Idler Arm Bushing question 126 - PeachParts Mercedes-Benz Forum

Proctor750 · #1 08-28-2022, 06:49 PM

I installed the genuine Mercedes replacement and torqued to 134 ftlbs.

The arm moves freely but there is light resistance. Is this normal?

Does this affect return to center?

JHZR2 · #2 08-28-2022, 07:16 PM

Isn’t this one that needs to be torqued with the car on the ground, suspension weighted? Is that how you did it?

Proctor750 · #3 08-28-2022, 07:38 PM

Quote:

Originally Posted by JHZR2

Isn’t this one that needs to be torqued with the car on the ground, suspension weighted? Is that how you did it?

I believe that is only the upper and lower control arms and stabilizer ends.
I dont see how that would impact the idler arm in any way.

Graham · #4 08-28-2022, 09:15 PM

Quote:

Originally Posted by Proctor750

I installed the genuine Mercedes replacement and torqued to 134 ftlbs.

The arm moves freely but there is light resistance. Is this normal?

Does this affect return to center?

I don't have access to W126 manual, but my 107 and 123 both specify 120NM torque. Which is only 89 ft.lb. Perhaps the 126 uses a heavier bolt? You don't have to have wheels on ground to torque that bolt!

The bolt torque should not affect the resistance to turning. It just compresses the two internal metal sleeves against each other. If the end bearings do get compressed, then you will get resistance. That should not happen. If it does, a shim washer can be inserted between the internal sleeves. There is supposed to be a small amount of vertical slack.

I initially bought an aftermarket Lemfoerder kit. It was simply just wrong. I had to add 5 or 6 shims before it would turn freely. I returned it and bought a genuine kit that fitted and worked perfectly.

If the idler bearing is tight, it will affect centering. You will get what they call memory steer. Believe me, I had that until I replaced the bearing kit.

Proctor750 · #5 08-29-2022, 12:54 AM

Quote:

Originally Posted by Graham

I don't have access to W126 manual, but my 107 and 123 both specify 120NM torque. Which is only 89 ft.lb. Perhaps the 126 uses a heavier bolt? You don't have to have wheels on ground to torque that bolt!

The bolt torque should not affect the resistance to turning. It just compresses the two internal metal sleeves against each other. If the end bearings do get compressed, then you will get resistance. That should not happen. If it does, a shim washer can be inserted between the internal sleeves. There is supposed to be a small amount of vertical slack.

I initially bought an aftermarket Lemfoerder kit. It was simply just wrong. I had to add 5 or 6 shims before it would turn freely. I returned it and bought a genuine kit that fitted and worked perfectly.

If the idler bearing is tight, it will affect centering. You will get what they call memory steer. Believe me, I had that until I replaced the bearing kit.

I believe 126 torque spec is 180nm or ~134ft lbs. It was a bear to unbolt and it moved much more freely with the old bushings.

So I could add another couple of mm shim to the bottom where the bottom nut attaches? The top is just a dust shield and washer.

I did see various thickness bottom shims available somewhere before..

But it should be completely loose with 0 stiction?

What's frustrating is that I bought the Mercedes Genuine kit, not the Lemforder 3mm too short stuff mentioned here: https://www.benzworld.org/threads/idler-arm-bush-failed-quickly.3058754/

I suppose I will need to shoot for a lower torque or else find some way to shim between the 2 inner sleeve halves as .5mm end float is permissible

JHZR2 · #6 08-29-2022, 03:40 AM

Quote:

Originally Posted by Proctor750

I believe that is only the upper and lower control arms and stabilizer ends.
I dont see how that would impact the idler arm in any way.

Sorry… jet lag and not thinking straight. Lol.

Proctor750 · #7 08-29-2022, 12:50 PM

Is it possible that it will wear in? Or should it swing completely freely immediately? I just don't understand how the new in box factory piece has any resistance at all. It's not much but it's nothing like the old ones which were also genuine.

UPDATE:
I checked the manual and indeed it's 120NM... I have no idea why I thought it was 180NM now and the old one had to have been completely overtorqued yet worked fine. So perhaps the lower torque might help but I may need to beat the 2 halves back out some before attempting to retorque. They could be mashed together or something.

And the additional shims they mention are indeed for the bottom nut. I wonder if my old one is thicker - I will need to bust out the calipers.

Graham · #8 08-29-2022, 01:57 PM

If the idler is tight, the shim that is needed goes between the two inner bushings. Perhaps you won't need any if proper torque is used.

As I understand it, the washer that goes under the nut or idler arm is to adjust height relative to pitman arm. That shouldn't really affect the freedom to rotate.

