Question about 1992 Mercedes-Benz Mercedes Benz 300 Class

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1990 300c overheating. Are both electric fans supposed to come on? Any help would be appropriated. There is no coolant in oil or out the tail pipe as far as i can tell. Has hesitation. Temp keeps going 3/4 to full .

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I assume you have checked the cooling system to ensure that first, that it is completely full of coolant (not just the overflow tank) with no air locks and second that there are no leaks anywhere and the radiator cap is in good condition. The heater hoses and those pesky little bypass hoses in the cooling system tend to go hard and split if they are over 10 years old, allowing coolant loss. Those spring type hose clamps tend to be less effective in clamping as the hoses become hard. Worm drive ones are the best to use. Both cooling fans operate together on most larger cars.

If there are no leaks or air locks, the over heating could also be caused by a clogged radiator (more than 15% restriction in the radiator flow capacity will cause overheating problems), a faulty water pump or a faulty thermostat.

If there are no leaks and water pump and thermostat are working correctly, but undetected loss of coolant once the engine heats up, then it could indicate a problem with the head gasket (Usually caused by allowing engine to become excessively overheated when cooling system has run dry) allowing very hot high pressure combustion gases into the engine water jacket, which super heats the coolant in the engine block, which then boils off, and is released via the cap.

If unsure take vehicle to a cooling system specialist and have them do a pressure test and more thorough diagnosis.

Posted on Sep 30, 2010


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