The M117 engine in 5.6-liter form (1986-1991) has a total of five (5) v-belts that drive the operation of several key engine systems, including the water pump, power steering pump, alternator, air-conditioning compressor, and the "smog" (air injection) pump. One belt couples each of these systems, with the exception of a dual-belt set of pulleys that drive the power steering and water pump.
It is vitally important -- particularly for the alternator and power steering+water pump belts -- that the belts be in a good condition and free of cracks or other wear. These belts should be checked annually for cracks, fraying, and glazing on the friction surfaces that run against the pulleys for these systems. A good rule of thumb is that the belts should be replaced every few years, and around every 30,000 miles. Of course, hotter climates can cause rubber items of all types to wear faster, so it's important to keep a regular eye on all five of these belts.
My own 1989 560SEC last had its belts replaced in October 2009, when the car had 180,000 miles on the odometer. The critical alternator v-belt suffered a failure in May, 2011 (alabbasi will remember this situation well), and was replaced at that time with a new Gates belt. However, the majority of the belts had gone more than 56,000 miles, which is probably way more than they should have gone.
Recently, in some wet Houston early-spring weather where I was driving through puddles, I noticed a squealing belt. That evening, I checked the condition of all of the belts, and noticed that several of them had visual cracks that I could see with a flashlight. Seeing that I had a complete set of Continental replacement belts on hand, in my parts stock, I resolved to change the belts sooner than later.
This job is a medium DIY job, and about a 4 on a scale of 1-10 in difficulty. It only requires hand tools to accomplish, but does require a few hours and some expertise to accomplish. A "helper" can be a good thing to have for certain points in the job, but it can be done alone. For a first-timer, I would budget around 3-4 hours for this job. More experienced mechanics can probably do it in around 1.5-2 hours.
MB factory belts are highly recommended, although quality aftermarket belts (such as those from Conti) are certainly fine. I have seen a deterioration in recent years in Continental rubber products (brand name CRP), and have had others tell me that Gates (made in USA) belts are very good quality. However, I do not believe that the Gates belts fit on the MB pulleys quite as well as the Conti and MB factory belts do.
- Alternator belt: 009 997 53 92 or Conti/CRP 10X1005
- Air-conditioning compressor belt: 004 997 05 92 orConti/CRP 13X960
- Power steering & water pump belts (2 required): 005 997 95 92 (set of two belts) or Conti/CRP 10X1110
- Air injection pump belt: 006 997 24 92 or Conti/CRP 10X750
- Flat-blade screwdriver, medium
- Assorted combination wrenches - 10mm, 12mm, 13mm, 17mm, 18mm, 19mm, 21mm
- Assorted 1/4" or 3.8" drive sockets and extensions - 10mm, 12mm, 13mm, 17mm
- Magnetic pickup tool
- Medium-size Crescent wrench
- Ramps (or jack) to elevate the car -- not required but makes the job MUCH easier
- Rag (to catch coolant drips)
Getting started, I lay out the new belts, so you can see what they look like close-up.
IMG_7192.JPG IMG_7193.JPG IMG_7194.JPG IMG_7195.JPG IMG_7196.JPG
And, for emergency purposes, to avoid being stranded, I keep a spare alternator belt in my spare tire bucket. I should probably add a couple of power steering+water pump belts as well. These three belts are critical to the operation of the car.
NOTE: If the alternator belt breaks, and the battery is in decent condition, it is possible to drive the car "on the battery" for a good 50+ miles, as long as one doesn't use any electrical items, such as headlights, ACC fan, and so forth. If the PS+water pump belts break (luckily there are two, for redundancy), you are pretty much dead in the water and should NOT run the engine any further. It is possible to "limp home" with one of these belts working, however. The alternator belt generally can be replaced in about 15 minutes with the tools found in the emergency tool kit; the PS+water pump belts require more tools that most folks would not carry in the car with them.
Getting into the job, here are a few views of the belts as seen from the top, underhood. As you face the car, the first photo is from top center; the second photo is from top left; and the third photo is from top right. The fourth photo is taken from beneath the car.
IMG_7199.JPG IMG_7200.JPG IMG_7201.jpg IMG_7202.jpg IMG_7203.jpg
As you get started, to give yourself enough room, remove both of the plastic air intake pipes (or single pipe, if you have a 560SL, or 420SEL M116 engine).
The first component to the job (which I didn't do until well into the job), is to remove the fan/fan clutch assembly, and also the plastic fan housing. The fan is held to the hub of the water pump by four 10mm bolts. It's a good idea to soak each of these bolts with a quick shot of PB Blaster or WD-40 or other solvent to help facilitate their loosening.
