cap is loosened slightly. Failure to follow these instructions may result in serious personal injury.
2. A1 CARRY OUT INSPECTION AND VERIFICATION
   
   
   • Carry out Inspection and Verification  .

   Are any concerns present? 

   Yes	REPAIR as needed.

   No

   GO to  A2

3. A2 CHECK THE ENGINE COOLANT LEVEL AND PRESSURE TEST THE ENGINE COOLING SYSTEM
   
   
   NOTE: Allow the engine to cool before checking the engine coolant level.
   • Ignition OFF
   • Visually inspect the engine coolant level at the degas bottle and adjust as necessary. Pressure test the engine cooling system. Refer to Cooling System Pressure Test  .

   Does the engine cooling system leak externally? 

   Yes	REPAIR or INSTALL new components.

   No

   GO to  A3

4. A3 CHECK THE ENGINE COOLANT FOR AN INTERNAL LEAK
   
   
   • Inspect the engine coolant in the degas bottle for signs of engine oil or transmission fluid.

   Is engine oil or transmission fluid evident in the coolant? 

   Yes	If coolant is in the engine oil, REFER to: Engine . If coolant is in the transmission fluid, INSTALL a new radiator. REFER to: Radiator . REPAIR the transmission as necessary. For 6R100, REFER to: Diagnosis By Symptom - 6R100 . For 6R140, REFER to: Diagnosis By Symptom - 6R100 .

   No

   GO to  A4

5. A4 CHECK THE ENGINE OIL AND TRANSMISSION FLUID FOR COOLANT
   
   
   • Remove the oil level indicator from the engine and the transmission.

   Is coolant evident in the engine oil or transmission fluid? 

   Yes	If coolant is in the engine oil, REFER to: Engine . If coolant is in the transmission fluid, INSTALL a new radiator. REFER to: Radiator . REPAIR the transmission as necessary. For 6R100, REFER to: Diagnosis By Symptom - 6R100 . For 6R140, REFER to: Diagnosis By Symptom - 6R100 .

   No

   GO to  A5

6. A5 CHECK THE COOLING SYSTEM FOR COMBUSTION GASES
   
   
   NOTE: Use UView® Combustion Leak Tester part number UVU560000-R or equivalent.
   • Using a cooling system combustion gas leak tester, following the instructions supplied with the tester, check the coolant for combustion gases.

   Are combustion gases present? 

   Yes	REFER to: Engine .

   No	The cooling system is operational.