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Pelican Technical Article:

Idler Arm Bushing Replacement

Kerry Jonsson

Time:

3 hours3 hrs

Tab:

$150

Talent:

***

Tools:

19mm, 24mm wrenches and sockets with ratchet

Applicable Models:

Mercedes-Benz R129 (1990-02)

Parts Required:

Idler arm

Hot Tip:

Lift the right side of the engine up to clear the fastener

Performance Gain:

Improved handling and reduced vibration

Complementary Modification:

Change the center link at the same time

As you turn your steering wheel when you drive you are turning a shaft that runs down the steering column. This shaft is attached to the power steering gearbox. The power steering gearbox converts the twisting motion of the steering wheel shaft to the back and forth motion for the Pitman Arm. The Pitman Arm is attached to the center link. The Pitman Arm moves the center link either left or right depending on the direction you want to turn. The Pitman Arm holds the left side of the center link steady as it moves back and forth. It is the job of the idler arm to hold the right side of the center link and inner tie rod for the right side. This keeps the left and right wheels in proper alignment while turning the steering wheel from left to right. Mercedes Benz uses a frame mounted bushing to act as the idler arm. When you service this part you will not be replacing the idler arm but the idler arm bushings. In order to do that you will have to disassemble the idler arm assembly. Over time these bushings can wear out and allow the right side center link and inner tie rod end to be slightly out of alignment with the steering linkage on the left side of the vehicle. This will cause steering wheel vibration, a knocking noise when changing direction and uneven tire wear.

Lift and support your vehicle, after installing those stylish safety glasses on your noggin. See our tech article on lifting and supporting your vehicle. While you are under your vehicle have an assistant turn the steering wheel back and forth 45° with the ignition key on but the engine not running. Watch the center line link and inner tie rod end and see if you can see the idler arm move around in the frame mount. If the bushings are worn, you will notice the play between them. In this tech article I will go over the steps to replace your idler arm bushings.

ThisPicture illustrates underneath the car looking up at the right side by the back of the lower control arm.
Figure 1

ThisPicture illustrates underneath the car looking up at the right side by the back of the lower control arm. Using a 24 mm wrench to hold the top of the fastener (yellow arrow) loosen the 24mm fastener (green arrow) hidden behind the sub-frame mount. I have put a long 24mm socket and ratchet on it.

here I am looking at the right side wheel well at the inner tie rod end.
Figure 2

here I am looking at the right side wheel well at the inner tie rod end. Remove the 19mm fastener for the inner tie rod end.

Remove the 19mm fastener (green arrow) that attaches the right side of the center link.
Figure 3

Remove the 19mm fastener (green arrow) that attaches the right side of the center link.

Working back at the right side of the center link, use a splitting fork to separate the center link from the idler arm.
Figure 4

Working back at the right side of the center link, use a splitting fork to separate the center link from the idler arm.

Using a puller remove the inner tie rod end from the idler arm.
Figure 5

Using a puller remove the inner tie rod end from the idler arm. You can also use a splitting fork or hammer on the joint until the tie rod end pops out.

The bolt is too long to be pulled out of the idler arm mount and makes contact with the exhaust manifold (green arrow).
Figure 6

The bolt is too long to be pulled out of the idler arm mount and makes contact with the exhaust manifold (green arrow). At this point some people cut off the head of the bolt with a hacksaw and pull the bolt out through the bottom. A new bolt usually comes in the repair kit. If you do this you can simply install the bolt through the bottom of the idler arm mount and then tighten the fasteners.

If you do not want to use this method you can remove the two bolts recessed in the sub-frame (green arrows) to loosen the motor mount.
Figure 7

If you do not want to use this method you can remove the two bolts recessed in the sub-frame (green arrows) to loosen the motor mount. Then using a jack lift up the right side of the motor from the oil pan to gain more clearance. Use a block of wood to protect the oil pan from the jack.

You now have more clearance to remove the bolt (red arrow).
Figure 8

You now have more clearance to remove the bolt (red arrow). If the bolt is stuck, you can use a drift and tap the bottom of it to slide it past the exhaust manifold if it is still touching. Don't lose the washer (green arrow) at the top of the idler arm, it protects the bushing from the heat that emanates from the exhaust.

Working at the top of the idler arm mount, tap out the bushing (green arrow) in the direction of the blue arrow.
Figure 9

Working at the top of the idler arm mount, tap out the bushing (green arrow) in the direction of the blue arrow. A drift punch and a hammer should be sufficient to remove it.

Working from the top of the idler arm mount, insert a drift and push the lower bushing (green arrow) in the direction of the blue arrow to remove it.
Figure 10

Working from the top of the idler arm mount, insert a drift and push the lower bushing (green arrow) in the direction of the blue arrow to remove it. Installation is the reverse of the removal procedures. Insert the upper and lower bushings and install the fastener. Tighten it down and install both the inner tie rod end and center link.

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Comments and Suggestions:
Robert M Comments: Would you need to do an alignment after this service?
February 29, 2016
  Followup from the Pelican Staff: The suspension angle may change due to the new part. - Nick at Pelican Parts  

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