1993 merc 500 coupe overheating

[smoothcoupe]

hi guys my merc 500 seems to be overheating, the temp gauge goes close to 120 degrees in traffic... but on motorway seems fine (into 90 95 degrees). and today when reached home i could hear boiling noise from the resovoir.... what could it possibly be and is there a bleed valve or screw any where on this car.. where would i drain the cooling system from.. and what is the procedure for replacing the coolant/bleeding etc... help would be appreciated.

 

[grober]

Cooling Fan Problem

My guess is that some or all of your cooling fans aren't working. this could be main fan viscous coupling failure or failure of electric fans or their associated control circuitry/Relays. see http://pages.prodigy.net/jforgione/MB_S500.html or search the forum. Do a static "carrot" test---start car from cold let it heat up then monitor the temp. as it rises the main cooling fan clutch (viscous or electric) should cut in. the fan will spin even at the begining but can be stopped by a carrot (rather than your finger) when the clutch engages the carrot is severed. be careful doing this there are lots of high speed devices ready to "grab/mince" any loose clothing/tie/hair/fingers. the main cooling fan is mounted on the engine. the 2 electric fans in front of the radiator are for the air-con. thtas my guess based on the fact that the car overheats when moving slowly when the fan is required to provide an adequate flow of air. If your not happy working under the bonnet of a car leave it to a pro. good luck

 

[KLP 92]

I think the prob maybe a bit more serious than just the cooling fans. If the thermocoupling fan doesn't work then at 105'C the twin electric fans should cut in. I've had a 500 before where both the electric fans and coupling fan didn't work, the temperature only came up to 110'C.

I wouldn't advise driving the car when the temperature is that high as you will end damaging the engine.

 

[KLP 92]

Also the temp on the motorway should be 80-85'C. 90-95'C is a bit high. I would recommened starting by what forum member Grober has recommended, then i would check the radiator for blockages, the water pump, thermostat etc. If its none of the above run a compression check to be on the safe side.

Also when the temp is at 120'C do you hear the electric fans kicking in? If it does get this hot i would advise putting the heat temp on max on the heater to try and cool it down.

 

[guydewdney]

i tell you what surprised me - i had the air con radiator replaced - and the temp (engine) dropped by a good 10 degrees - im guessing due to dead birds etc stuck int he gaps ...

try giving it a good clean (loosen the rads off a bit, remove grill, get the hose out) - free - worth a try?

then - on the SWMBO's sprinter - went through everything - new thermostat etc etc - turned out to be a dead viscous fan coupling (stopped when hot using but a small twig)