Notes on R&R of Outer LCA Bushings (W124 and others) - PeachParts Mercedes-Benz Forum

Jeremy5848 · #1 05-08-2013, 01:10 AM

A good DIY on the outer LCA (Lower Control Arm) Bushing replacement was written by Sixto in 2008. His thread is at this link. Many others have contributed to the thread. Because the subject has been well covered by others, I present here only some tips, suggestions, warnings and photographs to help you when it is your turn. As usual for me this is a rather long post; if it wears you out just look at the pictures.

The problem: If your car squeaks or groans as you go over speed bumps or otherwise makes complaining noises that seem to come from the rear as you maneuver at low to medium speeds, you may have one or two bad outer LCA (Lower Control Arm, aka Spring Arm or Trailing Arm) bushings.

[digression]

The W124 and some other MB models have a five-link rear suspension. You don't need to know about this to replace the LCA bushing but here it is anyway. First, a picture looking down at the suspension with everything labeled. The various links all have different names depending on which list, book, or diagram you're reading. The "spring link" or "Lower Control Arm" (LCA) is out of sight underneath.

Next is a diagram shamelessly stolen from EPC with my notes in red, giving the names used in EPC. Note that parts sellers may use different names -- be cautious.

How do you tell them apart? Well, the Thrust Arm (Pushing Link) has a plastic cover; the Camber Link (Camber Strut) has a definite curve; the Tie Link (Tie Rod) is smaller than the Pulling Link (Strut). That's about all I can give you. When they're dirty it's even worse, sorry. The four upper links have a bushing at each end; when these fail it's easiest to replace the entire link. The links aren't expensive and it's a simple bolt-in operation.

[/digression]

The LCA's inner bushing likewise can be replaced by buying a new LCA but the outer bushing is pressed into the wheel hub, which you don't want to replace -- you don't even want to know how much a new one would cost! So, you learn to replace the bushing itself.

The following diagram, also shamelessly stolen from EPC with my notes in red, shows the wheel hub and the knuckle where the bushing goes.

The bushing in question, MB 220-352-02-27 (and older, superseded numbers) is common to many MBs. They're not expensive -- Pelican Parts has several different brands at prices in the $25 to $50 (each) range. My personal preference is Lemförder. Replacement of both is advised even if only one is damaged.

Although the wheel hub could be removed from the car and the bushing pressed out (and replaced) using a hydraulic shop press, it's a lot of dis-assembly work and much easier to replace the bushing in situ with a tool made for the job. This tool is not cheap -- the factory tool is about $400 and the after-market tool about $200. That's a lot for what you may never use again. One option is to rent a tool from someone in the forum's tool rental program.

Another option is to borrow a tool from someone; this is what I did this time. You can also build a tool from pieces of pipe, socket wrenches, and other things you may have sitting around. This I did a couple of years ago for my '87 300D. The description of this tool is here. The professional tools are easier to use because they're sized for proper centering of the pieces. With the home-made tool you have to go slower and be more careful. The results are the same.

One of the fears of this job is, "Do I need to mess with spring compressors and other things that will put my life at risk?" The answer is "no." The rear shock absorber acts as a limit stop for the LCA; the spring is held between the rear axle carrier ("subframe") and the spring link (LCA). It cannot escape so long as the inner LCA bolt is left in place. The brake hardware can also be left in place.

With the car securely supported on jack stands (I do one side at a time; you may prefer to jack up the entire rear end at once -- be sure to chock the front wheels) remove the wheel and stick it under the car as an additional safety block just in case. Remove the plastic shield that protects the LCA (two 10 mm screws, 4 clips cast into the plastic) and set it aside. You'll have to bend the brake shield to get at the bolt. Bend it just enough to get your socket wrench in place. Now put penetrating oil on the bolt and nut that attaches the LCA to the hub. The wrench size should be 19 mm and you'll need a fair amount of leverage to break the nut loose. With the nut removed, the bolt will slip out if you're lucky or have to be driven out with a pin punch if you're not. (I had one of each.)

Once the hub is free of the LCA, it will pop up, pulled by the four upper control arms -- their rubber bushings have a twist in them if they were correctly installed. My right side popped up, my left side did not. Apparently someone forgot to pre-load the suspension -- more on that later. With the hub popped up you will be able to see the old bushing in the knuckle. None of this stuff needs to be supported -- it just hangs there waiting for you.

The next two pictures show how the tool works. I used the Baum (aftermarket) tool borrowed from a friend but the others including the home-made ones should work the same way. Note that the work is done from the rear: the tool pulls the old bushing out to the rear and pushes the new bushing in from the rear. To make room for the tool you'll need to bend the brake shield out of the way. I used large pipe pliers for this task. Remember to bend the shield back when you're finished!

