According to a mechanic, one of the two fans in front of the radiator (on the outer side of the radiator) died.

He said I could wait until the failure of the other, now operating, fan.

But I do not know how I can see whether one of the fans died or not.

I just opened the hood. Both fans were not rotating. Engine temperature gauge was at 87~90 degrees C.

How can I test these fans?

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1992 300D 2.5 turbo diesel. 319 k miles.
124.128 chassis, 602.962 engine, 722.418 tranny.

The fans should come on at low speed when the AC compressor is engaged, then at high speed at engine temps above 105C or something like that.

Sixto
95 S420
87 300SDL

You can unplug the wire leads going to the fan and then run a 12v+ to one wire and a 12v- to the other and the fan should come on.

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1984 300SD 326,997 miles and counting . . . No wait, my odometer is still dead

Surprisingly no one mentioned that with everything off and cooled down:

Grasp the center outer [spool?] of the auxiliary fans, and with a rapid twist and release motion, the fan should rotate freely with no restrictions and/or dragging...

If there is binding of any sort repair/replace as necessary...

This does not apply to the engine driven belt fan...

Maybe someone would care to explain testing an engine fan...

Just trying to help thanks.

I rotated the fans with my finger. The fan on the passenger side rotates freely, but that on the driver side makes noise as if there were some leaf in the motor touching something with some period as the fan rotate.

If I drive my car with both auxilary fans dead, do I damage my car?

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1992 300D 2.5 turbo diesel. 319 k miles.
124.128 chassis, 602.962 engine, 722.418 tranny.

"...If I drive my car with both auxilary fans dead, do I damage my car..?"

In my humble opinion: "yes it is possible if you overheat the engine"...

Check out www.car-part.com to see if you can find/round-up a worthy used fan motor...

When a good fan motor is installed, find any faulty fuses/relays/switches, before you think there is something [electricaly] wrong with the electric fan motor(s)...

[because some fuse/relay/ or switch is probably burned out from the previous faulty fan motor...]

If I were you I would first remove that faulty fan motor, and see if there is some way to get it operational again... if it needs oiled or something...

Just trying to help, thanks.

I had the exact same symptoms and noise from one of the fans this week. The noise, which initially I thought could be a defective bearing, turned out to be paint peeling off from the inside of the fan shroud.

The fan would then touch the chunks of peeling paint and make the noise that you describe. I peeled off, most of the paint, and both fans now works fine.

Phil

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'95 E300 Diesel, 264,000 Miles. [Sold it]

An MB dealer diagnosed this problem. They said both fans operate normally.

On the way home however, the temperature gauge was pointing about 100 degrees C (I was driving slowly in residential area with air conditioner on). For curiosity, I stopped my car and opened the hood. Only one of the auxiliary fans was rotating. The other was completely still.

Is this normal?

At some stage, only one fan rotates? When the temperature becomes higher, then both fans rotate?

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1992 300D 2.5 turbo diesel. 319 k miles.
124.128 chassis, 602.962 engine, 722.418 tranny.

Review my post above, since I had the exact same symptoms.

The reason that at some stage both fans start working is that as your engine heats up further it engages the higher fan speed. This higher speed is strong enough to overcome any drag on the stuck fan. However it is NOT normal for only one fan to operate under any condition.

I should have also mentioned in my reply (above) that after I removed the peeling paint, I tapped the stuck fan's motor lightly with a mallet to dislodge any dirt that may have lodged inside its motor.

Its been 6 months now, and both fans have been working consistently and quietly ever since.

Phil

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'95 E300 Diesel, 264,000 Miles. [Sold it]

Thanks.

The service advisor at the MB dealer answered that the fans do not work in tandem. Oh, dealer ~

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1992 300D 2.5 turbo diesel. 319 k miles.
124.128 chassis, 602.962 engine, 722.418 tranny.

Your MB Service advisor is WRONG.

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'95 E300 Diesel, 264,000 Miles. [Sold it]

I saw the auxiliary fan circuit diagram at Alldatadiy web page.
Both fans get the same voltage in any case, which means that when one rotates, the other should also rotate.

The MB dealer was wrong.

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1992 300D 2.5 turbo diesel. 319 k miles.
124.128 chassis, 602.962 engine, 722.418 tranny.