With OE bearing kit you shouldn't have needed the inner shim. I bought thin shim/spacer washers at Home Depot when I was trying to overcome excessive friction in the Lemfoerder bushing. The shim goes where arrow points in pic below:

Proctor750 · #9 08-29-2022, 03:48 PM

Quote:

Originally Posted by Graham

If the idler is tight, the shim that is needed goes between the two inner bushings. Perhaps you won't need any if proper torque is used.

As I understand it, the washer that goes under the nut or idler arm is to adjust height relative to pitman arm. That shouldn't really affect the freedom to rotate.

With OE bearing kit you shouldn't have needed the inner shim. I bought thin shim/spacer washers at Home Depot when I was trying to overcome excessive friction in the Lemfoerder bushing. The shim goes where arrow points in pic below:

Agreed, I will undo the bolt and hammer each bushing back out a little then retorque to 120nm.

Although putting the shim between the halves makes sense to me, the mercedes diagram points to the 2.5 and 3mm interchangeable shims going under the Nut.

There is also the ability to change the thick washer above the dust shield at the top for helping with centering the ball point position. But no mention of having one between the two halves.

Graham · #10 08-29-2022, 04:28 PM

Quote:

Originally Posted by Proctor750

Although putting the shim between the halves makes sense to me, the mercedes diagram points to the 2.5 and 3mm interchangeable shims going under the Nut.

As mentioned earlier, those thicker shims under nut are for height adjustment. Not the same purpose at all as the thin shim (which you should not need anyway)

On my car, I couldn't see how changing the idler bushings could change the relative height of idler and pitman, so I never considered those thicker shims.

Proctor750 · #11 09-01-2022, 10:59 AM

Well I backed the nut off entirely and it swings totally free with 0 resistance. I torqued it to exactly 120ft lbs and there's still slight resistance as before.

I undid the bold again and hammered the bushings out a tad then re-torqued and the exact same resistance applies. I even tried tightening to about 60NM first and it still had the same resistance.

So basically any torque on the nut at all produces this slight resistance. It's not much and perhaps the wheels/suspension will overpower it but it's definitely not floppy like it was with the old bushings.

It is the nut/bolt and washers which rotate and not the bushings which I believe is correct but there is just enough resistance that if you let go of the pitman arm it doesn't swing down on it's own weight. It is smooth and you can move it with your pinky which is why I think the wheels/suspension should still overpower it and perhaps wear them in?

I'm just going to go with it and see what happens. Not much else I can do at this point.

Sugar Bear · #12 09-01-2022, 11:48 AM

Slight resistance should be fine, I'd expect some not zero. If there isn't any memory steer and the car finds on center without fail...drive on!!!

If you can find a GOOD alignment shop e.g., a frame shop the difference when everything is dialed in is amazing.

Good luck!!!

Graham · #13 09-01-2022, 02:02 PM

Quote:

Originally Posted by Proctor750

So basically any torque on the nut at all produces this slight resistance. It's not much and perhaps the wheels/suspension will overpower it but it's definitely not floppy like it was with the old bushings.

It is the nut/bolt and washers which rotate and not the bushings which I believe is correct but there is just enough resistance that if you let go of the pitman arm it doesn't swing down on it's own weight.

Actually, when clamped together by the bolt torque, the inner metal sleeves, the end washers and the bolt are supposed to rotate in unison within the rubber sleeves.

The torque on the nut should not make any difference to the turning resistance if the overall face to face length of the two inner sleeves is correct. If that distance is too short, then the end washers put frictional force on the bearing faces within the rubber sleeves.

If interested, this is quite a long thread describing my learning experiences with a similar idler arm. A second problem I found and addressed, was that the rubber inserts could rotate within the chassis tube. They should not. They should be a tight fit in the tube.
https://www.benzworld.org/threads/idler-arm-bushing-replace.3059235/

Proctor750 · #14 09-01-2022, 02:21 PM

Quote:

Originally Posted by Graham

Actually, when clamped together by the bolt torque, the inner metal sleeves, the end washers and the bolt are supposed to rotate in unison within the rubber sleeves.

The torque on the nut should not make any difference to the turning resistance if the overall face to face length of the two inner sleeves is correct. If that distance is too short, then the end washers put frictional force on the bearing faces within the rubber sleeves.

If interested, this is quite a long thread describing my learning experiences with a similar idler arm. A second problem I found and addressed, was that the rubber inserts could rotate within the chassis tube. They should not. They should be a tight fit in the tube.
https://www.benzworld.org/threads/idler-arm-bushing-replace.3059235/

I think we are saying the same thing - the rubber "inserts" do not move and should not move. The nut/bolt/washer assembly are what rotate. Even if I back the nut off the spacer entirely it they all still move together. So I think the function is correct but perhaps this newer assembly just has a tad more friction than the old one. I should have put the digital calipers on old and new to compare but we shall see how it goes.

I'm checking that thread out now - I believe I have read some of it back when I first ordered the replacement kit which is why I chose to go with Mercedes genuine so I have you to thank for that.