DIY: Removal and re-installation of Viscous Coupled Fan, Serpentine Belt Replacement
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 level (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.
Discuss this DIY here.