95 C280 running hotter than usual

[shawncisco]

My car has always run a little hot in the summers, in town with the A/C running, but the past week and a half it's almost into the red.
I've flushed the radiator,, replaced the coolant and added "water weter", and checked the thermostat. Don't know what else to try.
Will it hurt anything if I put a colder thermostat in. Say a 180?
Any advice would be great. thanks.

[Arthur Dalton]

Aux fans coming ON ???

[juribe2]

Some things to check:

Aux fans operation (high and low).
Coolant leaks.
Expansion tank or radiator pressure cap.
Temperature of upper and lower radiator hoses.

[msethk]

fan clutch?

[shawncisco]

Over the past few days I've changed the thermostat, cleaned the condensor (which was VERY dirty), and flushed the motor and put in a 50/50 coolant and water mixture. But today again while driving on the freeway with the a/c on it climed again to almost 120. The Aux fans seem to be coming on at about 100.
Something else I noticed was at times the car will start running kinda ruff. It's only noticable when your taking off from light to light, but when it starts running ruff, the temp starts to climb. If I shut the car of for a few seconds and restart it, it usually takes care of the ruff running, and won't get any hotter.
Don't know if this is related or not but it makes me thing that my problem could be electrical related or a sensor of some type, because I've pretty much changed out all the comon problems that cause overheating.
I've also noticed that even when the car is up around 120 the upper radiator hose dosn't always have preasure on it.

[periap]

You seem to have 2 problems - see below for discussion of low speed fan circuit - fuse blown could be an issue.

For the loss of power - there are many other posts that discuss this - basically the computer will shut down some injectors due to detecting spark knock - need to check plugs, wires, coils ect. - some hints:
1) Do Not use platinum Plugs - recommended are the original copper plugs - non-resistor if you can find them - need replacing about every 30k I am told
2) Check or replace the wires - try first the conectors from the coil directly to the plug below it.
3) Look up wiring harness issues and see if your engine wiring harness is failing - plastic will be brittle and falling apart - has been a problem on some models


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.

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