Engine Overheat Please Help?!

[ddtham]

Hi fellow 202-ers,


I have the following problem with my 97 C280.

I was driving in a cold morning today (20 F) when I noticed a rocking sound (somewhat like boiling water) coming from the coolant reservoir.

I stopped the car and opened the hood and there was no leak, only the sound from the reservoir.

I drove again for 2 miles when I noticed that my engine temperature has gone up to almost 120 C from the usual 95 C.

I stopped driving and turned off the engine and waited for 5 minutes til the temperature went back to normal (I kept repeating this cycle until I got home). My cooling fans are working perfectly though.

After a while, I decided to drive it around the block again, and the same cycle happened again.

The weirdest part is, when I turned on the heater, the temperature gone back to normal immediately.

Do you think I need a radiator flush??

Please share wyour knowledge and experiences with me....

Thank you,


DDTham

[Proven Guilty]

i would flush it, and replace the thermostat since it's a simple troubleshooting step, as you were able to verify the fans.

[matt09]

I say change Thermostat.

[shandy]

As your temp. went down when you turned your heater on, I would say your main engine cooling fan is faulty, it is the one attached to the front of the engine driven by the ancillary drive belt.
The fan is driven through a viscous coupling which has probably failed, replace this and all should return to normal.

[ddtham]

Originally posted by shandy
As your temp. went down when you turned your heater on, I would say your main engine cooling fan is faulty, it is the one attached to the front of the engine driven by the ancillary drive belt.
The fan is driven through a viscous coupling which has probably failed, replace this and all should return to normal.

I'm ordering my thermostat as we speak along with spark plugs and wires to fix my other problem.

How can we tell that the viscous coupling is broken?? I remember I've read somewhere that we can just check by trying to turn the fan by hand when the engine is cold to see any resistance? Is this relevant??

Btw, when the viscous coupling is broken I just need to change the fan clutch right??

Thanks a lot in advance....

[shandy]

When your engine overheats as you describe the engine cooling fan should be running at high speed, there will be a loud roaring from the fan and a strong backdraught when you rev the engine ;there is always some slippage in the coupling as the fan is not designed to run at engine speed; if you stop the engine when really hot the fan should be very difficult to turn by hand. If this is not the case you need a new coupling which as you say is the only part required as the fan is attached to it by 3 Allen bolts.