HOW-TO: Replace Idler Arm Bushing

[RicardoD]

ADMIN EDIT: To check if the idler arm bushings need replacement, click here.


Part of any front end suspension refurbishment should include replacing the Idler Arm Bushing which is part of the overall steering linkage. It is supposed to cure all sorts of front end feel issues on your car and yours is probably 24 years old like mine. So per the 500eboard guidance I tackled this job.

Idler Arm Bushing Kit: Mercedes part # 129-460-00-19 (nut, bolt, 2 washers, 2 bushings) - MSRP July 2021 is $184, discount price $136 from Naperville. UPDATE - this kit is now NLA (link), order bushings separately, details below.

GSXR edit: The bushings are available separately, and are were cheaper than buying the complete kit [before it went NLA]. A new self-locking nut is recommended but the old nut can be re-used with threadlock. Prices below are as of July 2021 December 2024: ​

​

NLA Kit 129-460-00-19 consists of:​

• 129-463-00-50 = Bushings, 2 required, $51 $55 MSRP each
• 000960-016299 = Bolt, M16 x 150mm (Possibly NLA. Need superceded part number)
• 910113-016002 = Self-locking nut, M16, $8.50 $10 MSRP
• 129-463-00-56 = Upper heat shield (cup-shaped washer) - $5.50 MSRP, NLA
• 129-463-00-77 = Lower flat washer - $4.20 MSRP

Note: Thick washer (p/n 000125-017016, $3.50 MSRP) between the idler arm and upper heat shield is not included in the above kit. ​

Special tools needed:

• 24mm deep socket, 6 sided hex [GSXR edit: A standard-depth socket will also work, see post #54.]
• 24mm combination wrench (larger than typical found in most home garages)
• Torque Wrench capable of 150Nm
• WIS Document #: 46-6317 (PDF attached below)

Jack up the front of your car properly or put it on your handy lift (I have a MaxJax mid-rise two post lift in my garage, best tool in it).

Drop the lower engine tray, 8mm socket required

Location of Idler Arm Bushing: passenger side of car, accessible from underneath, after removing lower engine cover (engine out photos below courtesy of GXSR).


You should also consult Lowman's awesome general overview of the World's Most Expensive Bushing Kit video (330 Euro he said! What? Half that in USA via mboemparts). Lowmania forever!!!
[video=youtube_share;yj07vBv-kK8]

First thing is to remove the Idler Arm Heat Shield. I removed the pair of heat shields by removing the two 10mm bolts. Note the loose strap piece comes off as well.





Now you are faced with removing the monster 24mm nut. I applied some Kroil in the morning and then hit it with my Ingersol Rand Air Impact gun an hour or so later and got no where. Nut wouldn't move. [GSXR edit: If the nut is not seized, an impact wrench SHOULD work to remove the nut. Make sure to connect the socket directly to the impact wench, without any extensions. Also verify the wrench is set to max torque, and that you have maximum pressure available for an air impact. See post #54 for details.]

Then I proceeded to strip the nut with my breaker bar because I did not have a proper impact wrench 6 sided 24mm deep socket. I just had my regular Craftsman multi-point 24mm socket. So let this be a warning to you. Perhaps, Kroil or PB blaster overnight, followed by heat via blow torch, followed by proper 24mm 6 sided deep impact gun socket would have done the trick. Lowman, of course, must have proper tools, and isn't a Shade Tree Mechanic Hack like I am.

So now we brute force it by cutting off the Idler Arm nut via a Dremel (multiple cutting wheels and 1/2 hr - thx nocfn for the tip) or if you have an 4 1/2" Angle Grinder and cutting wheel this will take a few minutes. However, to fit a larger angle grinder with cutting wheel you need to remove the C shaped cross member that is held on by four 6mm Allen Bolts (13mm wrench to hold nut on back side).

(Shade Tree Mechanic Pro Tip: Go to Harbor Freight and buy the cheapest angle grinder they sell. Its like $15 and then buy the grinder disc multi-pak which includes some cut-off wheels for around $5. This will leave you $20 poorer and it works just fine for occasional homeowner use. I've used mine like 5 times in 6 years. You will be amazed the jams this China special grinder will get you out of)



Now sparks will fly, wear goggles, mask, etc and let the tool do cutting work. Be careful you don't want to be grinding anywhere else like the transmission fluid line nearby but with the back side guard on the wheel I had no issues. And then Viola! Nut is gone!




