How to Change an Hymer Mercedes OM602 Fan Belt?

If you own a Mercedes S class classic from the late 80s to 1995, it’s crucial to know about the fan belt issue that can cause breakdowns.

While it may be a service item that should be changed every 50k or so, the job of changing it is notoriously difficult and many online resources are inaccurate and it’s often neglected until it’s too late.

The online resources and manuals are misleading, leading to frustration and wasted time.

To change the fan belt, you need to remove the tensioning roller, but the bolt that fixes the top spring bracket in place is not visible. You can find it hidden deep in the engine block hole.

Access is tight, so consider removing the radiator for easier access.


To loosen the tensioning spring attached to the hydraulic damping cylinder, follow these steps.

Locate the tensioning spring that runs parallel with the hydraulic damping cylinder. You will find a nut (marked as number 3 in the picture and yellow arrow) on a bolt that is connecting the top loop of the spring to the bracket.

Removing this nut may prove difficult at first, as the whole thing may spin. This is because there is a hex bolt head (marked as number 6 in the picture and indicated with a red arrow) at the other end of the bolt, which may not be immediately visible.

However, with a little exploration, you will find that the bolt is actually a 3-inch long bolt that goes into a hole in the top corner of the engine block. The hole is around 3 inches deep, and the head of the bolt is located there. You can reach in and feel it with your fingers, and use a spanner to adjust the tension as needed.

Once you locate the hex bolt head, the removal of the front nut will be a breeze.

To release the spring tension and install the belt, insert a bar or lever into the recess on top of the spring bracket, as shown in the diagram.

The bar must be provided by you. By moving the bar left or right, you can move the spring bracket and release the tension.

Then, push the bolt back through the bracket and into its hole with a drift or any suitable tool. Use your fingers to help the bolt along the back, but do not remove it completely.

Release the tension to the point where the top spring bracket is no longer fixed in place. This will cause the spring to lose tension, and the tension pulley will drop down a few inches.

At this point, you will have enough slack to install the belt on all the pulleys. Although still a challenging job, this method works.

However, even a seasoned technician may encounter problems without precise instructions.

Don’t wait until you experience the frustration, pain, and expense of a faulty fan belt.

Related Guides:
Classic Hymer Manuals and Brochures
Tire Pressure for Hymer from 1985 to 1990
Best Tire for Classic Hymer Motorhome

It is essential that you change your fan belt if you have an old hymer. Neglecting to do so can cause the vehicle to be inefficient due to overheating, which can lead to decreased gas mileage.

Not only that, without a functioning fan belt, the engine will not properly distribute coolant from the radiator throughout the motor itself.

Staying on top of preventive maintenance like this will ensure long-term success and keep your vehicle in tip-top shape for years to come!

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