Help! I have a 93 300E 2.8L that keeps overheating. I have recently replaced the radiator, radiator cap, thermostat and the "Infamous water tee" that busted. I have also completely flushed the system and refilled with 60/40% G05 & water. I drove the car for a week after doing all this and even went out of town; everything was going just fine until this morning when it overheated again. The car has dual cooling fans but in the two years I've had the car only the left fan works and has been able to keep the system cool. The fan clutch is good. The fins in the water pump look good also. Does anyone have any ideas?

Pull the connector off the blu sensor at thermo housing w/key On and see if you have high fan

..and you should have both fans working, for starters,

__________________
A Dalton

I have pulled the connector off the blue sensor at thermo housing w/key on and the one working fan does come on.

I am working on getting a replacement fan for the one that has never worked. I found a place in Memphis: Wiley Imports, 3763 Old Getwell Road, Memphis, TN 38118 (901)362-3081 that "specializes exclusively in Mercedes-Benz Parts, Service and Salvage for over 30 years." They have been a great help so far.

OK...Good.

Spin the other fan by hand to make sure it is not bound up..

Test #2:

Over at the reciever/drier, there is a sw with a 6" wire pigtail on it..pull the insulating sleeves back to expose the spade connectors at the pigtail and jumper those two wires w/key ON
Should have a LOW fans/fans..

__________________
A Dalton

The have already spun the non-working fan and it does spin freely.
I have not tried Test#2 yet. I will try that and let you know what I come up with.

Very Good
With the blu sensor unplugged and the other fan running, give the broken fan a smack with a rubber hammer from the center of fan hub [ not hard]..the brushes simetimes hang up...

__________________
A Dalton

We got the other fan working. A few good wacks and some trash fell out and it started working. After we got it working we drove it for about 10 minutes and it started overheating again. Another mechanic I work with said is could be the fan clutch and that the fan is a little slow. This is really the only thing that I can think of unless I didn't get a good enough look at the fins in the water pump. This is driving us crazy...What else could be happening to cause the overheating?

Does it o-heat with a/c OFF?
That is why I have the next test as low fan jumper.

__________________
A Dalton

Yes it does o/h with a/c off.
Did not get to low fan jumper test but will try after work and report back.
Thanks for all your help so far.

< <<


OK

What does the temp gauge say??

__________________
A Dalton

It gets up to just below 120. After we turn the engine off, let it set for about 10 minutes, we can crank it up again...at idle it goes up between 80 & 90 and pretty much stays there, but after driving about 10 minutes or less it starts heading up to 120.

<>

.and the high fans come ON ??? [ at about 105 ?]

__________________
A Dalton

Usually the high fans come on within seconds of turning on the a/c.

No

That is low fans.

That is why we want test #2.

Anyway, the HIGH fans come on at 105C...that is the blu sensor I had you pull the connector off..so....if the high fan does NOT come on when you see 105C, we have a BAD sensor...see where I am going here and why I need the results of each test.
My test are sequenced and the next one depends on your YES/NO answer to the last one.

So, do the high fans come on when you see 105C ?...yes/no

__________________
A Dalton

Gotcha! Sorry about the mix up.
I'll be back at home in a couple of hours. I'll try test #2 then and get back to you.