C280 Overheating
 

MY 96 C280 w202 w/145k mi is overheating (in the red zone @ ~120+). The fans are kicking on. when it reaches ~100-degrees so I think those are OK.

The water pump and thermostat were replaced @ ~90k miles
The head gasket et all (incl radiator flush) was done ~112k miles.

I believe the radiator is original but i am not 100% sure.

Any idea where I should start to investigate?

Thanks.

more details....
 

the fans spool up in speed as the temp increases to 120 - at which point i think they're pretty well maxed out.

the radiator looks really good - only about 1-2sq inches if bent blades that i can see. it also looks pretty 'clean' (not a lot of bugs, dirt, etc in it).

i just had the car serviced and the invoice says the coolant is "OK: -20deg farenheit"... not sure if that is in tolerence.

the overheating started , odd enough, when i just got it washed - hand wash, low pressure hoses or course. ;)

it seemed to be running higher than usual after the wash but i figured it was because they let it run while washing it (85-degree ambient temp, black car)

after the wash i went to get the tires balanced & rotated and when the tech came back from the test drive i noticed green fluid boiling out from under the hood. it's all coming from the overflow - there are no other leaks in the system

i just let it cool to 60-degrees then let it idle w/the ac on while watching the temp gague. it ran up to 115-degrees and leveled off with the fans fully screaming to cool her down.

I think its time for you to check that thermostat again.

Is the hose connecting the radiator to the water pump getting hot at all ? If not, then the coolant is not circulating. If yes, then it is not removing the heat, perhaps a clog in the radiator somewhere ? I would flush the radiator no matter what. Are the aux fans turning in the correct direction ? Lately, there have been several posts where the main problem was that the aux fans were turning in the opposite direction. They should move the air from the outside to the inside of the engine compartment. Take a small piece of newspaper and hold it near the front of the fans, the paper should be sucked in and not blown away. Someone also mentioned on another post, that these fans have markings for direction of rotation.

had the same problem with mine... spent a few bucks to check the easy things. flushed the radiator. filed it up with new mb antifreeze. new thermostat. no problems since. Replaced the fanclutch first but i probably didnt need to, although it may be an issue to look at.

I agree.... that is where to start....and if it is a Wahler , change it to Behr.

Thermo!
 

Yet - thermostat. The dealer wanted $122 just to diagnose the problem. They said if it was the thermo it'd be at least 1hr labor plus parts. Total would be at least $250. I put a new thermostat in in less than 10 minutes. Under $40. I can't thank y'all enough for the advice.

Is it a reasonably easy thing to flush & fill this car d.i.y? Or should I leave that to the pros? I'd like to take care of it just to make sure it's done now that everything seems good.

Here are a couple of threads on the procedure for that car:

http://www.peachparts.com/shopforum/showthread.php?t=59042

http://www.peachparts.com/shopforum/showthread.php?t=35507

Arthur, what is the difference between those 2? Also, is there a "normal life" for Thermostat's? Mine is about 9 years old. Do they normally fail hot or cold or is it random?

Thanks,

Mike

The difference is quality...Behr also have a better flow rate by design.

.and a thermo can fail in many ways, but the most often is they open late as they age.

A good quality A/F mix helps the longevity of all coolant components.

:book: Hi everyone! Just an update - I have a 1995 C280 with only 63k miles and have been having the same coolant temp problems since I purchased the car a year ago. I went through all of the normal updates: new thermostat, flush and drain, even purchased from JimF the "cool harness" - but the real symptom never changed.

:) There was another post where someone mentioned that in the low speed fan circuit for his 1994 C220 - there was a relay that controled this circuit in the section "behind" the fuse box on the drivers side of the engine compartment. This relay has a "piggy-back" fuse installed at the factory as a 15A fuse. The indication was that the fans draw over 20A at times and that a 25A or 30A fuse should be placed here.

:D When I looked - that was my problem - a simple fuse replacement would have solved the problem.

Here are the symptoms:
1) At some temp the low speed fan circuit should turn on the fans and they should run continuously until the temp gets low enough to turn them off - or - the high speed circuit kicks in.
2) If your fans only turn on and of in high speed and typically stay on only for 20 seconds or so until extreme high temps are reached (110-120 degrees C) and you never see a slow speed fan condition. CHECK THIS FUSE
3) Most of the time the temp stays between 85-95 degrees C when operating at speeds of 30 MPH or more, but then in stop and go traffic - or low speed driving - temps can move up to over 100 degrees C and stay there until "something changes" (no clear indication of what made the temp go down). CHECK THIS FUSE

<1) At some temp the low speed fan circuit should turn on the fans and they should run continuously until the temp gets low enough to turn them off - or - the high speed circuit kicks in.
>

Low fan is the diagnosis, but Low speed fan has nothing to do with temp sensing.. It is turned on by the a/c high-side presure switch when the a/c system is being used.
It will passively effect coolant temps , but it is a completely different system than the cooolant temp sensed high fan circuit .
The fuse uprade is correct.
If the fuse is OK, The most common fault of no low fan is low refrigerant level, where the high side pressure does not attain sw. cut-in pressure spec for low fan relay activation.

c280 overheating
 

The only suspect in my car is the water pump, after checking all other cooling components and replacing faulty ones. How can I verify that the pump is pumping correctly? Thanks

So in your picture it is the Blue relay that should have the 25 amp fuse instead of the 15?

Not trying to scare you but have you looked into the head gasket,Look for engine leaks if you have tried all suggestions above think about the piston pressurizing the water system I would have it checked out as I would think after doing all that and you did have the head gasket replaced I would look for small engine leak.