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Old 03-12-2013, 11:08 AM
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Join Date: Jan 2011
Posts: 4
w115 220D Auxilary fan is grinding... can bearing be lubed?

The bearing inside of the auxiliary fan on my w115 220D is grinding. When I turn off the car, the fan continues to spin for a little while and has this bad grinding sound. (sort of sound like a circular saw slowing down). I tried to move it with my hand and something is totally grinding in it somewhere. I can also hear it when I go under a freeway overpass. My car is a little odd as I noticed that the aux fan is always on, so Iím assuming itís jumped somewhere, or the clutch (if there is one) has seized up...

My question is if there is any way that this bearing can be lubed or replaced? I would rather keep the OG MB fan assembly in there if I can!

I checked all over the net, and here, and could not find any good instructions about how to take this fan assembly apart.

The manual references the aux fan clutch and states that it cannot be repaired, and that it should be replaced, but I am not even sure I can see any aux fan clutch. Is the clutch inside of the fan or perhaps behind the fan pulley or something?

Thanks in advance for any adviceÖ

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Old 03-12-2013, 12:34 PM
Join Date: Sep 2005
Posts: 664
There is no clutch. The fan is either off or on.

Many of these are wired into the A/C system with the theory being that the only time you would ever need it is when the A/C system is running. There is a high-pressure switch on your A/C dryer/filter that has a 12V line running in and, when the system is turned on and the pressure in the dryer comes up, senses the increased pressure and completes the circuit, thus turning the aux fan on.

Mind you... This is how is is supposed to work. I have also seen them wired up to be hot all the time with the ground wire hooked up to the pressure switch, and I have also seen the pressure switch bypassed. Owners do this under the theory that if some cooling is good then more cooling is better. It is also a lot cheaper to just bypass the switch than it is to replace it when it goes bad which, like anything mechanical, it will.

The fan cannot be repaired, but there is really no sense in doing so since they are so easy to replace and so easy to find used. I probably have one or two of them laying around I could sell you cheap, or you could check out Ebay. I always have replaced them frame and all since this is the quickest and easiest way to swap one out.

By the way... The aux fan was an option when the 220/8 bodies first appeared, but it soon became obvious that it was necessary with the factory A/C system so it just became a part of the A/C package. The whole 'option' thing did not last but a few months. The bottom line on this is that there are a lot of these fans floating around out there used and in very workable condition, so there is really no need to repair the one you have.

I would not hesitate on fixing this. Summer is coming up and you will need the aux fan to keep the engine temp down even if you are driving around without the A/C operating.
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Old 03-12-2013, 02:13 PM
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Join Date: Aug 2002
Location: near Scranton, PA
Posts: 5,178
The primary fan is mechanical and has a clutch. The aux fan is electric and has no clutch. Neither are really serviceable parts.
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Old 03-12-2013, 02:35 PM
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Join Date: Jan 2011
Posts: 4
So what I thought was the aux fan is actually the primary fan. Iím really sorry about that. You helped me figure out that my car does not have an aux fan, but I think I will try to find one to install when I get the AC working this summer.

Iím guessing the solution is to replace the primary fanís clutch to stop the grinding?

is there anything else that could be causing this noise?

AND...does this mean that my primary fan is jumped somwhere to always be on?
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Old 03-12-2013, 03:44 PM
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Join Date: May 2010
Posts: 798
The auxiliary fan is in front of the radiator--the primary fan and clutch are behind the radiator.

If your car is equipped with air-conditioning components it's possible that the pulley which tensions the AC belt is rubbing against the primary-fan pulley--if so the AC pulley needs to be moved outward and fastened with its central allen-head bolt

Tim Kraakevik
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Old 03-12-2013, 04:08 PM
Join Date: Sep 2005
Posts: 664
The primary fan, the one that is bolted to the fan clutch that is bolted to the water pump, is also easy to change. It is time consuming, but what repair on a Mercedes is not?

You can also find this clutch, which is what wears out on the primary fan, on Ebay for far less than a one new. They are all about the same; just make sure you get one with the same bolt pattern (where the fan itself bolts to the fan clutch) as there was a change in there somewhere.

And the adjustment pulley that was mentioned.... You might consider changing this as long as you are in there. These are cheap and they do wear out, so it is best to go preventive on this part.

No need to change the entire assembly. The pulley itself is sold as a stand alone part. And you should consider changing the pulley 'bolt', too, since these can start to wear after 20 years or so.
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Old 03-12-2013, 05:54 PM
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Join Date: Jan 2006
Location: Tucson, AZ
Posts: 4,551
One of the first things I did when I had a 220D was to eliminate the fan clutch assembly. I used only the electric fan. I drove it for years here in the desert with no problems.

Both my 250C and 280C use only an electric fan.
ďWhatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.Ē
― Brian P. Cleary, You Oughta Know By Now
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Old 03-13-2013, 03:21 PM
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Join Date: Mar 2006
Location: Atlanta, GA
Posts: 121
Bearing in the Aux Fan

The electric aux fan on my 1970 300SEL was grinding/growling. The fan and motor come apart very easily. There is a small ball bearing on the front of the motor. I measured the bearing and was able to find a replacement from a bearing supply house. It was one of the easiest things i ever fixed on my car.

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