VISCO-LÜFTERKUPPLUNG: Ausbauen/Einbauen

Removal and re-installation of Viscous Coupled Fan, Serpentine Belt Replacement

There is very limited access to the bolt holding the viscous fan to the water pump pulley. In some models removal of the radiator will be required to access the bolt - - clearance is very limited and large hands are a hindrance. The job is straightforward and requires some patience as the bolt holding the visco fan to the water pump pulley is tough to remove due to poor access.

Condition: Over-heating (lack of coupling) or excessive fan noise (too much coupling) due to failure of viscous coupling mechanism and/or loss of viscous oil. My car was doing the later and I had tremendous fan noise once car had been running for just a few minutes.


Tightening values (Anziehdrehmomente):

• Visco fan/clutch bolt to water pump pulley: 45N*m
• 3 small bolts holding clutch to plastic fan assy: 10N*m

While the photos of this job show my 1999 E300D, I believe this procedure is nearly identical across the product line where the visco-fan is used. Here is photo from shop manual covering 107/124/126 cars, my W210 utilizes essentially the same procedure:

There are the two tools I had to obtain:

8mm shortie socket

Locking lever (holds water pump pulley via hole in rear)

You may be able to fabricate an alternate locking lever. Some say it’s possible to have a helper hold the water pump pulley by hand. Instead of the short 8mm socket, you might be able to use a standard hex key which most would already own, but you would not be able to re-torque the bolt to the required value during re-assembly.

Part numbers are:

• 103 589 00 40 00 (locking arm)
• 103 589 01 09 00 (shortie 8mm hex socket)

I purchased both tools from Samstag, I think it was about $40 total.

First step is to free the plastic fan shroud. There are two clips retaining the top edge that slip straight up and the bottom edge is held in place by simple tabs at the base of the radiator (picture below):

There is very limited access on my car making the removal of the bolt holding the fan to the water pump pulley quite a challenge even with the proper tools:

I could tell my car had already been apart (a bit of damage to radiator fins) to have the serpentine belt replaced (based on date code), visco fan was original part installed at factory.

My 3/8” ratchet has a fairly low profile and I barely had adequate room to get the shortie socket in place and attach the ratchet so I could loosen the bolt. I could not get enough leverage on the ratchet and ended up doing this:

I got a spark plug wrench attached to my breaker and slipped it over the end of the ratchet handle and then was able to break the bolt loose. I figured I was home free at this time. However, as the bolt starts to back out of the water pump pulley, the ratchet is moving closer to the radiator making it impossible to remove. I had to back the bolt out most of the way with two fingers and that took quite a while as the head of the bolt was dirty and very tough to turn with fingertips. Prior to re-installation, I sanded the bolt to roughen the surface making re-installation a little easier. Hiring a young child with small hands to do this part of the job would be a huge benefit and time saver!

Here is the locking hole on the rear of the water pump pulley. There are several holes, only 1 is large enough to accommodate the locking tool:

Tool in hole:

Pictures of fan/clutch:

These three screws are removed with a 5mm hex driver:

New vs. Old:

It’s obvious the design of the new unit is heftier.

Fan blade and shroud are now out of the way and access to the serpentine belt and pulleys is excellent. Grab the lever tool from car’s tool kit as it is used to pull back the plastic block so you can remove the bolt holding the heavy spring and release tension on the pulley. Since you’re this far into the job, I’d assess the age and condition of the small damper as this is another routine replacement part.

Once the heavy spring and bolt are removed, force the tensioner pulley downwards to release tension on belt and make removal/re-installation far easier:

Install fresh serpentine belt, check Owner’s Manual for pattern used on your car:

You are ready to re-assemble the visco clutch/fan assembly to the front of the water pump pulley. Just reverse your steps, no tricks required. You may have to wiggle the fan around a bit to get the long bolt back in place. I used my fingers to turn the bolt virtually all the way back in. Once the bolt was seated, I just barely had adequate clearance to use my 3/8” torque wrench and set the final torque.

My little helper holding torque wrench:

Spinning true and quiet :

Fan clutch was approximately $90. Serpentine belt was approximately $35. I selected the Gates belt as they are OES to MBz.


Don’t let the many pictures intimidate, there’s nothing complex about these two tasks - - I just like taking loads of photos when I have time. Again, the only challenging aspect of this job is removing the fan-to-water pump bolt due to minimal access.

Good luck.

My gosh, this is beautiful.
Really went wild with the camera.
Perfect for the DIY wiki page.




Thank you.

__________________
ASE Master Mechanic
asemastermechanic@juno.com

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D
1984 190D
2003 Volvo V70
2002 Honda Civic

https://www.boldegoist.com/

Thanks!!!
It's in the Wiki HERE.

