sign of thermostat failure?
09-06-2004, 01:12 PM
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w210 e240
sign of thermostat failure?
E320 24v
my mb suffers from coolant loss thru (new)reservoir cap with engine off after a long drive. last night i noticed that my temp is around 90 but later on drop to its usual 80s. could this be a sign of an intermittent stucked closed thermostat. for the fast few days, i have to top my reservoir before a long drive twice a day or else my sensor light would turn on.
the engine performance is however is excellent with no signs of coolant leaks on tubings.
why do the coolant overflows thru the cap with engine off on a hot engine.
aux fan are supposed to run for a few mins after turning off the engine but if it fails, what could be thw problem?
thanks for any reply
my mb suffers from coolant loss thru (new)reservoir cap with engine off after a long drive. last night i noticed that my temp is around 90 but later on drop to its usual 80s. could this be a sign of an intermittent stucked closed thermostat. for the fast few days, i have to top my reservoir before a long drive twice a day or else my sensor light would turn on.
the engine performance is however is excellent with no signs of coolant leaks on tubings.
why do the coolant overflows thru the cap with engine off on a hot engine.
aux fan are supposed to run for a few mins after turning off the engine but if it fails, what could be thw problem?
thanks for any reply
09-10-2004, 01:47 PM
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1991 300E
doc *****, My 1992 300E does the same thing. I recently changed the coolant from the green stuf to the Mercedes Benz brand coolant. For some reason when I run the car with the Air Conditioning on it usually stays around 85 deg Celcius, but sometimes it will spike to 100 C. City or highway driving doesn't seem to matter, it has leaked after both. If the temp gets over 100 C then the water will boil out of the resevior cap and into the catch tank under the car. The resevior cap will also try and bleed pressure off. I don't know if I have a bad thermostat, air bubbles in my coolant lines or not a strong enough coolant mix. Any other help would be much appreciated.
09-12-2004, 09:58 AM
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ive changed my thermostat to no avail so i had decided to send her to an MB technician.
i had ignored that the windshield reservoir turns into red or green coolant which i previously thought to be normal.
mb tech found a leak in the washer fluid heater so since we dont use heaters in the tropics, he plugged the line to aux pump and return line from heater with a piece of wood inside to rubber hoses. the line to the washer heater
bifurcates after the aux pump.
i think for boilovers through reservoir, one lesson is to do leak tests even if its non-apparent or unlikely.
you could probably isolate the heater line first by plugging it and start diagnosis from there to lessen sources of invinsible leaks.
i had ignored that the windshield reservoir turns into red or green coolant which i previously thought to be normal.
mb tech found a leak in the washer fluid heater so since we dont use heaters in the tropics, he plugged the line to aux pump and return line from heater with a piece of wood inside to rubber hoses. the line to the washer heater
bifurcates after the aux pump.
i think for boilovers through reservoir, one lesson is to do leak tests even if its non-apparent or unlikely.
you could probably isolate the heater line first by plugging it and start diagnosis from there to lessen sources of invinsible leaks.
09-13-2004, 11:01 AM
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1991 300E
Don't know if your radiator is still boiling through the radiator cap on the expansion tank like my car was, but I found my problem. Inside the neck of the expansion tank is a flat rubber washer that the radiator cap seals onto. This washer was cracked and did not allow the radiator cap to make a proper seal inside the expansion tank. I just tossed it and now the radiator cap seals fine against the inside of the expansion tank neck. No more coolant leaking out.