Once the tool is in place, the extraction process is as simple as turning a wrench. I didn't have the correct Metric socket for the Baum tool so I used 1-1/16 inch. Make sure the bare knuckle is clean and rust-free. If necessary, use fine sandpaper or steel wool to clean it but be gentle -- you don't want to enlarge the hole! Put a little oil or grease on the inner surfaces to protect them for the installation of the new bushing. Lubricate the outside of the bushing too. Another advantage of the professional tool is that you don't have to check to make sure the bushing is correctly in place. The tool automatically stops when it can't go any farther. With the home-made tool you'll have to watch carefully or you'll go too far and the bushing will start out the other side.

With the new bushing in place you're ready to button up. Pull the hub down (or jack the LCA up) until the holes are aligned and insert the bolt, then screw on the nut and torque to 120 NM (about 90 ft-lbs). Bend the brake shield back into place, making sure it won't drag on either the brake rotor or the wheel. Re-install the plastic shield on the LCA and the wheel on the hub and you're done with one side. "Repeat as needed."

[edit] Mercedes specifies that the axles (half-shafts) must be parallel to the ground when the rear suspension bushings are tightened. This normally means having the car on the wheels and sitting normally with a normal load. With a wheel off the car, you can simulate this by jacking up the hub until the axle is parallel to the ground. There will be a tendency for the body to lift off of the jack stand so "situational awareness" is critical. For the Outer LCA bushing (which really isn't a bushing) this is thought to be unnecessary but I mention it for those who want to be doubly sure their installation is correct. [/edit]

Returning to my comment on the right-side hub, the one that wouldn't pop up, remember? To fix it (before I reconnected the LCA) I used a bottle jack and raised the hub as high as it would go, then loosened all of the bolts on the four upper links (a nut and bolt on each end). I didn't remove them, just loosened them. Two of the bolts are eccentric and are used for adjusting the alignment of the rear suspension. Try not to move the bolts when loosening the nuts (I did, unfortunately). Once I had the connections all loose I made sure the hub was still as high as it would go and then tightened all of the nuts. With tension properly on the rubber bushings the hub now sat where it was supposed to, a couple inches above the LCA, until I pulled it down and bolted the hub back into the LCA and its new bushing.

As a final step, I'll take the car to "Ralph" here in Santa Rosa, California and get the alignment checked and adjusted if necessary. Even if you don't mess up the links like I did you should get the alignment checked because of the new bushings.

[edit] Ralph tweaked the camber a little on the left side, a result of my inept boogering of the bolts holding the links on that side. All is well now. [/edit]

Jeremy

engatwork · #2 05-08-2013, 06:08 AM

Good pictures - thanks.

pwogaman · #3 05-08-2013, 07:36 AM

Fantastic pictures!

Walkenvol · #4 05-08-2013, 08:25 AM

How did you determine your problem was the hub bushing alone and not the bushing on the subframe end of the LCA or one of the several other link bushings?

gsxr · #5 05-08-2013, 10:38 AM

Excellent documentaton, Jeremy. A few other keywords to add to this topic, for SEO: The bushing is also known as the "support joint" which is located at the bottom of the "rear wheel carrier".

I've done this job on almost all of my cars. If the joint is original, it is almost always toast after 20+ years and/or over 150kmi. You can inspect it via flashlight and if any of the dust boots/seals are damaged, it should be replaced, as that means failure is in the not-distant future (even if it's not yet making noise). Omegabenz says that when these joints wear, it will cause excessive negative camber in the rear, I believe he said new bushings caused a significant change in camber. That helps your tires last longer and offsets the cost of the bushings/joints and special tool.

Warning: There are some cheap, off-brand bushings / joints on the market from Uro / APA / FEQ / Pex. If the price is under $10, it's garbage, don't waste your money. Under $20 is highly suspect (I've seen Febi and Meyle around $20 and I'd be nervous about those). OEM is Lemforder, these are usually $25-$35 depending on vendor, Coretco should be ok too. Genuine MB is approx $50 list, $40 wholesale. The part numbers have superceded nearly a dozen times but they are all interchangeable. Try 220-352-02-27 when searching. Pelican offers Lemforder at a great price.

Note about the tool. The aftermarket SirTools version is approx $120 shipped from several vendors, links below. The Baum tool is $160 from "alkyracer101" on feeBay. Links below:

http://www.toolsource.com/metal-clad-bushing-p-112946.html

http://www.tooldiscounter.com/ItemDisplay.cfm?lookup=SIRM0085

http://zdmak.com/wbstore/main.asp?action=PROD&PROD=M0085&CTMP=1

http://www.ebay.com/itm/121080269082 (currently sold out, but

click here) to check in the future)

Photos from my R&R's are at this link:
http://www.w124performance.com/images/W124_subframe/wheel_carrier_joint/

Photos of the factory tool are here, scroll to the bottom:
http://www.w124performance.com/images/W124_subframe/subframe_tools/

Jeremy5848 · #6 05-08-2013, 11:07 AM

Quote:

Originally Posted by Walkenvol

How did you determine your problem was the hub bushing alone and not the bushing on the subframe end of the LCA or one of the several other link bushings?

