Here's what you should do:
1. Identify the problem: Is the belt slipping (squealing, especially when cold or under load)? Is it cracked, frayed, or glazed? Is a pulley damaged or misaligned? Address the *cause* of the problem, not just a symptom. A squealing belt might just need cleaning, while a cracked one needs replacing.
2. If the belt is slipping due to a worn belt: Replace the belt. This is the correct procedure. You'll need a new serpentine belt of the correct size for your 300E. Consult your owner's manual or a parts store for the proper part number. Replacing the belt involves:
* Removing the old belt: This often involves carefully maneuvering it off the pulleys; some pulleys may have a small access hole to allow the belt to be removed more easily. Consult a repair manual for specific instructions; it’s usually easier to remove it from the smallest pulley first.
* Installing the new belt: Reverse the removal process, ensuring the belt sits correctly in all the grooves of the pulleys.
3. If you suspect a pulley is damaged or misaligned: This requires a more detailed inspection. A bent or seized pulley will cause the belt to wear prematurely and slip. A misaligned pulley might also be the problem. This often requires professional attention, as correcting misalignment can be complex.
4. Check the belt routing: If the belt isn't routed correctly, it won't work properly. Consult a repair manual or diagram to ensure the routing is as per the factory specification. Getting this wrong can cause serious damage.
Important considerations:
* Repair manual: Obtain a repair manual specific to your 1991 Mercedes-Benz 300E. This will provide detailed instructions and diagrams, crucial for this job. Don't rely solely on general advice.
* Tools: You'll likely need a set of wrenches and possibly a belt tension tool (though not typically for adjusting tension on this model).
* Safety: Disconnect the negative battery terminal before starting any work. Pay attention to moving parts and avoid getting your fingers caught.
In summary: Don't try to "adjust" the belt. If it's slipping or damaged, replace it. If you have other issues, diagnose the underlying cause carefully, and consider consulting a qualified mechanic. Attempting repairs beyond your skill level can result in further damage to your vehicle.