Now you can tap out the bolt a bit , and use a large pair of pliers to remove the lower bushing.





EPC screenshot showing the individual part numbers for the bushing kit:

 

[RicardoD]

Part 2:

With a long screwdriver and hammer you can start to tap out the upper bushing which is required to remove the bolt. You can then slide out the bolt and bushing (just like Lowman shows you in his video). Lowmania forever!!



Now you need to put the bushings, bolt, washer back in to the tube. Lowman's tip was that you don't need to remove the tie rod and drag link per WIS. This is where you will start to understand why the workshop manual tells you to do so. You may in fact start cursing our Norweigan brother Lowman at this point as well (I was guilty of this). However, remember that putting this new bushings back in is the exact reverse of removal and watch how Lowman does it in his video. Do NOT put the bottom bushing in first. Look at the photo below, here I am mid step. I did lube up my bushing with Dow (molykote) 111 a o-ring lubricant I use. You need to use a rubber safe lubricant not some petroleum based product that will destroy the bushing.

Note you must use the correct order on the bolt, idler arm, washer, bushing cap, bushing..



Just with hand force I was able to get most of the bushing in. You can get just enough of the bolt to stick through through the bottom of the tube, then you can temporarily use the large bottom washer and nut to help screw drive the rest of the top assembly into the idler arm tube.



Then when enough of the bolt sticks through the bottom you can install the bottom bushing, washer and nut and start screwing everything together. I eventually had to use a 24mm combination wrench on the top bolt head to prevent it from spinning.



Everything compresses down together nicely and you have to finish off the nut with 150 Nm of torque per the workshop manual.



Re-assemble the heat shield and put the cross member back on if you had to remove it to cut off the bolt. And that's it.

 

[emerydc8]

Thanks to both of you, I just ordered two bushing sets from mboemparts.com (one for each car) and I'll be heading to Sears tomorrow to look for a hex-sided 24mm socket. On this side of the pond the bushings are only $134.68 each, presuming they are still available.

Lowman: Glad you didn't go with the URO part!

Ricardo: Did you find a hex 24mm socket at Harbor Freight?

 

[luckymike]

Great write up, Ricardo.

I'm surprised at how difficult it was. I think when you get around to doing this job on your C126, you'll be very pleasantly surprised. It was a piece of cake on both of ours.

 

[RicardoD]

Ricardo: Did you find a hex 24mm socket at Harbor Freight?

I never bought one, too late by the time I damaged the nut. 24mm slightly deep hex sides socket is best. Something like this though not sure it’s deep enough. I’m sure hazet has the perfect one for $100!!

TEKTON 14297 1/2-Inch Drive by 24 mm Shallow Socket, Cr-V, 6-Point https://www.amazon.com/dp/B000NQ1802/ref=cm_sw_r_cp_tai_cz-zBb500C6B4

EDIT: found it
TEKTON 47814 1/2-Inch Drive by 24 mm Deep Impact Socket, Cr-V, 6-Point https://www.amazon.com/dp/B000NPXKDQ/ref=cm_sw_r_cp_tai_mD-zBbC553454

 

[gerryvz]

You can get the 24mm six-point deep socket at any Northern Tool store for $5.00. It has a number of uses beyond just this one, so it's a good one to buy.

https://www.northerntool.com/shop/tools/product_200653935_200653935

Unfortunately for those folks out West, Northern Tool stores are only in the Eastern USA.

Craftsman also has an impact socket that will work: https://www.craftsman.com/products/craftsman-24mm-lsr6pt-dp-1-2-00916086000

Cheers,
Gerry


Indeed....lowmania 4-ever!

 

[TerryA]

Way to Go Ricardo!!

You and Stephan are the new “International Tech Team”

On my car a while back I replaced all tie rod bushings , steering links the dragstrut and the shock absorber but NOT the Idler Arm Bushing.

At the time I was not aware that it should be changed. So far no problem but it’s nice to know that I can do this job if I have to.

