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Pelican Technical Article:

Drive Belts Replacement

Steve Vernon

Time:

2 hours2 hrs

Tab:

$25

Talent:

**

Tools:

17mm, 13mm socket, universal joint, 17mm, 13mm, 10mm wrench

Applicable Models:

Mercedes-Benz W123 (1977-85)

Parts Required:

Belts

Hot Tip:

Careful working around the radiator

Performance Gain:

Proper running accessories

Complementary Modification:

Coolant flush

Depending on how your vehicle was optioned will determine how many belts you have on the motor. On our W123 we have an A/C belt, power steering belts and two water pump alternator belts. Unfortunately you need to remove both the A/C and power steering belts to replace the water pump alternator belts.

You should check your drive belt every six months for wear, cracking, fraying, delaminating and drying out. If your belt shows any of these signs you should replace it. I recommend you buy two belts and always keep an extra one in the car. You don't want to be stranded on the side of the road for the lack of a spare drive belt.

You will need to remove the fan and shroud to replace the belts. Be aware that the radiator is very expensive and delicate and can be easily damaged while working around it. If you are going to be doing other work on the car and/or are worried about damaging your radiator, I recommend you remove it first. It is not a difficult job and can potentially save you a lot of money if you end up damaging it. Please see our article on radiator removal for further assistance. That being said, you certainly can remove the fan with the radiator in, but I recommend you put a piece of cardboard over it to protect it while working.

Note: some components have been moved for photographic purposes, you do not need to remove anything other than what is stated in this article.

Remember your car may have been serviced before and parts replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have so be prepared with different size sockets and wrenches.

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Never work on your vehicle if you feel the task is beyond your ability.

Our vehicle may vary slightly from yours as models do change and evolve as they grow older. If something seems different, let us know and share your info to help other users. Questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

All of the drive and accessory belts are run off of the crankshaft pulley.
Figure 1

All of the drive and accessory belts are run off of the crankshaft pulley. While some people claim they change all of their belts without removing the fan and shroud, I feel that for the same amount of time it takes to remove the fan it more than makes up for the time you will save removing, installing and adjusting the new belts (red arrow).

With the fan and shroud removed you can see the four drive or V-belts.
Figure 2

With the fan and shroud removed you can see the four drive or V-belts. The power steering belt (red arrow) is the most forward belt and must be removed to replace both the A/C compressor belt (yellow arrow) and the two water pump alternator belts (blue arrow).

Use a 13mm socket and loosen the two bolts on the right side of the power steering pump (red arrows).
Figure 3

Use a 13mm socket and loosen the two bolts on the right side of the power steering pump (red arrows). Use a universal joint on the upper bolt mounting bolt and a regular socket on the lower slider bolt, also you do not need to remove the nuts or bolts just loosen them.

Use a 13mm socket and loosen the slider nut on the left side (red arrow).
Figure 4

Use a 13mm socket and loosen the slider nut on the left side (red arrow). You may hold the bolt head on the rear of the pump.

Use a 13mm socket and working between the two upper lines completely loosen the tensioning bolt (red arrow).
Figure 5

Use a 13mm socket and working between the two upper lines completely loosen the tensioning bolt (red arrow).

You can now push down on the power steering pump and slide the belt off the pulleys (red arrow).
Figure 6

You can now push down on the power steering pump and slide the belt off the pulleys (red arrow).

To remove the A/C belt loosen the two 17mm bolts on the rear of the compressor (red arrows) from below.
Figure 7

To remove the A/C belt loosen the two 17mm bolts on the rear of the compressor (red arrows) from below.

Working from above loosen the 10mm tensioner and push the compressor in towards the crank pulley and slip the belt off.
Figure 8

Working from above loosen the 10mm tensioner and push the compressor in towards the crank pulley and slip the belt off.

The alternator bracket was designed and redesigned several times over the years but they all work on the same principle.
Figure 9

The alternator bracket was designed and redesigned several times over the years but they all work on the same principle. The main differences are found in the bracket with some having nuts welded to the bracket in the front and some in the rear. Our 1985 300TD had the lower nut welded to the front of the bracket. Begin by loosening the 17mm nut and bolt on the tensioner bracket (red arrows).

Next loosen the 17mm nut and blot on the mounting closes to the water pump pulley (red arrows).
Figure 10

Next loosen the 17mm nut and blot on the mounting closes to the water pump pulley (red arrows).

Working from below loosen the 17mm bolt (red arrow).
Figure 11

Working from below loosen the 17mm bolt (red arrow).

At this point usually you would loosen the tensioner rod on the front of the alternator but the tensioner on our project cars rod had broken off--the previous owner had just tightened everything down to keep things in place.
Figure 12

At this point usually you would loosen the tensioner rod on the front of the alternator but the tensioner on our project cars rod had broken off--the previous owner had just tightened everything down to keep things in place.

With everything loosened you can push the alternator in towards the crank pulley and slip the two belts off.
Figure 13

With everything loosened you can push the alternator in towards the crank pulley and slip the two belts off. Installation for all of the belts is the reverse of removal. Mercedes makes a special tool for measuring the tension on the belts but a good rule of thumb is to measure furthest distance between the pulleys that the belt travels on. If the distance is between 7-11 inches the belt should deflect 1/4 of an inch when pressing down firmly with your thumb, and if the distance is 12-16 inches the belt should deflect 1/2 inch.

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