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Thread: HOW-TO: Changing Motor Mounts on Late W124 (M104 inline-6 engine)

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    HOW-TO: Changing Motor Mounts on Late W124 (M104 inline-6 engine)

    Over the past 6+ months (that I can remember), I've noticed my wife's E320 wagon (1995 S124) has had a noticeable shake/shudder upon starting up the engine, and upon shutting it down. Also a bit of a tremor at idle -- normally the M104 has a glass smooth idle (and it still has, in terms of the engine itself) but I just noticed in recent weeks a bit of a tremor through the dashboard and steering wheel when the car was idling. Nothing to be alarmed of, but I didn't like the "feel" of the engine shudder at startup and shutdown, in particular.

    We purchased the car 7 years ago and I'd never had the motor mounts done, or replaced them myself. Going through my records, I found that the motor mounts had been replaced at 132,000 miles, back in 2006 a couple of months before I purchased the car. The car currently has 195K miles on it. So, the mounts lasted 63,000 miles. I installed a new transmission mount in late 2009, so this mount did not need replacing at this time. Normally though, it's an excellent idea to replace both motor mounts and transmission mount at the same time, in order to preserve correct alignment of the drivetrain.

    I ordered new factory MB motor mounts last week from parts.com, with intent to change them over the Thanksgiving break. And, today (Saturday) was the day. I started the job around 10:15 AM and finished around 1:30 PM, and spent around 30 minutes cleaning up the garage shop, cleaning and putting away my tools, and testing out the car.

    Here's the procedure I used to replace the motor mounts. If your car has 80,000 or more miles on a set of motor mounts, and you know they haven't been changed, it's a good idea to change them out. At 100K miles, the motor mounts are past due for changing. It is good not to go with cheap aftermarket mounts - these are hydraulic mounts and thus it's a good idea to go with a quality factory part or OEM part such as Lemforder. The motor mounts that I changed out were Boge units and as I said, they went 63,000 miles. I believe that a good set of mounts should go 75K+ miles, so I'm a bit surprised these Boge units didn't go the full distance. If I HAD to go aftermarket, I would go with a Lemforder/Sachs/Boge mount, but my personal policy with all MB rubber items is to go factory ONLY. I am told that Sachs/Boge/Lemforder (all the same company) and Corteco are OEMs for MB for motor mounts; however the replacement mounts I received from MB had no manufacturer's brand or logo on them. STAY AWAY from Meyle mounts (and all Meyle parts, IMHO) as they are made in China.

    If you haven't done this job before, I would allot approximately 3-4 hours for it. You will need the following tools:

    • pair of ramps, or set of at least two jackstands for working underneath the car (and you will be spending A LOT of time on your back under the car)
    • a hydraulic floor jack, preferably with a 8-12" length of 4x4 or 4x6 to put underneath the oil pan to lift the engine
    • 1/4", 3/8" and 1/2" ratchets, and sockets. You will also need short and medium-length extensions.
    • 17mm "stubby" combination wrench
    • Flashlight and a halogen or other type of worklight (two preferred -- one shining down in engine bay, the other on the ground under car)
    • Hammer or ball peen hammer
    • 8mm, 13mm and 17mm sockets
    • Can of WD-40, Liquid Wrench or PB Blaster, or other penetrating oil
    • Magnetic tray (to hold removed bolts and clips)


    Here's the procedure to use for changing the M104 / W124 motor mounts:

    Drive the car up on ramps and secure the rear wheels with chocks, 4x4 or other roll-back preventer

    Open the hood. Remove fan shroud by releasing center coolant hose clip, swiveling round plastic piece, removing two metal clips from main shroud, and carefully lifting pieces up and out from behind the radiator. You can carefully place the two plastic fan shroud pieces on the center of the engine, leaning against the windshield (you want the pieces to be out of the way of either side of the motor).

    Fan shroud removed and set aside. View looking down behind the radiator with the fan shroud removed.
    IMG_1693.JPGIMG_1694.JPG

    Using your flashlight or work-light, looking down in the engine bay, take a good look at the locations of the top bolts for the motor mounts and the locations of the flanges that attach the mounts to the sides of the block. Do this on both sides of the motor. Note that the intake manifold and assorted linkage pieces severely restrict access to the motor mount on the driver's side of the car; the passenger side is quite a bit more exposed despite the presence of the exhaust manifold.