Great Info!!

Take Care

 

[nocfn]

While I had the right socket, she was just about welded on and I too had to cut mine off, or as they say in England - Saw It Off!

 

[RicardoD]

I just bought this 1/2 drive deep socket , 6 sided, set from Tekton via Amazon. Goes up to 24mm. Reasonable price.

ADMIN EDIT: Link to Amazon: Amazon.com

Above link is sold out. Similar link: Amazon.com

 

[nocfn]

I just bought this 1/2 drive deep socket , 6 sided, set from Tekton via Amazon. Goes up to 24mm. Reasonable price.

Excellent with breaker bars too.

 

[Glen]

I just bought this 1/2 drive deep socket , 6 sided, set from Tekton via Amazon. Goes up to 24mm. Reasonable price.

Nice. No skips and easy to read sizes!

 

[Lowman]

Thanks to both of you,

Lowman: Glad you didn't go with the URO part!

you are welcome

Well..yeah in many ways im glad that i didnt..but i have to say i would love to buy one..just to see how it "feels like".
As i did say in the video...often stuff about quality is hearsay...and not first hand information and experience..so like in this case..i havent tried the URO part myself.
I did get a cheap idler arm bushing at first for my 190e though..and that i experienced was pretty much a crap part..so indeed cheaper parts "tend" to be "you get what you pay for "material.

What is funny is that on the 129 idler arm bushing...the "manufacturer"s stamp" is unknown to me..and i havent had any luck in diggin for more info either.

 

[M104-AMG]

Nice documentation. I've replaced two of these in the last 6-months: S124.092 and 036

I gave rubber bushing a quick wipe-down of Protectant 303 and I used my jack's bar (about 3-feet long) as a breaker-bar on the 1/2" drive ratchet.

Came off like butter.

neil

 

[RicardoD]

Yeah, I'm convinced if I had the right socket, and wasn't so impatient, I could have gotten that nut off. But then I would have missed out on all the sparks flying grinder fun!!

 

[emerydc8]

As i did say in the video...often stuff about quality is hearsay...and not first hand information and experience..so like in this case..i havent tried the URO part myself.

I would just as soon leave the old part on the car than install a URO part on it. Although, I am getting concerned that some of the once-reputable aftermarket brands are falling into the junk category.

 

[HowardK]

Would an impact gun help in removing he bolt?

 

[nocfn]

Not in my case....

 

[emerydc8]

Would an impact gun help in removing he bolt?

I'll let you know when the parts come. My plan is to soak it with PB Blaster first and then hit it with an impact driver on the first turn.

 

[Lowman]

Dont bother with an impact gun.you need a long extended wrench, and it will come loose pretty much straight away

 

[emerydc8]

Thanks. Did you have any problems getting a wrench on the bolt head on top or did you even need to hold it to loosen the nut below?

 

[nocfn]

I just had no luck with a breaker bar or an impact gun. No matter the size socket (points) or heat - she was too tight. I was on my back on ramps, but the last resort was to cut in my case.

 

[LWB250]

Breaker bar with a six foot piece of pipe slipped over it. Has worked for me many times, the only issue being able to get enough room to move it with the car on jack stands or ramps.

Dan

 

[gsxr]

If you can get an impact wrench on it, a high-torque 1/2" (or 3/4") should zip it right off. A weaker impact may not do anything.

Very much depends on how much power your impact wrench has. Mine Earthquake-brand air impact is rated something like 800 lb-ft peak and I have yet to encounter a fastener it won't break free. Next idler arm job, I'll give it a try.

 

[gerryvz]

Indeed, per LWB250, I've yet to find anything that a breaker bar with a three- or four-foot piece of pipe on it, won't break free.

 

[nocfn]

I will be 77 if I need to replace this again if past is prologue!

 

[Lowman]

Thanks. Did you have any problems getting a wrench on the bolt head on top or did you even need to hold it to loosen the nut below?

hey
no i had no problem getting the wrench on top,with the enclosed end of the wrench on the topside of the bolt..and a breaker bar as long as the torque wrench..about 60cm length.it was stuck ..but did not have an issue getting that sucker off.
With that said..i noticed a huge difference in loosening"torque" between the 201 one..and the 036 one..hence the tightening torque is very different.150 on the 036...and 120 on the 124 standard ones and 201"s.

