Thermostat Diagnosis. Buick Century (China) (CNG) 1999

GM Service Manual Online

For 1990-2009 cars only

Makes 🢒 Buick 🢒 1999 🢒 Century (China) (CNG) 🢒 Engine 🢒 Engine Cooling 🢒 Thermostat Diagnosis

Thermostat Diagnosis Slow Warm Up

Step	Action	Value(s)	Yes	No
Important: The J 24731 tempil stick is a pencil-like device that has a wax material containing certain chemicals which melt at a given temperature. Use the temperature sticks to determine a thermostat's operating temperature by rubbing 87°C (188°F) and 97°C (206°F) sticks on the coolant outlet. The marks made by the sticks should melt when coolant temperatures reach 87°C (188°F) and 97°C (206°F), respectively. These temperatures are the normal operating range of the thermostat.
1	Remove the radiator cap. Refer to Pressure Cap Description . Rub a 87°C (188°F) J 24731 on the coolant outlet. Warm up the engine at fast idle. Check for coolant flow before the mark begins to melt. Is there coolant flow before the mark melts?	--	Go to Step 3	Go to Step 2
2	The problem is caused from something other than the thermostat. Refer to Engine Fails To Reach Normal Operating Temperature . Does the engine warm up properly?	--	System OK	--
3	Replace the thermostat. Refer to Engine Coolant Thermostat Replacement . Check the system. Does the engine warm up properly?	--	--	System OK

Thermostat Diagnosis Overheating

Step	Action	Value(s)	Yes	No
Important: The J 24731 tempil stick is a pencil-like device that has a wax material containing certain chemicals which melt at a given temperature. Use the temperature sticks to determine a thermostat's operating temperature by rubbing 87°C (188°F) and 97°C (206°F) sticks on the coolant outlet. The marks made by the sticks should melt when coolant temperatures reach 87°C (188°F) and 97°C (206°F), respectively. These temperatures are the normal operating range of the thermostat.
1	Remove the radiator cap. Refer to Pressure Cap Description . Rub a 97°C (206°F) J 24731 on the coolant outlet. Warm up the engine at fast idle. Check for coolant flow before the mark begins to melt. Is there coolant flow before the mark melts?	--	Go to Step 2	Go to Step 3
2	The problem is caused from something other than the thermostat. Refer to Engine Overheating . Does the engine still overheat?	--	--	System OK
3	Replace the thermostat. Refer to Engine Coolant Thermostat Replacement . Check the system Is the engine still overheating?	--	--	System OK