    Get underneath the car. Remove the plastic belly (encapsulating) pan and set aside (attached to the underside of the car with six 8mm bolts). You will want to clean this with some disposable rags and brake cleaner as the very last step of this job, before re-attaching it to the car.

    While underneath the car, scope out where the bottom bolts for the motor mounts are. These are 17mm bolts and you will want to notice the type of ratchet and extension length that you'll need to loosen them. You should use a 1/2" ratchet with a medium-length extension. A breaker bar on the ratchet handle (perhaps created from an 18" length of steel pipe) will help you break them free, as they are torqued down to 70 Nm.

    While underneath the car, use your flashlight or worklight and look around for other things that seem out of order. Things like muffler and exhaust hangers; ball joint rubber boots that are ripped, and other worn rubber items. Also look for any oil leaks, and perhaps the source of them if possible. Or take some brake cleaner and clean up any loose oil, for diagnosis in the near future. In my case, I found a broken exhaust hanger at the catalytic converter about mid-way back on the car. I was able to supply an exact MB replacement hanger for this broken one, noting that this hanger had last been replaced not quite 3 years ago.

    Views of the broken exhaust hanger compared with new hanger; and new hanger mounted on car.
    IMG_1682.JPGIMG_1683.JPGIMG_1684.jpg

    Loosen the bottom bolts on the motor mounts, after scoping them out. Remove and set aside the two bottom motor mount bolts.

    Location of the bottom motor mount bolt. Removing bottom motor mount bolt with 1/2" ratchet.
    IMG_1686.jpgIMG_1687.jpgIMG_1688.jpg

    Passenger side motor mount bottom bolt location.
    IMG_1689.jpgIMG_1691.jpg

    This is what the motor mount looks like (resting on car's frame), immediately before engine is lifted.
    IMG_1690.jpgIMG_1692.JPG

    Next, you're going to lift the engine, using the block(s) of wood and your hydraulic jack. I used two short (12") lengths of 2x4, stacked on top of each other, but it's preferable to use a single piece of 4x4 or 4x6. Position the wood on the jack pad and roll it under the cast aluminum oilpan. CAREFULLY and SLOWLY jack up the pad, until the wood meets the bottom of the oil pan. Keep jacking SLOWLY and you will see the front end of the car rise a bit, and then you will see the engine continue to rise. You want to only raise the motor about 1", so that the bottoms of the motor mounts are off the frame of the car. You will be able to see from above when the mounts have lifted off the frame of the car. You will hear a bit of creaking and groaning; just take it slowly and don't raise the engine up too far -- just far enough to get the bottoms of the mounts about an inch off the frame of the vehicle.

    After you've got the engine lifted and the jack secure, you can proceed in one of two ways: you can remove the mounts themselves from the motor mount flanges using the single 17mm top bolt that fastens the mounts to them, or you can remove the entire flanges from the side of the block. Given the tight clearance (tighter on the driver's side) I decided to remove the whole flange+mount assembly from the block on both sides, and then remove the mounts from them on the shop floor, reinstalling the new mount at that time.

    The flanges are held to the block by four 13mm bolts in a rectangular pattern - it's very straightforward. On the passenger side, all four of the 13mm bolts are quite easy to get to; on the driver's side three of the four are easy to get to, and the fourth isn't all that hard, just a bit more difficult. All 8 of the flange bolts can be accessed from below the car. I used a 13mm socket (a couple of the bolts required extensions; others just the ratchet+socket) and my 3/8" ratchet and didn't have any problem loosening them by hand -- no breaker bar needed.

