Torque Spec, W126, Guide Rod Joint Hsg Bolts - PeachParts Mercedes-Benz Forum

Richard Howard · #1 08-06-2012, 07:42 PM

I've finally started work replacing the guide joint bushings in the '82 300SD and will enjoy the absence of noises when going over bumps.

The driver's side housing is now clean, with the new joint bushing in place, and is ready to reinstall.

Does anyone have torque specs for the two bolts holding the "L" housing carrying the joint to the car body? The two captive nuts on the metal strips that pass through the slots at the top of the bolt towers obviously can't take much torque but there must be a value that provides safety and protects the nut supports.

Also is there a torque spec for the bolt that holds the front end of the guide rod to the lower control arm? The rubber concave washer will compress a bit so a torque value here seems reasonable.

Thanks for any time used and for any information on the above.

SD Blue · #2 08-07-2012, 10:23 AM

If you can't find a specific torque value, there are generic torque values for the fastener size:

(ft-lb) (Nm/m)
M-8 14-21 19-28
M-10 28-40 38-54
M-12 50-71 68-96
M-14 80-140 109-154

eatont9999 · #3 08-07-2012, 11:40 AM

The specs would be good to know. I am about to start my guide rod repair as well.

Richard, how difficult was replacing the bushings and such? I don't have a press or anything advanced like that. How long should I expect the job to take? Any tips or tricks not mentioned in other threads?

Richard Howard · #4 08-08-2012, 04:58 PM

I just finished installing the bushing bracket with the new joint on the passenger side of the 300SD and again all went well.

As mentioned in other posts on this topic, count the visible threads on the old joint's threaded stud before removing the guide rod from the joint, to be able to reestablish the caster angle as best possible when reassembling.

Thanks to our always helpful and very savvy tech. rep. Roy Hunter, I learned that the bushing bracket to body bolts take 80 N. M. torque, and the bolt/nut holding the front of the guide rod to the lower control arm takes 50 N.M.

Time for each side seemed to be about four to five hours but I spent much time thoroughly cleaning the bracket in water soluble liquid parts cleaner. I used the purple colored product but the green liquid should work well. A dish washing brush with plastic bristles and a handle about 6 inches long is useful. Use gloves, of course. I used a 5 gallon plastic diesel fuel container with the top cut off to clean the parts in, with about two gallons of the cleaner so the piece could be submerged to soak. Rinse with hot or warm water from a plant watering can. I prefer to thoroughly clean parts before repair and replacement.... it just makes the job a better one.

To clean the corrosion from the bore where the new joint will go, use a three inch coarse wire wheel on the shaft of a bench grinder. It will enter the bore and cleans the deposits well. Work carefully as the bracket is aluminum. Use a dust mask and maybe an electric fan blowing air across the work area near the grinder.

To clean the threads inside the guide rod, use one of those round wire brushes (1/2" diameter brush) intended to clean the inside of copper pipe fittings before flux application before soldering. First wash out the inside of the rod with spray brake cleaner, then clean the threads with the brush (turn it only counterclockwise - not "back and forth", to avoid bending the wires excessively). Then flush with more brake cleaner.

Look at another post of mine here in this forum for a tip on how to help get the new joint/bushing started into the bore. This suggestion uses several of those stainless steel "worm-drive" hose clamps, one of which is used to compress the two sides of the new joint/bushing to make its outside diameter smaller. Lube the bore, the new joint's threads, and the threads inside the guide rod with grease to help with assembly steps.

I found that at some time in the past before I bought this 82 300SD, someone had worked in this area and had replaced the guide rod bolt on the passenger side in from the top of the LCA. This made it impossible to remove the guide rod without compressing the spring - which I did not do. The driver's side of the car had the bolt inserted from below, allowing it and the guide rod to be removed easily.

To protect the aluminum bracket from road salt and water, you could do as I did and spray on a coat of clear alloy wheel paint before reattaching the bracket and new joint to the car body. Before painting clean the surfaces with brake cleaner spray to promote good adhesion.