W204 C63 overheating issue

[Hallett]

Hi everyone, I’m having an issue at the moment with the coolant temperature getting very hot and ultimately finishing with coolant out of the expansion tank cap. Weirdly it seems to hold 95 degrees (which I’m sure is hotter than previously) when in comfort but when you change the gearbox to manual it seems to then overheat very quickly, no codes when plugged into the computer and have changed the thermostat so far with no difference! Hoping someone else has had or heard of a similar issues before, thanks

Dan

 

[mondo111]

Hi everyone, I’m having an issue at the moment with the coolant temperature getting very hot and ultimately finishing with coolant out of the expansion tank cap. Weirdly it seems to hold 95 degrees (which I’m sure is hotter than previously) when in comfort but when you change the gearbox to manual it seems to then overheat very quickly, no codes when plugged into the computer and have changed the thermostat so far with no difference! Hoping someone else has had or heard of a similar issues before, thanks

Dan

95 is above normal temp

 

[Bert_W164]

This isn't normal, when you say finishing with coolant out the expansion tank do you mean it's pressuring and spewing out?

If so really bad sign, is there any oil or mayo on the coolant cap? Does your car misfire? When you say computer, do you mean Star or one of those obd readers?

Basically if it's a pressure issue most likely the heads need to be checked ASAP, particularly the gaskets. You could try and flush the system and see how you get on, if it's still pressurising then you need to do a sniff test on the coolant, this is done by a special tool that'll change colour showing combusting gasses present, in which case it's time to investigate and get the mad scientist to rip out that head gasket you fried.

 

[Stocious]

Try this and tell us the result, let the car boil, I know it sounds daft, but let it sit overnight, start the car cold and watch the exhaust, and listen to the engine, , also just so your aware if a head gasket has failed if also it’s failed between cylinders it can burn a track into the head making it beyond its service life, , don’t drive the car and do what I said and tell us

 

[Stocious]

Or if you’d like to try a test now, leave the cap off the bottle, and get someone to start car, if it starts burping coolant out there ya go,

 

[Jobsworth]

What year is your car? Broken head bolts usually manifest with coolant in the sump, but I suppose combustion gasses forced into the coolant when working hard is a possibility

 

[Hallett]

Hi everyone, thanks for the replies so far, the car is with a Mercedes specialist so it’s been plugged into the proper Mercedes computer they lease direct from Mercedes, since I started this thread the have done a sniff test on the coolant and there is no sign of combustion gasses present and also no coolant in the oil so fingers crossed they’re pretty confident it’s not a head gasket failure. The car is a 62 plate coupe so should be well clear of the head bolt issue as well, I think the only thing left is either a water pump not performing how it should be or a blockage in the radiator or one of the cooling gallery’s! Thanks so far,

Dan

 

[Trinitom]

95 is above normal temp

95 it's perfectly normal, these engines run hot and from 90 to 100 its normal.