 

[emerydc8]

Just got my parts today and did one car. It took about an hour from the time I walked into the garage to the time I was finished. I don't have much to add to Ricardo's and Lowman's excellent posts. Had I not known about maneuvering the large bolt and bushing in order to get the bolt head in and out, and having the bottom bushing removed to allow room at the bottom for the bolt thread side to maneuver, I would have thought that the right exhaust manifold would have to be removed. Thanks again guys.

[EDIT] I just replaced the second set and it only took about 30 minutes this time, since the tools were all out. Looking at the old bushings, they don't seem to have any more play than the new ones between the bushings and the long bolt. I'm wondering if they even needed to be changed. Maybe it's the rubber that goes bad, but the rubber seemed to be securely wedged in the tube so I don't see how that would make a difference. I guess it's too late now. It didn't seem to make any noticeable difference in the steering wheel play, not that there was much to begin with.

 

[RicardoD]

Yeah, I did not get a wow bit of difference (steering damper made a much bigger impact for me). I think if I do LCA, struts, and mounts, I may notice a change.

 

[emerydc8]

Looking at the rubber on these things -- and I'm presuming they are original 25-year-old parts -- it looks pretty good. Maybe I'll change the idler arms next. I need to do LCAs and tie rod ends on the '94, so that would be the time to do the idler arm too. What I thought was interesting about the MB idler arm is that there is no adjustment as there is on the domestics, which makes it simpler for amateur hacks like myself.

 

[Lowman]

Ric and Em..... Remember,if the idler arm bushing does not have "that much play" in it..you will not notice a huge difference.
If it doesnt have play..it does nothing to the steering feel if beeing replaced.
This part has to do with alignment accuracy on the right hand side,if it does have play,,the toe in on the right hand side will vary/shift as you ride

The steering damper does alot more to the "tighteness" of the steering feel..because if it beeing a component that controls the whole steering linkage

EDIT:if you do have a wandering car,,,two components is critical to check.One of them beeing the steering damper..the other one is the drag link.
The drag link i mention,,because it is often overlooked..as the play in it cannot be felt by doing the 3 and 9 o clock wiggle on the wheels.You will have to check it by pressing the balljoints together when mounted on the car.

 

[Lowman]

[EDIT]. Looking at the old bushings, they don't seem to have any more play than the new ones between the bushings and the long bolt. I'm wondering if they even needed to be changed. Maybe it's the rubber that goes bad, .

The play is developed between the tube that has the rubber "welded" on to it..and the center massive metal insert.It is a bearing without rollers basically.that is what develops play..and in most cases not the rubber.unless completely deterioated that is

So like mentioned..if the idler arm does not have any play to begin with..you wont feel any difference when replacing the part.

 

[emerydc8]

The play is developed between the tube that has the rubber "welded" on to it..and the center massive metal insert.It is a bearing without rollers basically.that is what develops play..and in most cases not the rubber.unless completely deteriorated that is

They must wear incredibly well because I checked the play in the new part versus the old and there seemed to be about the same amount of play. In any case, I'm glad I learned how to do this because the large bolt will have to come out in order to change the idler arm itself. I wouldn't change the tie rod ends without changing the center rod link. I'll have to check the availability on these parts. Hopefully the steering parts are still available.

[EDIT]
Looking at the EPC, it appears there's no reason to change the actual idler arm because there is no ball joint on the other end where it connects to the right tie rod and center link. It's just a hole. Does this wear out?

The price of the tie rod ends at mboemparts is about $85 each and the center drag link is $93.98, presuming (hoping) they are all still available.

 

[gsxr]

Jon, the idler arm itself should never require replacement unless damaged - it's not a wear item.

Lemforder (aftermarket) has a drag link but it's made in Turkey now, not Germany as in the past... cost is ~1/3 OE but I'm not sure if the kwality is the same anymore.