"Determine" is too big a word for me . . . I "figured out" it was the hub bushing by replacing it and the squeak went away! It was pretty much an educated guess. I had advice from GSXR and others, and I was able to closely inspect the other bushings -- they looked good (the hub bushing is hard to see). Finally, I think a failed bushing in another link including the inner LCA bushing would make a different noise -- the hub bushing's noise was definitely metallic. As a final note, the hub bushing really isn't a "bushing," it's more of a "flex joint."

Jeremy

fdanielson · #7 05-09-2013, 07:04 AM

Quote:

Originally Posted by Walkenvol

How did you determine your problem was the hub bushing alone and not the bushing on the subframe end of the LCA or one of the several other link bushings?

If you own a W124 it's pretty simple. They've either been replaced or you need to replace them. You can take off the rear wheel and look down from above the bushing with a flashlight to see the torn dust boots.

Zulfiqar · #8 05-09-2013, 08:54 AM

that is why in most EU countries - this is usually called squeak joint. When you hear a squeak - replace this item.

Jeremy5848 · #9 05-09-2013, 11:51 AM

"Squeak Joint" is as good a name as I've heard, even though it sounds like a tavern where reptilian Zindi toss down live mice with their drinks.

In any case, this thing actually isn't a "bushing" at all, it's more of a "spherical bearing." I put together a couple of pictures (thank you, Photoshop) showing what the insides look like. The first picture shows a new part, then the bad one removed from my '95 E300, then that same one cleaned up so only the metal parts remain.

The inner section (which in use is bolted to the LCA) is spherical and can rotate or swivel inside the outer part, which is pressed into the knuckle on the wheel carrier. The range of tilt available to the bearing is about +/- 15 degrees, as the second picture shows.

The bearing is packed with heavy grease; the rubber parts on the ends are grease seals. When the rubber gets old, it splits, allowing some of the grease to escape and water to get in. This rusts the steel surfaces, which rub together, giving you a "squeak joint."

Jeremy

whunter · #10 05-09-2013, 03:37 PM

Here are two DIY's for more data.

Pelican Mercedes-Benz Tech Article - Replacing Your Rear Lower Control Arm Bushings - Mercedes Benz - 190E, W124, W126, W201, W123

Pelican Mercedes-Benz Tech Article - Replacing Your Rear Multi-Link Suspension - Mercedes Benz - 190E, W124, W126, W201, W123

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Zulfiqar · #11 05-09-2013, 03:47 PM

Quote:

Originally Posted by Jeremy5848

"Squeak Joint" is as good a name as I've heard, even though it sounds like a tavern where reptilian Zindi toss down live mice with their drinks.

In any case, this thing actually isn't a "bushing" at all, it's more of a "spherical bearing." I put together a couple of pictures (thank you, Photoshop) showing what the insides look like. The first picture shows a new part, then the bad one removed from my '95 E300, then that same one cleaned up so only the metal parts remain.

The inner section (which in use is bolted to the LCA) is spherical and can rotate or swivel inside the outer part, which is pressed into the knuckle on the wheel carrier. The range of tilt available to the bearing is about +/- 15 degrees, as the second picture shows.

The bearing is packed with heavy grease; the rubber parts on the ends are grease seals. When the rubber gets old, it splits, allowing some of the grease to escape and water to get in. This rusts the steel surfaces, which rub together, giving you a "squeak joint."

Jeremy

Its looks like a ball joint - I believe a similar part exists on BMWs too which are the major cause of camber problems. On them they are actually called ball joints.

tisdale36 · #12 08-16-2016, 02:25 PM

On the EPC picture of the thrust arm, how do I get the pin marked 123? My bushing is "melted" to it?

gsxr · #13 08-16-2016, 02:30 PM

Quote:

Originally Posted by tisdale36

On the EPC picture of the thrust arm, how do I get the pin marked 123? My bushing is "melted" to it?

Item #123 in that diagram is a thin metal sleeve, designed to take up the space when a smaller M10 bolt is used inside an M12 hole.

See photo below, the sleeve is on the left / center of the picture.

tisdale36 · #14 08-16-2016, 09:17 PM

How do I install the ones your showng? I have those from the Meyle kit but they didn't make sense but I may not have given it enough time to process. Of course I was looking at it as though those sleeves had to go back.

tisdale36 · #15 08-16-2016, 09:22 PM

Also did you convert your headlights?