    The other way to go would be to use a 17mm "stubby" combination wrench to remove the 17mm top bolt that holds the motor mount to the flange. You can use the ball peen hammer to carefully hit the end of the wrench to loosen the motor mount top bolt -- you have a bit more room to do this on the passenger side. Many people have reported success with this approach (particularly easy on the passenger side) but in scoping this out and with some cursory work with a stubby 17mm combo wrench, I quickly opted to go for the "flange removal" approach instead. You can go either way. There is not enough room above the flanges on either side to get a 17mm socket & ratchet on there to remove the bolt, so you have to go with a box-end combo wrench for security if you choose to go this way.

    View of the car's frame where the motor mount sits, as seen from above. This is with the motor mount and flange removed from the car. The hole is where the bottom bolt goes up from below into the bottom of the motor mount.
    IMG_1696.JPG

    Driver's side motor mount and flange assembly as removed from the car.
    IMG_1697.JPG

    Removing the old motor mount from the flange.
    IMG_1698.JPG

    In any case, you can see my replacement process for dismounting the motor mount from the flange on the garage floor, and installing the new mount. Note the difference in height between the old and new motor mounts -- it was about a 1/2" on the driver's side and more than 1/2" on the passenger side!

    Old and new motor mounts, compared.
    IMG_1701.JPGIMG_1702.JPGIMG_1705.JPG

    New motor mount attached to flange. Note that there is a raised "shark fin" on the top of the motor mount that must be fitted appropriately into the notch in the flange.
    IMG_1704.JPG

    "Boge" moniker and part number on old motor mount.
    IMG_1706.JPGIMG_1707.JPG

    After installing the mount onto the flange, I put the flange back up into position on the driver's (tougher) side, and started the four bolts that held the flange to the block. Tightened the flange bolts as tight as I could, and noticed that the bottom bolt hole was about 1/2" mis-aligned, so that I couldn't get the bottom bolt up through the frame and into the bottom of the motor mount.

    Presented with this challenge, I decided I'd just wait until I replaced the other motor mount on the passenger side, and then I'd deal with it. So I followed the same procedure with the passenger side -- removing the four bolts that hold the flange to the block, remove the flange/mount from the car, replace the mount, and re-bolt the flange+new mount back to the block and tighten everything up. That bottom bolt too, on the passenger side, was about 1/2" off so that I couldn't get the bottom bolt up through the frame and into the bottom of the new mount.

    So, what to do? Well, first I lowered the jack slowly so that the motor mounts were resting on the frame, but obviously not in the correct position (off by 1/2" as mentioned). Next, I removed the long, tubular handle from my floor jack (after ensuring that the jack was as tight as possible). Then I inserted the handle between the engine and the frame on the driver's side as a giant pry-bar, and gently levered the engine over toward the correct orientation.

    Getting underneath the car to check my levering process, I was astounded to find both holes in the frame and mount on BOTH sides of the car, EXACTLY lined up !! After thanking my lucky stars and the God who created them, I hastily inserted and started the bolts on both sides, and tightened them up with the appropriate 70 Nm of torque. Then I double-checked the eight 13mm flange bolts to ensure that were nice and tight in the block.

    That was it. I replaced the bottom encapsulation panel (after cleaning it with rags and brake cleaner) and also replaced the fan shroud carefully.

    Then, it was time for the big test. Started up the car and WOW, was it quiet. No shudder on startup. Save for the noise of the engine running through the open driver's window, I couldn't tell it was running as there was no vibration through the dashboard or steering wheel. I shut off the engine and again, NO shudder! Took the car for a test drive of several miles and all seemed well, so was happy to say that another job was done.

    Cheers,
    Gerry

  2. #2
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    Re: HOW-TO: Changing Motor Mounts on Late W124 (M104 inline-6 engine)

    Hello, I am a new member of this forum. I found this DIY instruction on the engine mounts swap, and wanted to say big THANK YOU, this instruction was extremely helpful, without which I probably wouldn't of started this by myself. It was somewhat challenging, especially the driver side. I have spent about 4 1/2 hours for the entire job, but I am glad i did it!
    Thank you very much, once again!

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    Re: HOW-TO: Changing Motor Mounts on Late W124 (M104 inline-6 engine)

    I'm glad you found the information helpful. That's why we try to post quality how-to information on this site. This happened to be because I own a 6-cylinder W124, as do quite a few of our members, so I thought it would be of interest to a number of people.