__________________
Bill Wood - Retired Webmaster
My Personal Website
1998 Mercedes E430
2010 Toyota Sequoia
My Photo Albums

EXCELLENT writeup!

How many miles on your car?

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2005 Pathfinder LE
2001 E55
1998 M3
1982 320i

Thanks, guys. My pleasure.The 1999 diesel has 60k miles.

Some folks have asked for a detailed description of the lever tool with a few measurements. I'll check and report back.

__________________
1998 W210 diesel (wiped out by a texter)
Baum spring compressor "for rent"

here are basic measurements for lever tool:

Attached Thumbnails

   

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1998 W210 diesel (wiped out by a texter)
Baum spring compressor "for rent"

Here's my experience doing it on a 602 -

"I just put a new fan clutch in my 1992 300D 2.5 Turbo (has a OM602.962 engine). I followed the instructions at
http://www.peachparts.com/shopforum/showthread.php?t=158069

Those instructions are for a E300D, but basically they are the same and very helpful, with the following caveats and tips.

1. You don't need a special tool to lock the waterpump flywheel so you can tighten the fan bolt on. A small hex Allen key (is that what they're called in the US?) fits in the hole just fine.

2. There is a lot more space with the 300D than there is for the car in the instructions above, so a shortened 8mm socket is not needed.

3. I found it easiest to undo the 3 bolts holding the fan on the clutch and take the fan out. Lots more space to get in there. Not sure it helps massively overall, but if you're having trouble getting in there and getting it done, consider removing the fan, it's easy.

4. Get the 606 fan clutch - much cheaper than the 602 fan and is the same, as far as anybody can tell - fits straight onto the 602 and has the same engagement temperature. I got mine for less than $80 with delivery on ebay.

While you're in there, you may as well replace the serpentine belt. It's easy. The only thing that takes a little thinking is getting the belt tightening system figured out. What you do is undo the nut holding the spring on. Then use a lever to release the tension (there's a hold in the black plastic mount that allows you to do this easily) and take the spring off. Then it is easy to put the new belt on and put the spiring back. "

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1983 240D Silver/Blue "Sadie", unknown miles. 100k miles on WVO single tank, converted to 2 tank about 10k miles ago, FPHE, Injector Heaters, Aux Fuel pump. Alcohol/Water injection. Frantz oil bypass filter
1992 300D 2.5 Turbo Green/Tan "Jade" 267K miles Stock.
1992 300D 2.5 tan/tan "Rocky" on 2 tank WVO. Pressure actuated Turbo "rat's nest" surgery completed. 197k miles

I just did my 1995 E300 diesel today. Took me 45 minutes using your wonderful article. After reading and looking at the pics I knew what to do. I used a hex key and a cheater pipe to remove and replace the hex bolt. Didn't torque it but its real snug! I used a small c clamp on the water pump and belt combination to secure it to loosen and tighten the 8mm hex bolt. Worked very nicely and cost 1.99 at Harbor freight.

You have a flair for techical writing and technical photos. I am in your debt.

Ernie in Louisville

My service manual (alldatadiy) lists the torques as:

- Fan to Viscous coupling: 100 Nm
- Viscous coupling to pulley: 455 Nm

Those sound pretty high to me but the 45 Nm that is listed in the first post sound pretty low.

Can anyone clarify this one? I recall that I torqued mine to around 90 Nm when I changed it last year as that value 'felt' about right.

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Scott C.

2006 E320 CDI (120k miles)
FOR SALE: 1998 E300 Turbo Diesel - Black w/Tan Leather - Euro delivery (236k miles)

The Mercedes Star service DVD states 45 Nm for the bolt on the viscous to pulley

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1999 E300 TD 190,000
1996 Passat TDI 225,000-sold
1996 E300 120,000-sold
1998 Jetta TDI 186,000 -sold
1983 Chev Suburban C20 6.2-sold

I was about to do a fan clutch replace job in hopes to get rid of the noise that was comming from that area. I knew the job was a fight one and have done it before. Now I dont have to worry about the problem since my fan actually has decided to detach itself from the engine. Yep, the fan, the clutch and the fan pulley are all detached from the front of the engine block and just sitting between the radiator and the engine. How does this happen? What came apart and how do I reattach this mess? I was driving and then all the idiot lights came on and i lost Power steerring, so I knew I lost the belt. I got home and found the belt in one piece. It just slipped off the pulley and let the whole mess go slack when the fan came off the engine. great. please help

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Christopher Henkel
1990 190E 2.6 - Arctic white SOLD
1986 190E-16v - Blauswartze
1993 300CE - SOLD
2003 W208 CLK 320 Cabriolet - Magma Red

A picture would help.

the center bolt on the fan clutch must have let loose, the clutch blew up or the WP blew up.....

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Terry Allison
N. Calif. & Boca Chica, Panama

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