After letting them soak for 5 minutes or so, take a 10mm box-end wrench and loosen them in a counter-clockwise direction. The hub MAY slip a bit, so you can apply downward pressure on the two PS+water pump belts with your free hand as you loosen each bolt.
After loosening the bolts and removing them from the hub and pulley, remove the two metal spring-clips that hold the plastic fan shroud to the radiator core support. After doing this, CAREFULLY remove the fan/clutch assembly upward and a bit to the side, being VERY careful not to ding any of the cooling fins on the back-side of the radiator with the fan blades. With a little bit of working, the fan will come out upward.
IMG_7293.JPG IMG_7294.JPG IMG_7289.JPG IMG_7288.JPG
Then, with a flat-blade screwdriver (or Phillips head, depending on your ring clamp), loosen the ring clamp that holds the upper radiator hose to the radiator. Remove the end of the hose from the radiator, and bend it upward. You may lose a few drops of coolant out of the end of the hose/radiator, so you may want to place a rag beneath the area to catch any drops of coolant that escape.
Holding the hose upward, with your other hand, remove the fan shroud upward and out of the vehicle. Bend the hose out of the way so that it clears the upper edge of the fan shroud as you lift it out of the car. After removing the fan shroud from the car, press the end of the hose back onto the radiator, but you don't need to tighten the clamp.
After doing this, you now have PLENTY of room to work in getting the belts off of their pulleys. Technically you can get three of the five belts removed from the car without removing the fan/clutch assembly, but the two PS+water pump bents cannot go around the fan, because the fan is too large a diameter for the belts. Thus, it's best and easiest to remove the fan to remove the old and install the new belts.
The first belt you want to remove is the smog pump belt. There are two (actually, three) bolts that you want to loosen so that you can adjust the smog pump downward so that the belt can be slipped off of its pulley. The first bolt is a 5mm Allen bolt, which you can see at the center of the photo below. It is the pivot point bolt for the smog pump. You can see the dark Allen key inserted into the pivot bolt hole at the center of the photo.
Next you need to loosen the adjuster bolt(s). This is a two-piece bolt that requires loosening the inner (smaller, 13mm) tightening bolt first, and then the larger-diameter adjuster (19mm) bolt that runs up and down the toothed track. In the photos below, you can see the sequence of loosening both of these bolts. In the last photo below, the larger bolt is moved with the wrench to the end of the adjusting track, so that it provides enough slack to slip the belt off of the pulley.
IMG_7204.jpg IMG_7205.jpg IMG_7207.jpg IMG_7208.JPG
Here is the process of slipping the smog pump belt off of its pulley, and removing it from underneath the vehicle.
IMG_7209.jpg IMG_7210.jpg IMG_7211.jpg
Here are a few views of the smog pump belt, as I inspected it after removal. As you can see, there was significant cracking and deterioration of the belt. It was more than due for replacement.
IMG_7212.JPG IMG_7213.JPG IMG_7214.JPG
And, the old smog pump belt is put next to its replacement.
Next belt to remove, is the alternator belt. This belt can only be removed AFTER the smog pump belt is removed. To loosen the alternator to provide enough slack to slip it off its pulley, three bolts must be loosened. These three bolts are located on the alternator bracket, and below the alternator at the adjustment channel.
The following sequence of photos details the loosening (not removal) of these bolts. Two of the bolts are pivot bolts, and the third one is an adjustment bolt. A 13mm socket and 13mm combination wrench are required for a couple of these bolts, working in concert. Move the adjustment bolt down its channel all the way, after loosening, to create enough slack so that the belt can be removed from the alternator pulley.
IMG_7218.JPG IMG_7219.jpg IMG_7220.JPG IMG_7221.JPG IMG_7222.JPG IMG_7223.JPG IMG_7224.JPG
Removing the belt from the alternator pulley. Slip it off the alternator, and then from the crankshaft pulley. Slide it out from above.
The condition of the alternator belt, which was 1.5 years newer than the other belts, speaks for itself.
IMG_7240.JPG IMG_7241.JPG IMG_7242.JPG IMG_7243.JPG IMG_7244.jpg
Two belts down, three to go at this point.
Next up is the A/C compressor belt. This is probably the easiest of the belts to remove. All you have to do is take an 18mm box-end wrench and loosen the single bolt that tightens the belt tensioner roller to the engine block. This can be done from above. See the sequence below. After loosening, the roller drops down and easily puts enough slack to remove the A/C compressor belt.
And a few photos whilst inspecting the A/C compressor belt. Again, was in dire need of replacement.
IMG_7232.JPG IMG_7234.JPG IMG_7235.JPG IMG_7237.JPG
CONTINUED IN NEXT POST