    Thanks for the note.

    Regards,
    Gerry

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    Re: HOW-TO: Changing Motor Mounts on Late W124 (M104 inline-6 engine)

    Fyi,

    The 560sl exhausthangers have the wire reinforcement.

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    Re: HOW-TO: Changing Motor Mounts on Late W124 (M104 inline-6 engine)

    I realize this is an old thread, but would like to ask a question.
    I have a 1991 MB 300-SEL W126 - so the process might be a little different.
    For those of you who've done a motor mount replacement on any 80s thru early 90s MB, did you do one mount at a time, leaving the other side attached to chassis(if even possible to do so) or did to pull both mounts at the same time?
    Thanks.

  6. #6
    E500E Guru JC220's Avatar
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    Re: HOW-TO: Changing Motor Mounts on Late W124 (M104 inline-6 engine)

    I renewed the motor mounts recently on my 320CE. Rather than remove the brackets from the engine I bought 1x extra socket and cut it down so it would fit on top of the bolt under the exhaust. Then it was easily loosened from above with the Air filter box removed. On the other mount going in below with an S Shaped spanner worked best to access the top bolt on the other side.

    I did one mount at a time using a block of wood positioned on that side of the pan to gently lift the engine up and get enough room to slide the new mount into place. FYI all- Lemforder w124 engine mounts are now made in China

    IMG_5529.JPG IMG_5531.JPG IMG_5530.JPG IMG_5517.JPG
    1987 w124 200 E36 AMG Project car - ongoing 1990 w124 300E-24 Fully Restored
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  8. #7

    Re: HOW-TO: Changing Motor Mounts on Late W124 (M104 inline-6 engine)

    I am curious if anyone has ordered OE mounts.
    On my E320, the mounts were replaced less than two years ago with Lemforder and one of them failed last week (less than 10km). The parts were covered under warranty but out another $200 for labor. WTF! I wonder if is the same factory in China that is making URO and Lemforder....

    Quote Originally Posted by JC220 View Post
    I renewed the motor mounts recently on my 320CE. Rather than remove the brackets from the engine I bought 1x extra socket and cut it down so it would fit on top of the bolt under the exhaust. Then it was easily loosened from above with the Air filter box removed. On the other mount going in below with an S Shaped spanner worked best to access the top bolt on the other side.

    I did one mount at a time using a block of wood positioned on that side of the pan to gently lift the engine up and get enough room to slide the new mount into place. FYI all- Lemforder w124 engine mounts are now made in China

    IMG_5529.JPG IMG_5531.JPG IMG_5530.JPG IMG_5517.JPG

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    Re: HOW-TO: Changing Motor Mounts on Late W124 (M104 inline-6 engine)

    Quote Originally Posted by JC220 View Post
    FYI all- Lemforder w124 engine mounts are now made in China
    Quote Originally Posted by mikeym View Post
    I am curious if anyone has ordered OE mounts.
    On my E320, the mounts were replaced less than two years ago with Lemforder and one of them failed last week (less than 10km). The parts were covered under warranty but out another $200 for labor. WTF! I wonder if is the same factory in China that is making URO and Lemforder....
    I would be exceedingly leery of anything Lemforder that is made in China - particularly rubber parts. I would have sent them back and just gotten the MB factory mounts. Not cheap, but would have been good for another 10 years.

    From what I see, the factory parts (124 240 19 17) for the E320 (M104) can be purchased from online MB parts dealers for around $130 apiece. It also appears that the Lemforder and Corteco motor mounts for the 3.2-liter M104 engines are made in China.

    So, it is advisable just to get the MB mounts for this application.

    Cheers,
    Gerry

  10. #9

    Re: HOW-TO: Changing Motor Mounts on Late W124 (M104 inline-6 engine)

    mikeym: I replaced the motor mounts ( using Gerry's How-To write up ) a couple of years ago on my M104 equipped E320 using factory parts. I believe Corteco is the OE supplier. I typically purchase from OEdiscountparts.com. Free ground shipping on orders over $50. Genuine factory parts. This site is operated by an MB dealer in Asheville, NC.

