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W140 steeering idler arm bolt/nut removal.

6K views 27 replies 5 participants last post by  Joe-V12 
#1 ·
For whatever reason the nut to undo the bolt on the idler arm on my S500 was tight, and I mean tight. Tight to undo and tight to work on. It's 22mm across flats and being so close to the subframe that access with a 1/2" drive 22mm socket and breaker bar is not really possible.

I was progressively rounding the nut off with normal ring spanners and 12 sided sockets. I sourced a quality 22mm 1/2" drive impact socket with 6 sides, lathed the diameter down, shortened it and tapered the end of it. I also grinded down and rounded the breaker bar, all required to fit on the nut properly in the limited room available.

Working under the car I still needed pipe on the end of the breaker bar, doubling the length to get enough leverage. Up top there is plenty of room to hold the bolt head with a 22mm ring spanner.

For anyone looking to tackle this job be prepared with something like this:
 

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#3 ·
Clearance up the top is no problem, just remove the cover from the starter motor.

It was the clearance around the nut down the bottom that I had issues with, maybe most people don't have the nut so tight.
 
#4 · (Edited)
Hi Joe,
I had to cut my bolt, was supper tight. Used 22mm wrench (12 pts) and rounded it...

But, I will have to correct your post (don't know if this was the S600 or the S420).
With the M120 setup, there will be almost no room to remove the bolt from the top. Engine has to raised quite a bit for the bolt to clear the exhaust manifold.

I think I've got a picture showing what one should see when a bunch of stuff is removed from the engine bay.

Steve
 
#6 ·
The OP and my experience so far is with my S500.

I do plan on doing the S600 next. If I need to raise the engine I will do engine mounts at the same time.
 
#7 ·
Just some finer details, pic is of new bolt and nut installed on my S500.

Red line is subframe access limitation which prevents the bolt from being installed upside down, probably a safety feature so the bolt can't come loose and fall out! This also limits access with a socket and breaker bar if a ring spanner doesn't achieve what's required as in my case.

Yellow is length for socket and breaker bar including distance to fit the socket onto the nut. It looks like a lot in the photos but it's really not.
 

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#10 ·
Can move the idler arm up/down. Front wheel on passenger side can be moved while drivers side can not. It will scrub the front tires even after an alignment and steering feels loose, wanders, and tramlines, even with the steering box adjusted for no slack. Check also for loose/worn balljoints.
 
#12 ·
Can move the idler arm up/down. Front wheel on passenger side can be moved while drivers side can not. It will scrub the front tires even after an alignment and steering feels loose, wanders, and tramlines, even with the steering box adjusted for no slack. Check also for loose/worn balljoints.
That indicates it is warn, up/down is vertical movement! :D

Man you will love the steering after you replace it!
 
#13 ·
Hm, ok. I was under impression that it may have a little movement along the bolt. Idler arm itself is not moving really, but if i insert long scredriver between tube of the idler and the frame i can slide the tube along the bolt 1-2mm. It does not transfer into ablity to move arm itself vertically (worn bushings). Can new one be slid abit along the bolt?
 
#14 ·
I just replaced my steering joints today: Idler arm bushing, tie rod assemblies and center/drag link.

Actually all the parts except for the idler arm bushing was not worn although new obviously tighter and feels better. Hard to believe with almost 200k miles.

The idler arm previous has some play that I could feel and hear when pushing/pulling up and down on the arm.

Post replacement now perfect and good as new...so glad I changed it.

Joe you did have me a bit worried about that idler arm nut,.,,,and right you were so thanks much for the heads up. I did not do anything as fancy as your lathe operation of the 6 point socket but this worked for me.....
I held the nut with a box wrench and used a 6 point socket on the bolt head with long extensions..... man oh man was that tight but I did it and it worked.

Seth
 
#15 ·
Shimshon prob a bit more room in the I6 engine bay compared to the V models.

Alter why on earth would movement along the bolt be normal? It lets the passenger side wheel move by itself separate from the drivers side, not ideal. OK I don't know how hard you are levering on it with a screwdriver, but as I have stated, vertical movement indicates the bush is warn.
 
#16 ·
Confirmative, on my way to change bushings :)
I guess next weekend i'll have steering box resealed, drug link, idler bushings. Then i'll have no old parts left anywhere in front suspension.

Although i must say i was not expetind to do every single pc at 51k... :( i have no clue how people are putting 200k on these cars... All seals and rubber on my front is trashed, i guess the car was not designed for AZ heat.
 