You generally want to replace the tie rods as assemblies, not just the ends. The cost isn't much more and it's nice to have an adjustment tube that isn't frozen. Lemforder (aftermarket) tie rod assemblies (both ends, plus adjustment tube) were still made in Germany for the last few I picked up at FCP earlier this year. The left (green) side is up to $71 now, right (black) side is still <$50. IIRC both are painted black now, maybe they ran out of green paint.

(Update: Lemforder tie rod assemblies are NLA as of 2021, and one or both sides of OE MB tie rods may also be NLA...)

 

[emerydc8]

Thanks, Dave. The last time I replaced the tie rods on my '95 I did the whole assembly so I will do that for the '94 as well. I didn't take a close look at the other end of the idler arm when I replaced the bushings, so I just presumed there was a ball joint there like the domestics.

I wonder how much QC Mercedes can accomplish with more and more of their parts made outside of Germany, and sometimes in third-world countries.

 

[Gatorblue92]

Huge thank you for making this how-to. Took me about 15 minutes to change the part out but the whole front suspension is already out so I had lots of room to work.

 

[geraniumtr]

Folks; this past weekend I successfully replaced the idler arm bushings on my 94 E320. This after several failed attempts. Not so easy on the M104 engine due to location of the exhaust pipes.
If anyone wants a detailed 'How To' just let me know and I'll write it up for you.

Regards,

Peter Weissman

 

[Seangbadee]

You can get the 24mm six-point deep socket at any Northern Tool store for $5.00. It has a number of uses beyond just this one, so it's a good one to buy.

Klutch Deep Socket Metric, 1/2in.-Drive, 6-Pt. | Northern Tool + Equipment

Unfortunately for those folks out West, Northern Tool stores are only in the Eastern USA.

Craftsman also has an impact socket that will work: https://www.craftsman.com/products/craftsman-24mm-lsr6pt-dp-1-2-00916086000

Cheers,
Gerry


Indeed....lowmania 4-ever!

I have a bit of problem with the removal of the bolt, even though loosening the nut/bolt assembly on my car (95 E320) was a breeze.
I cannot get the bolt out of the idler arm because there is a part of the exhaust system in my way.
Even if Icut the nut off, i still have to install the new bolt, and there is no way it can pass under the exhaust.
Any ideas?

 

[RicardoD]

All the photos / videos I have seen are on E500E. Obviously your 95 E320 is different. Sorry I can not offer much help.

 

[Seangbadee]

All the photos / videos I have seen are on E500E. Obviously your 95 E320 is different. Sorry I can not offer much help.

Thanks RicardoD

 

[geraniumtr]

I can help you as I did this job on my E320 recently. Should I PM you the How-TO ?

Peter Weissman

 

[Seangbadee]

I can help you as I did this job on my E320 recently. Should I PM you the How-TO ?

Peter Weissman

Yes, please.
Thank you

 

[geraniumtr]

Yes, please.
Thank you

I’m heading into work. After I get there I’ll write it up for you. You’ll need to spend $5 on a piece of steel pipe from your favorite big box hardware store. Peter

 

[Seangbadee]

I’m heading into work. After I get there I’ll write it up for you. You’ll need to spend $5 on a piece of steel pipe from your favorite big box hardware store. Peter

Thanks Peter

 

[bclifton]

I just finished this job and I felt guilty about it after reading this thread!

I had read this thread and watched a few videos dreading it. But this was one of the easiest jobs I've ever done - but only because I have a 300D with the OM603. There's almost 2 inches of clearance AFTER you pull the bolt through (in total, about 8 inches of wide open space above the bolt head, before you hit the exhaust). I don't know how many 124.133 folks there are - but at least I wanted to share some good news in case there are others (IIRC, @Bogeyman has the 87 300TD wagon, 123.193; and of course @gsxr).

The nut itself broke free after PB blasting the shit out of it. First couple of rounds with the impact gun did nothing. Sprayed it again, took a break. Then next try it came right off (just have to counter hold the top).

My bushings were so worn out that they almost fell out. Even the top one- I was able to grab the edges with my thumb and forefinger and pull up with only a little force and it came right out. In my case (and likely for the 300E, E320, etc), the part number for the rebuild kit is 124-460-00-19.

