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Thread: HOW-TO: Replacing M117 V-belts

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    HOW-TO: Replacing M117 V-belts

    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.

    Part numbers:

    • 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


    Tools required:

    • 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.
    IMG_7197.JPG IMG_7198.JPG


    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).
    IMG_7298.jpg IMG_7297.jpg


    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.
    IMG_7295.jpg


    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.
    IMG_7296.jpg


    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.
    IMG_7291.JPG


    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.
    IMG_7206.JPG


    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.
    IMG_7216.jpg


    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.
    IMG_7225.JPG IMG_7238.jpg


    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.
    IMG_7230.jpg IMG_7231.jpg


    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

  2. #2
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    Re: HOW-TO: Replacing M117 V-belts

    Now, the last two belts need to be removed -- the dual power steering + water pump belts.

    To do these, you need to loosen the three bolts that hold the power steering pump to its bracket on the front of the driver's side cylinder head. I actually REMOVED the bottom-most bolt, so that I could get the maximum slack on the pulleys. These are fairly difficult to remove, and there are two of them, so getting max slack is of the utmost importance. You can also assist and get even more slack by using a 6mm Allen key on the power steering pump adjuster, which is at the right-most edge of the backing plate, just behind a jumble of vacuum and electrical lines that are zip-tied to the backing plate itself.

    On my car, the area was fairly dirty after 55,000 miles of driving on it since the top-end rebuild I did back in March/April of 2010. So, I used a shot of brake cleaner to clean up the PS pump area, to expose the bolts so that I could get a proper grip on them to loosen them.
    IMG_7226.JPG IMG_7227.JPG IMG_7229.JPG IMG_7228.JPG


    After loosening the three power steering pump bolts, and the adjuster to its limit, with some effort you can slip the belts off of the pulleys, and then lift them out of the car. In my case, both belts were in decent condition and didn't have cracks or other obvious wear.

    Now, its time to replace the belts. Start with the two power steering + water pump belts ...
    IMG_7261.JPG IMG_7262.JPG


    You are going to have an issue with getting the belts back onto the pulleys, so this procedure is advised. First, put both belts in their crankshaft and power steering pump pulleys. Then, take the small black water pump pulley (that you previously removed from the car when you removed the two belts) and place the belts in the grooves of that pulley. Then, WORK THE WATER PUMP PULLEY SLOWLY ONTO THE WATER PUMP HUB in an angled, back and forth motion, until it lines up and slips onto the end of the water pump hub. See the photo below for this process in action.
    IMG_7263.JPG


    When this process is complete, the belts will be straight and you will feel the pulley slip into place on the end of the hub. BUT .. you're not done yet. You need to do one very important step .. you need to line up the holes in the pulley for the 10mm bolts, with the holes in the water pump hub. There's a 99.9% chance that when you slip the pulley onto the hub, that the holes don't line up so that you can insert one of the 10mm bolts to hold it into position.

    Per the photo below, what I did was to take a small, jeweler's screwdriver and stick it through a hole in the pulley. Then, using a manual, ratcheting motion, I moved the hub with the end of the screwdriver until the screwdriver "found" the hole in the end of the hub. Then, I inserted a 10mm bolt into the hole to hold everything in place until it was time to replace the fan on the pulley/hub.
    IMG_7264.JPG


    The following are photos of replacing the remaining belts on the pulleys, basically in the reverse order of how they were removed.
    IMG_7265.jpg IMG_7266.jpg IMG_7267.jpg IMG_7268.jpg IMG_7269.jpg IMG_7270.JPG IMG_7271.JPG IMG_7272.JPG IMG_7273.JPG IMG_7274.JPG IMG_7275.JPG


    The rest of the job is basically tightening up and adjusting the pulleys and belts. For the A/C pulley tensioner, you need a medium sized Crescent wrench, which you insert onto a flat spot on the pulley arm, and lift up with one hand. With your other hand, you tighten the 18mm bolt that affixes the tensioner to the engine block.
    IMG_7282.JPG


    Insert the fan and shroud together as a single unit (fan loosely fitted INSIDE the shroud) down into the area behind the radiator. You'll need to pull the upper radiator hose off of the radiator temporarily to fit this assembly back down into place.