#18 ·
Thanks to everyone on this topic!
Just did drug link and idler bushings. Pretty simple job. The only annoyences are heatshield bolts around starter, and torque of the idler nut. But box wrench worked for me ok, few swings of the 4lbs hammer and nut started to go :)
Finished idler did not have any play along the bolt, so if yours has 1-2mm (as my old did) it is not terrible, but bushings are in about to go south.

Did anyone do re-seal of the steering box?
I wonder if removing of the pitman arm is hard? It has compression bolt at the end, so in theory i should not need any remover? I have one (harborfreight) but it is too big for the location. I'd have to modify it to make it fit.
 
#19 ·
Found this thread in the search. Yeah!

Just found out that my 1994 S420's idler arm is toast, which is why the passenger side tire got completely wiped out in a very short period of time.

I am just looking for validation here:

So based on reading the thread, I can expect that the nut on the bottom of the idler arm bushing bolt will be a major PITA to turn and possibly access? Do any of you that have done this think it's due to environment or just the locking insert in the nut?

I ask because this car has spent it's life in the South, never seeing snow or any other crud. Undercarriage is very clean. Also, since I know this is going to be done on Tuesday when my parts arrive, would it help to hit the nut with some penetrating oil, such as Kroil?

Thanks,

Dan
 
#20 ·
This is how I chose to successfully complete the job:
I was able to get a box wrench on the nut to hold it but no ability to spin or loosen the nut due to frame interference.
I was able to have ample access to the topside bolt with a socket, extension, breaker bar.
Having assistant hold the nut I was able to get the job done topside
Reverse for installation.
Utilized OEM lemforder part for replacement.
No longer has any play in idler arm....good as new now.

Hope that helps.

Seth
 
#22 ·
Sure does, Seth.

I've done these on a number of older models, but never on a W140. I know it will be tight, but I've got a helper and can have them below while I get the top with the extension(s) and breaker bar.

I'm going to assume there is probably a frame member or something substantial the wrench can hit up against while I'm turning from above?

Thanks!

Dan
 
#23 ·
Idler arm is super easy on w140. Just make sure you have balljoint separator to remove steering links out of the way.

Steering box is pain, if you want to get it out and reseal. Lower seal can be done easier, but is not complete fix. Pitman arm is super easy to remove, no need to use puller. However you have to maneuver it to remove the bolt locking it in place. It has very strange positioning making it difficult.
 
#26 ·
Update

The kit is coming tomorrow in UPS, so I got under the car today to get things ready.

The nut and bolt are both 21mm, not 22mm.

With a breaker bar stuck in the other end of a wrench I was able to break the nut loose. I had a ratcheting closed end wrench I was able to use to hold the bolt head while I unscrewed the nut with my combination wrench - pretty easy once it was broken loose.

In anticipation of removing and replacing the bolt, I removed the starter heat shield, which again wasn't bad at all once the fasteners were broken loose.

Rolled it back out of the garage and parked in anticipation of replacement when the parts arrive tomorrow.

I Stil see no need for removing anything from the idler arm itself. It appears that by just lifting the bolt out I'll be able to move the arm and sleeve it's attached to in order to get the old bushings out and install the new ones.

Dan
 
#27 · (Edited)
Swapped out the bushings and bolt tonight. Some observations:

1.) I did it without assistance, so I didn't go the route of using a really long extension and universals to get a socket on the bolt from above.

2.) I removed the starter heat shield. This is a must to clear the bolt.

3.) I pulled the lower bushing out with a pair of pliers. Minimal effort. Top bushing wasn't as easy, I used a long screwdriver, braced the idler arm with my hands, and tapped on the screwdriver with a small mallet. Took a few taps, but it came out without too much effort. Both bushings had the ribs worn down almost flat, the metal bushings weren't sloppy but they weren't super tight with the bolt, either.

4.) I used the old bolt, nut, and a stack of washers to press (pull) the new bushings into the idler arm tube. Didn't take a lot of effort.

5.) Lining up the new bolt, heat shield and bushings took some time. be really, really careful, as with the starter heat shield removed, the wires are all exposed. This means if you're not careful with the bolt while you're aligning everything you might make some sparks! (Don't ask me how I know this.)

6.) Doing this from below using wrenches is taxing, to say the least. You don't have a lot of room to work with, meaning you can't get a lot of rotation with the wrench. I used a wrench above to hold the bolt, and a wrench below to run the nut down until tight.

All in all not a difficult job, just time consuming and fiddly considering the operation itself.

9:00 am appointment with the alignment rack, and the car is back on the road.

Dan
 
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