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Ask Dave Nova Your Own Question
Dave Nova
Dave Nova, Buick Technician
Category: Buick
Satisfied Customers: 19451
Experience:  ASE Master Certification. GM World Class Certification
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93 BUICK CENTURY. Radiator cooling fan wont come on when engine

Customer Question

93 BUICK CENTURY. Radiator cooling fan won't come on when engine is hot. If sensor is unplugged fan comes on when engine is running. If engine is turned off fan will not operate.
Submitted: 7 years ago.
Category: Buick
Expert:  Dave Nova replied 7 years ago.
Unplugging the sensor and having the fan come on shows that all the wiring and the computer and the fan are operational. My suggestion is to replace the coolant temperature sensor.
Customer: replied 7 years ago.
Hi Dave, Thanks for the reply. I have tried to order a new sensor for the 93 Buick Century 2.2 Litre and it is no longer available from GM,NAPA,Car Quest, and Auto Zone. Still not sure if that is the problem. After running the engine and getting it to operating temperature then shutting the engine off the radiator coolant recovery tank bubbles and gurgles like the engine is overheating. I have checked the temperature with an infared Snap-On thermometer at the thermostat housing and it reads 188 degrees which is about right. The cooling system doesn't seem to have any pressure on the radiator hoses Would a plugged radiator cause a problem like this? If the radiator is plugged you would think that the fan would operate.
Expert:  Dave Nova replied 7 years ago.
The computer will turn on the cooling fan when the coolant temperature reaches 230 degrees and will turn the fan off again when the temperature drops to 215 degrees. Make sure the coolant mix has plenty of antifreeze in it, otherwise it will boil before reaching 230 degrees. If the radiator were plugged the temperature would far exceed the 230 degrees and the fan should come on.
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Customer: replied 7 years ago.
Thanks David, I think I found the problem. The radiator cap had all kind of crud in the neck and on the rubber seal of the radiator cap. Since the system did not build up much pressure when the engine was at operating temperature when the engine was shut off the coolant would expand and dump the expanded coolant into the coolant recovery tank and cause a bubbling gurgling sound making me think the engine was overheating. Thank you for the valuable info on the temperature sensor (range sensor operates in) actually all the problem was was a defective seal at the radiator cap. Thanks againCustomer
Expert:  Dave Nova replied 7 years ago.
Glad you were able to find the problem. This buildup is common on vehicles with Dexcool.