    Note that there are two tabs at the bottom of the radiator lower support that the shroud fits into, so you'll want to check from below that these tabs are engaged correctly. Clip the shroud back into place, and re-install the upper radiator hose and tighten its clamp into place.
    IMG_7292.JPG IMG_7290.JPG


    Once everything is buttoned down and adjusted back in place, you need to measure the tension of the individual belts. To do this, it's best to use a "Krik-it" belt tension gauge from Gates. These are available very very inexpensively from most common auto parts houses, such as O'Reilly Auto Parts or NAPA. They take a bit of use to master, but once you get the hang of it they are easy to use. If the belts need any adjustment per factory spec, then you'll need to make adjustments with the loosening/tightening sequence as described above to provide the necessary tension.
    IMG_7280.JPG IMG_7281.JPG

    The factory MB tension specs for each belt is listed in the table below. The KG is the reading as found on the Krik-it device.

    Belt
    Tension (new belt)
    Tension (used belt)
    Alternator 35 KG 30-35 KG
    A/C compressor 50 KG 40-45 KG
    Smog pump 30 KG 20-25 KG
    PS + water pump (2 belts) 30 KG 20-25 KG

    Lastly, while you're rooting around underneath the car, be on the lookout for issues that may pop up. Be proactive and observant about what's going on with your car !! I found several issues in my inspection, as shown in the following photos:

    a) cracked smog pump hoses, which I'll put on my next order to MB
    IMG_7285.jpg IMG_7286.jpg

    b) cracked front lower control arm ball joint boots, which will in the near term require replacement of these ball joints. I've already ordered new Lemforder ball joints. You can see that some lubrication has already seeped out in the immediate area of the ball joints. Once the boots are breached/cracked, you can assume the ball joint must be replaced. Don't try to Band-Aid it with new boots. The ball joints are very inexpensive to buy new, but do require a special tool to properly install.
    IMG_7256.jpg IMG_7257.jpg IMG_7276.jpg

    c) an original fan clutch. This dates from 1985, so it's in need of replacement even though it has done a good job of keeping the engine cool. I already have a new Behr fan clutch on order. Luckily, they only cost about 20% of what a 500E fan clutch costs. Still, 31 years of service is more than enough to ask of this ol' girl.....
    IMG_7246.JPG IMG_7247.JPG IMG_7248.JPG IMG_7249.JPG IMG_7250.JPG


    Fortunately, the lower control arm bushings, where they attach to the suspension mounting point on the bottom of the car, appear to be in decent condition.
    IMG_7260.jpg

    And that is about the extent of this job.

    I hope those of you who need it, found this HOW-TO to be useful.

    Cheers,
    Gerry

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  4. #3
    E500E Guru nocfn's Avatar
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    Re: HOW-TO: Replacing M117 V-belts

    Good post GVZ. Since you are down there, for the person doing the how to should also inspect the transmission cooler lines for the same signs of age-related deterioration. Most likely original and is inexpensive insurance for a critical component for less than $25. PN 0199978082 2 required
    Last edited by nocfn; 03-16-2016 at 07:13 AM. Reason: adder cooler line P/N and cost at Desert retailer
    1994 E500
    249/275 - 8F19 or 8F32 or 8320

    1991 560 SEC
    199/268
    2014 E350 Cab 799/264

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    Re: HOW-TO: Replacing M117 V-belts

    Did this job today. Took me about five hours when including lunch.
    Thanks for the write up Gerry.
    I would use a piece of cardboard to guard the radiator from damage when removing fan.