The only part that took a minute to sort out was putting the heat shield back on. There's basically a hole in the metal (on the body of the car) where you match it with the dimple in the heat shield strap. Then, when you put the heat shield on - you just put the notch in the shield through the end of the strap, pull down, and secure. It's not going anywhere after that!

 

[rayhennig]

In my case (and likely for the 300E, E320, etc), the part number for the rebuild kit is 124-460-00-19.

Hello all, from a 124.051 bloke.

Mine's a 300CE-24 and we have that repair kit in stock. Oddly, I have 2, both Lemfoerder but one made in Germany and one in China!!! We'll use the German one.

I understand that we may need to remove a heat shield. Yes? I've heard that it can be a bit of a b@st@rd - true?

Should we do it? Or should I leave it to the local garage that did the same job on the same car about 17 years and 250K Kms ago.

Minor wandering (to the right in France, to the left in UK) from straight ahead was completely cured.

As everything else is pretty good right now, I'm hoping that the lever bushing replacement will put the icing on the cake.

Am I on the right track?

Best to all.

RayH

 

[bclifton]

Hello all, from a 124.051 bloke.

Mine's a 300CE-24 and we have that repair kit in stock. Oddly, I have 2, both Lemfoerder but one made in Germany and one in China!!! We'll use the German one.

I understand that we may need to remove a heat shield. Yes? I've heard that it can be a bit of a b@st@rd - true?

Should we do it? Or should I leave it to the local garage that did the same job on the same car about 17 years and 250K Kms ago.

Minor wandering (to the right in France, to the left in UK) from straight ahead was completely cured.

As everything else is pretty good right now, I'm hoping that the lever bushing replacement will put the icing on the cake.

Am I on the right track?

Best to all.

RayH

With the inline 6, you might be able to do this without an issue. I would just hop under the car, locate the part, and see if you're able to reach your hand upward, where the bolt would go if you pulled it upward. In my case, that's when I noticed how much space I had.

When it's time for the job, yeah - you'll need to remove heat shield. Just one 10mm bolt and it should come off. With a proper impact gun (high torque) the nut on the bottom should break loose without any issues. Then you can try to get the bolt out through the top. If you get the top bushing loose, you should get some extra wiggle room. If you're not able to get this off, then I think that's a a good time to put it back together and bring it to the shop. Or go all the way with some of the tips shared earlier, where bolt access is difficult

 

[rayhennig]

I would just hop under the car

Yes, we'll do that when I'm next at my son's place with his 4-post lift.

Thanks for your comments and all the best.

RayH

 

[rayhennig]

I would just hop under the car,

We hopped yesterady afternoon.

We checked the idlier arm bushing. Looks new, no play. I think it was replaced new in 2017, about 70K Kms ago. Checked the torque too - 150 NM.

And we did not want to replace as the exhaust cat must be removed.

Still some mild shudder under braking having reinstalled the discs. Can only assume that my Chinese ATE discs are warped. Will drive for a few thousand Km and think again. More new discs, but from MB this time????????

But the biggest improvement in straight line stability follows changing the steering damper. The 7 year old Sachs one felt much the same as the brand new Chinese Bilstein replacement. But the car now cruises and stops in straight lines.

Satisfied with today’s progress but the shudder is still there. Poo.

And a warning to all. We fitted Textar pads that came with all the accessories, including the pins:

We fitted everything by the book.

But when my local man had the wheels off after my son and I had done our text book job, 3 of the 4 pins had popped out and there was a dreadful scraping noise.

And local man thought we were a couple of incapable idiots, “fookin’ 'ell” - he's from the North of England -, he said. And with good reason.

He tapped them all back and said that all should be well.

Fast forward a few weeks to yesterday and local man and I are still investigating shudder.

AND ANOTHER PIN HAS POPPED OUT.

The locking collar on the pin is very poor quality.

My son’s going to MB tomorrow for a new stock of pins.

So, no resolution of the shudder issue, but progress in straight lines.

RayH

 

[emerydc8]

I’ve had vibration issues while braking a number of times and on every occasion a new set of factory rotors fixed the problem.

 

[rayhennig]

I’ve had vibration issues while braking a number of times and on every occasion a new set of factory rotors fixed the problem.

I think it may come to that.

R