R&R Guide Rod Bushings
09-06-2006, 12:40 PM
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'86 560SEC, '92 400E, '83 300TDT, '05 ML63
R&R Guide Rod Bushings
W126 folks FYI:
My '86 560 SEC had turned into a one-man band when I drove over bumps or turned corners - the front end would groan, squawk, grunt, clunk, and squeak.
I replaced all the usual suspects - bushings, control arms, b-joints, even the sway bar bushings. No improvement.
That left only one possibility - the dreaded and highly feared Guide Rods.
I have read here and elsewhere, as well as in the M-B W126 manual that changing out the guide rod bushings required an array of "Special" tools made by magical gnomes in Dusseldorf, and a degree in advanced astrophysics. Evidently failure to properly follow the precise micrometer adjustments associated with the guide rods would cause your front end to fail completely, with a loud noise, while driving at top speed in rush hour traffic with several elderly nuns as passengers.
This, as it turns out, is not the case.
Here's how I did it:
You will need to remove the springs. Big deal - you have a Mercedes spring compressor, so use it.
Remove the spring mounting pad - three #13 bolts hold it onto the lower arm.
Remove the cross bar between the guide rod mounts; 6 #19 bolts.
Measure the distance from the guide rod boss to the start of the guide rod. Mark where you measured from with chalk. Write the measurement in chalk on the inside fenderwell so you don't forget.
Remove the bolt and bushing from the lower control arm that holds the forward end of the guide rod. You will replace this with a new kit you bought from Rusty.
Remove the 2 #19 bolts from the guide rod mount. Take it over to your work bench.
Take off the back plate (4 allen bolts) from the bushing housing.
Loosen the #13 nut on the rod clamp. Put a #17 wrench on the threaded rod and screw the guide rod off.
I used two standoffs from my bearing puller set, about 4" long, which screwed into 2 threaded holes in the guide mount for the backing plate. This allows you to set the mount level on the floor. Put a 10" length of about 1" pipe over the threaded rod.
Hit the pipe really hard with a 20-pound sledgehammer. This is a "Special" tool, available only from TSC or a large neghbor.
The bushing will pop out after a couple of hits, if you are manly. If you are not manly, get your wife to hit it.
Laugh at the old bushing, and throw it away, or keep it to show people. It will be all rusty and corroded. The rubber boot went away a long time ago.
Clean up the rusty, corroded mount. Clean down to aluminum, or the new bushing you bought from Rusty will not go in.
Put a little silicone brake grease on the new bushing and the inside wall of the mount. Petroleum-based grease or oil will attack the rubber, and that would be bad.
Hold a section of 2X4 on the back of the bushing and whack it with a 4-lb brass hammer that you liberated from your workplace 25 years ago, and is the most useful tool you own.
Hit the wood carefully so that the bushing goes in easily and squarely. Hit at alternating 180 degree points and check how the bushing is going in after every whack.
The metal bushing will end up flush, or nearly (0.7mm) flush with the mount. Oh, don't forget to line up the rubber split in the bushing with the water drain hole on the mount. ...probably should have mentioned that earlier.
Put the new rubber maltese cross on the back of the bushing and bolt the cover back on. Run the guide rod onto the new threaded rod up to about your measured point. Don't tighten the clamp yet.
Now put everything back together in opposite order of the way it came off. There are new captured nuts for the mounts in the kit. New bolts with threadlock for the crossmember.
Put the springs back in. While you are at it, you can trim the spring rubber pad down about 5mm to lower your ride height a little bit. Use a bayonet and saw the same amount off the top off the pads. Slip and cut the crap out of your middle finger. Don't get stitches, even though you need them, because your car is obviously up in the air and you are home alone. Bleed all over the garage floor. Dogs will clean it up later.
Later, with large bandage on middle finger, put car back together with one hand. Check your measurement again, once everything is buttoned up. If you need to adjust, put a wrench on the flats of the threaded rod and turn in or out until you are right. Then tighten the clamp on the rod, so it won't move.
Drive car (let it down off the jacks, first). Silence. Amazing. Alignment is perfect - wasn't changed at all.
Who knew those damn things could make so much noise?
Best Regards,
e.
.::.
My '86 560 SEC had turned into a one-man band when I drove over bumps or turned corners - the front end would groan, squawk, grunt, clunk, and squeak.
I replaced all the usual suspects - bushings, control arms, b-joints, even the sway bar bushings. No improvement.
That left only one possibility - the dreaded and highly feared Guide Rods.
I have read here and elsewhere, as well as in the M-B W126 manual that changing out the guide rod bushings required an array of "Special" tools made by magical gnomes in Dusseldorf, and a degree in advanced astrophysics. Evidently failure to properly follow the precise micrometer adjustments associated with the guide rods would cause your front end to fail completely, with a loud noise, while driving at top speed in rush hour traffic with several elderly nuns as passengers.
This, as it turns out, is not the case.
Here's how I did it:
You will need to remove the springs. Big deal - you have a Mercedes spring compressor, so use it.
Remove the spring mounting pad - three #13 bolts hold it onto the lower arm.
Remove the cross bar between the guide rod mounts; 6 #19 bolts.
Measure the distance from the guide rod boss to the start of the guide rod. Mark where you measured from with chalk. Write the measurement in chalk on the inside fenderwell so you don't forget.
Remove the bolt and bushing from the lower control arm that holds the forward end of the guide rod. You will replace this with a new kit you bought from Rusty.