    Would take about two hours next time.
    Last edited by Trae; 04-11-2018 at 08:33 AM.
    Trae
    1992 500E Renntech
    1993 500E
    1990 560SEC/ 2001 SL500
    1991 560SEC ECE/1995 E320 Cabriolet

  7. #5
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    Re: HOW-TO: Replacing M117 V-belts

    Quote Originally Posted by Trae View Post
    Did this job today. Took me about five hours when including lunch.
    Thanks for the write up Gerry.
    I would use a piece of cardboard to guard the radiator from damage when removing fan.
    Did you round off those bolts on the fan?
    1994 E500
    249/275 - 8F19 or 8F32 or 8320

    1991 560 SEC
    199/268
    2014 E350 Cab 799/264

  8. #6
    E500E Guru Trae's Avatar
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    Re: HOW-TO: Replacing M117 V-belts

    The bolts were not on too tightly, so they came off nicely
    Trae
    1992 500E Renntech
    1993 500E
    1990 560SEC/ 2001 SL500
    1991 560SEC ECE/1995 E320 Cabriolet

  9. #7
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    Re: HOW-TO: Replacing M117 V-belts

    Fan bolts shouldn't be too much of a problem. I've never had any issues.

    Coincidentally, I just ordered a new complete set of five Conti V-belts from Amazon for my parts shelves. It will probably be some years before new belts are required, but it's nice to have them on hand. I will keep spare alternator and power steering/water pump belts in the trunk, in case of emergency, along with a spare fuel pump relay.

    Alternator belt is super important, as it's a single point of failure. It's less likely that a power steering+water pump belt will go, as there are two of them on the same pulley.

    As I mentioned in the first post, as long as you don't have any electrical draws (i.e. radio, ACC system, etc.) going, you can drive upwards of 50 miles on the battery if you lose an alternator belt, but that would only be for an extreme emergency (it happened to me once on the way to an MB gathering in Centerville, TX; I had to drive 20+ miles on the battery and it was no problem).

    Cheers,
    Gerry

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    Trae (04-11-2018)

  11. #8
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    Re: HOW-TO: Replacing M117 V-belts

    It is possible to change the belts without removing the fan , did it last spring.

  12. #9
    E500E Guru nocfn's Avatar
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    Re: HOW-TO: Replacing M117 V-belts

    Quote Originally Posted by Richter Rox View Post
    It is possible to change the belts without removing the fan , did it last spring.
    Yes it is.
    1994 E500
    249/275 - 8F19 or 8F32 or 8320

    1991 560 SEC
    199/268
    2014 E350 Cab 799/264

  13. #10
    E500E Guru Trae's Avatar
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    Re: HOW-TO: Replacing M117 V-belts

    Well, I did the job a second time on the other 560SEC, and it only took 2:12. Still not a speed demon, BUT at least twice as fast as the first time. Again, THANK YOU GERRY. I would NOT attempt a job if I can't find it in the "how to" section of this site. . . I am still "chicken" to try things on my own without the backup of Jono, Klink, GSXR, Gerry, nocfn, and others that continue to contribute to this site.
    Trae
    1992 500E Renntech
    1993 500E
    1990 560SEC/ 2001 SL500
    1991 560SEC ECE/1995 E320 Cabriolet

  14. #11
    E500E Guru nocfn's Avatar
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    Re: HOW-TO: Replacing M117 V-belts

    Quote Originally Posted by Trae View Post
    Well, I did the job a second time on the other 560SEC, and it only took 2:12. Still not a speed demon, BUT at least twice as fast as the first time. Again, THANK YOU GERRY. I would NOT attempt a job if I can't find it in the "how to" section of this site. . . I am still "chicken" to try things on my own without the backup of Jono, Klink, GSXR, Gerry, nocfn, and others that continue to contribute to this site.
    You leave the fan on this time?
    1994 E500
    249/275 - 8F19 or 8F32 or 8320

    1991 560 SEC
    199/268
    2014 E350 Cab 799/264

  15. #12
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    Re: HOW-TO: Replacing M117 V-belts

    Indeed, this job CAN be done with the fan on. However, since it's only four bolts, it's quick and simple to remove it, and it's MUCH easier and things are more accessible with the fan off the hub.

  16. #13
    E500E Guru Trae's Avatar
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    Re: HOW-TO: Replacing M117 V-belts

    No, took the fan off for easier access.
    Trae
    1992 500E Renntech
    1993 500E
    1990 560SEC/ 2001 SL500
    1991 560SEC ECE/1995 E320 Cabriolet

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