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Premium Member
1986 420SEL/1995 E300D/4 BMW’s/2 Vanagon’s
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1,026 Posts
Discussion Starter #1
The guide rod connects between the the lower control arm and the carrier bushings on the front of the car. Adjustment of the guide rod controls the caster of the front wheels. There are bushings on either end of the guide rod. The rear is the idler arm bushing, and the front is the guide rod bushing. This DIY focuses on the front bushing.

Be aware that I have found several names for these parts on the web: guide rods, idler arm, brake brace etc. I am using the term guide rod.

The front guide rod bushings are trapped inside the lower control arm underneath the spring perch. I don't think this job can be done without removing the spring, however, I could be wrong. I went ahead and removed it. For most people, the toughest part of this job might be removing the spring. If you have a good plate style spring compressor, removing the spring is actually pretty easy. Once you’ve done that, the rest of this job is cake.

Here is a photo of the guide rod bushing location with everything in place. See circled part:



Getting the spring removed:



Spring removed:



There are three bolts the hold in the spring perch. They are 13mm. Here is the spring perch removed and you can clearly see the bolt for the guide rod bushing. This bolt is 19mm with a 19mm nut on the bottom.



Guide rod bushing removed:



Here is the bushing repair kit. Mercedes calls it the “brake bracing to control arm” repair kit in the EPC. It is part number 123 330 14 75. It comes with the two rubber bushing (top and bottom), two metal coned shaped washer thingys (top and bottom) and a new nut and bolt:



When putting in the new rubber, notice that there is a cutout on the bottom that is positioned over the guide rod itself. Without making sure this lines up, the bushing will not seat right:



Bushing in place:



Finally, with everything in place:



That’s it. Just put everything back together and you are done!
 

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Premium Member
1986 420SEL/1995 E300D/4 BMW’s/2 Vanagon’s
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1,026 Posts
Discussion Starter #3
Problem is, I also did my steering gearbox while I did this (working on that DIY right now), however, I don't think these made that huge of a difference. They were visibly worn comparing them to the new ones, but not loose on the car.
 

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93 190E 2.6; 82 300 SD Turbo
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1,686 Posts
Did you do the rear bushing on the other side of the guide rod? I'm considering doing those on my 420SEL.

Not sure if the spring has to come out to do those or not..
 

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Premium Member
1986 420SEL/1995 E300D/4 BMW’s/2 Vanagon’s
Joined
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1,026 Posts
Discussion Starter #5
I actually did the entire front suspension in the last month or so. I did do the rear guide rod bushings as well. Since I was redoing the entire front end, I had the springs and shocks out. I had taken off the entire carrier bearing with the guide rod attached. With that said, you *might* be able to do the rear bushing without removing the spring. You could unbolt and drop the carrier bearing, unscrew it from the guide rod and replace it on the bench. I would also do the carrier bushings at the same time if I were doing this. What would make me nervous is that you would no longer have the guide rod keeping the spring from moving the LCA around. I think it could be dangerous but I am not an expert here. Perhaps someone else can chime in.
 

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1991 300SE W126 Collector owned, maintained 90k mi
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177 Posts
Idler arm bushing

I actually did the entire front suspension in the last month or so. I did do the rear guide rod bushings as well. Since I was redoing the entire front end, I had the springs and shocks out. I had taken off the entire carrier bearing with the guide rod attached. With that said, you *might* be able to do the rear bushing without removing the spring. You could unbolt and drop the carrier bearing, unscrew it from the guide rod and replace it on the bench. I would also do the carrier bushings at the same time if I were doing this. What would make me nervous is that you would no longer have the guide rod keeping the spring from moving the LCA around. I think it could be dangerous but I am not an expert here. Perhaps someone else can chime in.
The idler arm bushing is the one opposite the steering knuckle and held in place with the large bolt. It acts as a rotating point for the right side steering geometry. The actual guide rod bushings, the large ones at the rear of the guide rod can be replaced without spring removal. Make sure you count the rotations to get the unit close to the previous setting. I have also found it to be a good idea to run the new long bolts into the retaining nuts(the ones with the straps). If the nuts break off the straps within the body of the car its a PIA. I usually add more spot welds to the nut/strap. Also the large bushing may have to be pressed out and can be done at home with some creative measures. Installing the new one should be done with KY jelly and not a petroleum base. The inside bore usually corrodes so a wire wheel on a drill or sandpaper to smooth the bore is a wise idea.
 
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