    Regards,

    Peter Weissman

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    Re: HOW-TO: Changing Motor Mounts on Late W124 (M104 inline-6 engine)

    As with Lemforder, I believe Corteco is now also making their M104 mounts in China, which is unfortunate. This may have been something that happened in the past year or two.

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    Senior Member LWB250's Avatar
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    Re: HOW-TO: Changing Motor Mounts on Late W124 (M104 inline-6 engine)

    On all of the MB engine mounts I have changed out, I do one side at a time. Why? It allows you to maintain the alignment of the mount and related bolt holes. I'll loosen all of the fasteners on one mount, take the top bolt out first, raise the engine, then remove the bottom fasteners and slide to old mount out. Installation is the reverse of removal.

    It's been my experience that by just lifting up one side of the engine at a time the remaining mount keeps the mounts properly aligned so that when you install the new mount all of the bolt holes line up properly. If you remove both mounts at the same time and raise the engine, you risk moving it out of alignment with the holes for the mount fasteners, making it a bit of a struggle to get the engine moved around to line things back up.

    Just my $0.02.

    Dan

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    Re: HOW-TO: Changing Motor Mounts on Late W124 (M104 inline-6 engine)

    Peter - Any idea on where the OE part is made?

    Last year, I bought visco fan online and also ordered the one from dealership. Both were identical, made by Behr and in China. I am not fully convinced that OE parts is always the safe bet. (I doubt that Corteco or Lemforder are making special parts for MB outside of China)

    Quote Originally Posted by geraniumtr View Post
    mikeym: I replaced the motor mounts ( using Gerry's How-To write up ) a couple of years ago on my M104 equipped E320 using factory parts. I believe Corteco is the OE supplier. I typically purchase from OEdiscountparts.com. Free ground shipping on orders over $50. Genuine factory parts. This site is operated by an MB dealer in Asheville, NC.

    Regards,

    Peter Weissman

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    Re: HOW-TO: Changing Motor Mounts on Late W124 (M104 inline-6 engine)

    Quote Originally Posted by geraniumtr View Post
    I believe Corteco is the OE supplier.
    I believe that for all 124 chassis engine mounts, Boge was the OEM, and Corteco was not OEM for any mounts on the 124. AFAIK, the supply of quality engine mounts for any 124 chassis is pretty much gone from the aftermarket, and we're stuck with buying OE dealer at insane prices, even from the discount dealers. Corteco is generally a reboxer and while they may have reboxed OEM items, I don't believe they supply those items to Mercedes.

    Corteco is now a brand of Freudenberg, merged under CFW a few years ago, and CFW is now their parent company. CFW is an abbreviation for "Carl Freudenberg Weinheim". For the 210 chassis, CFW is indeed the OEM and the OE/dealer 210 mounts have the CFW logo. Also, CFW is OEM for a number of W211 suspension components (ball joints, suspension arms/bushings). However, CFW being OEM for the 210/211 parts does not mean they are OEM for any or all 124 items they may sell. The Corteco M119 engine mounts were Chinese junk. Be careful out there...


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    Re: HOW-TO: Changing Motor Mounts on Late W124 (M104 inline-6 engine)

    After changing out both mounts I agree with Gerry. I bought an offset wrench specifically for the top bolt and my plan was to not remove bracket. After struggling for hours yesterday without the top bolt moving at all I conceded defeat and removed the bracket. I had started on the passenger side and the bracket is easily removed. I thought I could then get the top bolt off with a 1/2 wrench. Nope. So I found a way to brace the bracket broke out my impact gun and 10 seconds later all was good.

    I then tackled the drivers side. As Gerry noted three of the bolts are easy the fourth which is upper rear is a PITA. Helps to have a fine tooth ratchet. Eventually I got it. Used the impact gun again and I was good to go.

    I removed only the bottom bolt from the side I was working on. The passenger mount needed a little help to line up on the bottom. Drivers side lined up perfectly.

    The best part is starting the car and not feeling any vibration through the steering wheel.

    A pic of the old and new mounts. Definitely had compressed but not leaking.

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