My W210 let me down for the first time today. It was about 90F outside, a/c on, and I was stuck in traffic. I noticed my A/C wasn't blowing cold, a quick look at the dash and I saw my temp gauge up by redline! I immediately shut it off and had it towed home. Some coolant came out of the expansion tank cap but only a little after it was shut off.

Little more info:
It rises to temp at a normal speed, both upper and lower hoses feel hot onece warmed up.

The Main fan: feels fine, no wobbles, no noise. There is a slight resistance with the engine off, easily turned by hand and will spin several times. When the car is running it spins seemingly the same speed. No signs of engaging or disengaging.

The Aux fans: passenger one spins freely while engine is off little to no resistance. Drivers fan has resistance fairly stiff. When running in the driveway I got it up to ~92C, the drivers fan never moved and the passenger one spun at the same low speed from the start and never changed.

I also tried putting the key in thr #2 position and holding down both auto buttons for 10seconds but the aux fans never spun up.

Are these normal? What else can I check or should I suspect?

Thanks!
Zack

It looks like your fans need some work. Your fan clutch (for the main fan) is apparently shot and needs to be replaced. The fan should have fairly good resistance to rotation with the engine off. On my car the aux. fans seem to always spin at the same speed and they come on when the temp is approx. 90C. Other than that it could be your radiator, thermostat or water pump, but I'd start with the fans.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

The main fan clutch does seem shot, I just shut it off at operating temp and it spun for several revolutions afterwards so I will replace that tomorrow.

As far as the aux fans what is the proper method for checking them? The drivers side never turned on and the passenger one just spun at the same low speed as soon as the car was turned on....

Thanks!
Zack

Your auxiliary fan is bad.

There is a motor on the left side. The right side is driven by a belt from the left. Your belt is missing, which is why the right side is turning (due to the airflow from the mechanical fan).

To check the fan, press and hold both AUTO buttons on the climate control pushbutton unit for >10 seconds (my car takes at least 12 seconds). This demands full power from the auxiliary fan.

Matt is probably correct concerning your aux fans. Your fan clutch was probably at least partially engaged which is why there was sufficient airflow through the rad when parked to spin the aux slave fan. You'll need to confirm why your aux master is not spinning. Do the test again and hold the button for at least 15 seconds. Like Matt's, mines a little pokey when I do the test too.

You can check the fan clutch with engine at +95c by goosing it. If clutch is engaging, fan speed will NOTICABLY increase with RPM. Once you've confrimed it IS engaged, it should stop spinning when engine is turned off almost immediately. When only at normal operating temp it is freewheeling (you can stop it with your finger tips), will not increase speed with RPM and it will continue to spin a time or two when engine is shut down.

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

Good thread by Tom .... R&R Fan Clutch...

R&R of Viscous Coupled Fan, Serpentine Belt Replacement W210 E300D

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#dieselFLEET
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'97 E300
'99 E300

Well I just ordered an OEM fan clutch, auxillary fan motor with belt, and thermostat kit from Phil. I think all but the thermostat is shot, so I'll replace all those and I also have new MB coolant ready so I'll do a complete flush as well. Hopefully that will make things right again...

Also AutohouseAZ had motor mounts on sale so I ordered a pair at $110 shipped. When revved the engine would torque to the passenger side a bit so I figured they're due too.

Thats $550 all told today in parts with next day Saturday delivery... Ouch...

You will still need to determine why the aux fan is not comming on. It is either dead, or one of the controls that activates it is bad.

MattL can explain much better than I how to test that system.

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

Well 12V to the fan motor plug didn't do anything so Im guessing its shot. I hope when I get the new one all is well.

Anything else I should check or inspect/test?

Zack

Don't forget that the water pumps are a weakness on these engines.

I heard you can spin the impeller of the WP when you have the Thermostat out. I'll give that a shot when I swap the T-Stat out...

Thanks!
Zack

Hi

Yes if the impellor spins while poking your fingers through the thermostat housing then its shot.
Be careful early thermostats were part of the cover and not replaceable seperately, if yours is one of these then you need a new cover and thermostat as well.

McCool300TD

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1988 190E Sold
1996 C230K Sport Sold
His: 98 E300TD Estate, 7 seater, Avantgarde, Silver, Black cloth, parameter steering, dipping rvm, folding mirrors, rain sensing wipers, pentagon tints, 17" Elegance wheels. 298K
Hers: 93 300TD, 7 seater, Grey MB Tex pearl blue metallic, 15" 8 hole alloys, OTG, Cruise, not much else 220K

I took the viscous fan clutch off and auxillary fan assembly out tonight, as the parts should be here in the morning. My aux fan wasn;t working with 12v supplied and the "belt" was not connecting the 2 fans. I also put in a new serpentine belt I had sitting around.

Hopefully everything will go back in nice and quick tomorrow when the FedEx guy shows up

Zack

You know that the fan is bad. Hopefully the module which powers it is good. A bad fan could toast your module.

I'm not sure what module you have in your car, as there are three possibilities. Hopefully we won't have to cross that bridge when you plug in the new fan.

But a word of warning: I've heard of fans being wired in reverse. I'm not sure that OEM fans aren't affected. Put it in test mode and ensure that it is blowing the right way before you drive the car.

FedEx lady was here ~10 and brought me my parts.... The Aux fan is now working (was a quick and easy swap) The Viscous fan was swapped out easy too, no special tools needed and it now stops immediately when the car is shut off.

I'm gonna go take it for a test drive, Im also looking at a 87 300D this afternoon

I'll do the coolant flush and t-stat this afternoon as well. Hopefully things are back to good again!

Thanks Guys!
Zack