Remove the 2 #19 bolts from the guide rod mount. Take it over to your work bench.
Take off the back plate (4 allen bolts) from the bushing housing.
Loosen the #13 nut on the rod clamp. Put a #17 wrench on the threaded rod and screw the guide rod off.
I used two standoffs from my bearing puller set, about 4" long, which screwed into 2 threaded holes in the guide mount for the backing plate. This allows you to set the mount level on the floor. Put a 10" length of about 1" pipe over the threaded rod.
Hit the pipe really hard with a 20-pound sledgehammer. This is a "Special" tool, available only from TSC or a large neghbor.
The bushing will pop out after a couple of hits, if you are manly. If you are not manly, get your wife to hit it.
Laugh at the old bushing, and throw it away, or keep it to show people. It will be all rusty and corroded. The rubber boot went away a long time ago.
Clean up the rusty, corroded mount. Clean down to aluminum, or the new bushing you bought from Rusty will not go in.
Put a little silicone brake grease on the new bushing and the inside wall of the mount. Petroleum-based grease or oil will attack the rubber, and that would be bad.
Hold a section of 2X4 on the back of the bushing and whack it with a 4-lb brass hammer that you liberated from your workplace 25 years ago, and is the most useful tool you own.
Hit the wood carefully so that the bushing goes in easily and squarely. Hit at alternating 180 degree points and check how the bushing is going in after every whack.
The metal bushing will end up flush, or nearly (0.7mm) flush with the mount. Oh, don't forget to line up the rubber split in the bushing with the water drain hole on the mount. ...probably should have mentioned that earlier.
Put the new rubber maltese cross on the back of the bushing and bolt the cover back on. Run the guide rod onto the new threaded rod up to about your measured point. Don't tighten the clamp yet.
Now put everything back together in opposite order of the way it came off. There are new captured nuts for the mounts in the kit. New bolts with threadlock for the crossmember.
Put the springs back in. While you are at it, you can trim the spring rubber pad down about 5mm to lower your ride height a little bit. Use a bayonet and saw the same amount off the top off the pads. Slip and cut the crap out of your middle finger. Don't get stitches, even though you need them, because your car is obviously up in the air and you are home alone. Bleed all over the garage floor. Dogs will clean it up later.
Later, with large bandage on middle finger, put car back together with one hand. Check your measurement again, once everything is buttoned up. If you need to adjust, put a wrench on the flats of the threaded rod and turn in or out until you are right. Then tighten the clamp on the rod, so it won't move.
Drive car (let it down off the jacks, first). Silence. Amazing. Alignment is perfect - wasn't changed at all.
Who knew those damn things could make so much noise?
Best Regards,
e.
.::.
10-01-2006, 06:11 PM
#2
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85 300SD, 80 280SL, 90 300TE 4Matic, 90 300D 2.5 Turbo, 91 300E 4Matic, 92 300D 2.5 Turbo, 87 300TD
I recently changed mine but did not remove the springs.
I jacked up the car on to stands, then used the floor jack to raise the lower control arm.
I then dropped the guide rod bearing sub-assembly and rotated if off the guide rod.
I next changed out the guide rod bearing from its assembly and then rotated it back on the guide rod.
The important thing to do with this procedure is to make sure the lower control arm is slightly lifted and stable by the floor jack so the lower control arm will not move back by the spring pressure. I you let the lower control arm move back you run the risk of the spring popping out.
You will also likely need a come-a-long cable wench to pull the lower control arm forward to fit the guide rod back in place.
I jacked up the car on to stands, then used the floor jack to raise the lower control arm.
I then dropped the guide rod bearing sub-assembly and rotated if off the guide rod.
I next changed out the guide rod bearing from its assembly and then rotated it back on the guide rod.
The important thing to do with this procedure is to make sure the lower control arm is slightly lifted and stable by the floor jack so the lower control arm will not move back by the spring pressure. I you let the lower control arm move back you run the risk of the spring popping out.
You will also likely need a come-a-long cable wench to pull the lower control arm forward to fit the guide rod back in place.
Last edited by pwogaman; 10-01-2006 at 06:16 PM.
06-02-2016, 06:26 PM
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1990 W126 560SEL, 1995 W124 E420, 2000 W210 E320 wagon non 4 matic
great story and good communication. I have started this job, but did not realize the spring would move back, I used a come along but stopped. I have decided to remove spring and also replace control rod bushings as well. I failed to realize the spring movement or I would have been done and riding smoothly. Thanks for excellent story and I hope the dogs did not get sick! 
12-30-2018, 07:36 PM
#4
Junior Member
No need to pull the springs. Also, a large hose clamp tightened around the new bushing let's them almost fall into place. Make sure to position them in the bracket such that the drain slot is on the bottom.
I've done several. Very easy job.
I've done several. Very easy job.
05-14-2019, 08:02 AM
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420 SEL
Where to buy?
Does anyone have a reliable source to buy these Guide Rod Bushes - struggling to locate some!
05-14-2019, 08:32 AM
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1990 W126 560SEL, 1995 W124 E420, 2000 W210 E320 wagon non 4 matic
I used
I found the Meyle brand to be supieor in one important area the long top keeper that you bolt into frame with the Lemforder one broke while torquing into position had to reuse old one, this is the clip that has nut welded on it and slides into top of frame to bolt the dog leg into. I purchased both of mine on Ebay, but many others carry them as well, peach parts, mercedessource FP euro etc.
