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  #1  
Old 01-14-2005, 08:33 AM
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Front suspension rattle 300SD

I've searched for a half hour and can't find what I thought would be a common problem.

The left front suspension rattles going over small road irregularities. Also, after stopping, especially hard, and then releasing the brake, the suspension "gives" a bit and clunks.

I'm not well-versed (yet) on suspensions in general, so I need a bit of guidance on how to check for what is loose/worn. This weekend, I'll crawl under the car (on the cold hard gravel) and start pulling on stuff. Where should I start?

Thanks in advance.
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1984 300Sd 210k

Former cars:
1984 300D 445k (!!) (Strider) Original (and not rebuilt) engine and transmission. Currently running on V80 ( 80% vegetable oil, 20% petroleum products). Actually not, taking a WVO break.
1993 300d 2.5 275k. Current 120/day commuter
1981 300SD 188k (Hans) Killed by a deer
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  #2  
Old 01-14-2005, 08:53 AM
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lower ball joints
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  #3  
Old 01-14-2005, 09:07 AM
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If it only does it when it is cold I would say lower control arm bushings - but check lower ball joints as well.
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  #4  
Old 01-14-2005, 09:45 AM
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If you are getting noise while braking, you need to check the guide rod bushings (also known as strut rod bushings). The guide rod holds the front wheel/hub assembly from moving fore and aft while braking. If they weren't there, the wheel/hub assembly would roll under the car during braking.

The welded bracket that holds the guide rod bushings to the frame of the car can crack. When that happens you need to have the bracket welded back together, its not really replacable.

If you are getting that much noise, you ought to have the entire suspension checked out properly. Generally more than one component has wear.
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  #5  
Old 01-14-2005, 10:01 AM
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Hey,
I have a similar problem. I get a kind of thumping noise when I hit a bump but only with the wheel turned. And mostly on the right side. It doesn't do it at all when Ihit a bump with the wheels straight.

I'm suspecting ball joints but I'll check bushings and for other problems at the same time. As I understand it you check ball joints by jacking up the car and supporting the wheel at the A-frame and rocking the wheel from top to bottom. If there is any play it's the ball joints.
Is this right or is there a betterway?

Also I've read in posts here that the ball joints on these cars can be a royal pain in the ass. Any comments?

I'm going to Wyoming for the week so it will have to wait till I get back.

Danny
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  #6  
Old 01-14-2005, 11:24 AM
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Strut rod/trac rod bushings. Difficult DIY project for the mere fact that you must compress spring (special tool required) and if it gets away from you will go through anything in its path, including human tissue.
I have also found the only way to diagnose the front end of the SD is to put it up on racks and take a very large pliers and "test the joints for play by compressing them, also using a crow bar in specific point to see if there is excessive play in the trac rod bushings and upper ball joints.
I rebuilt the whole front end on mine, put on some bilstiens and now runs like new. I still have a little steering play but that is from the box. If you have 100K or more on the car the whole suspension should be expertly checked. Once brought up to snuf you will be amazed at the difference in ride.
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  #7  
Old 01-14-2005, 12:32 PM
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Maybe this will help you isolate:

I have been through my suspension, literally one piece at a time. Not the best way to do it but, as a result, discovered some of the differences in the "noises".

Worn ball joints usually give a shifting feeling when going over bumps. Irregular tire wear is common.

Worn guide rod mounts usually make a clunking noise during braking and going over bumps in the road. You "feel" it mostly under your feet.

Worn idler arm bushings and tie rod ends are usually felt in steering play.

Worn control arm bushings are usually felt under hard braking. A "give then click" feeling.

There are others but these are the major ones.

Suspension components can be a little hard to track down sometimes because of spring tension and geometric positions of the components in different situations. Pry bars, jacks, large pliers, etc... and weight on/off.
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  #8  
Old 01-14-2005, 02:12 PM
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Why would it not be the upper control arms (with upper ball joint) and the sway bar bushing that it attaches to? My 1984 300SD is doing the same as yours and looking at it while my wife drives in the driveway, I can see the upper control arm bushing moving back and forth and banging against the sway bar when braking. Also the protective boots are torn on the upper ball joints. Did not see or hear anything from the guide rod/subframe bushing area.

I had a lower ball joint go bad in my W126 and you could feel the steering wheel shake while driving around curves, plus bad tire wear. It did not make any noise when braking or bumps, lower ball joints you will feel and hear (W124s) more when the steering wheel is turned.

I suspect it is the upper control arms/ball joints/sway bar bushings.
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  #9  
Old 01-14-2005, 09:26 PM
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Thanks for the advice - I'm going under tomorrow. I hate working on cars when it's below freezing...
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1984 300Sd 210k

Former cars:
1984 300D 445k (!!) (Strider) Original (and not rebuilt) engine and transmission. Currently running on V80 ( 80% vegetable oil, 20% petroleum products). Actually not, taking a WVO break.
1993 300d 2.5 275k. Current 120/day commuter
1981 300SD 188k (Hans) Killed by a deer
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  #10  
Old 01-15-2005, 12:21 AM
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Based on my SDs

I can almost guarantee that it is the guide rod mounts or I think the manual calls them brake support rods. They run from the wheel back to the chassis and the mounts are easily visible from the outside of the car. by looking behind the front wheels at the rod that attaches to the undeside of the chassis.

I did the job on my car in about 3 hours with no help. It is really straightforward and even on mommie's 84 that has been kept in good shape it eliminated all the noises that were coming from the front end. On the 81 there was virtually no rubber left on the chassis mounts and I could actually see the front wheel move backward a few inches when I rolled ahead slowly and then hit the brakes hard. Pretty scary to see when you realize you just came off the highway running at 65.

I don't remember which kit I got from fastlane but I think the lemforder kit and it had absolutely all the parts including the new "loktite" impregnated bolts for remounting the cross frame member.
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  #11  
Old 01-15-2005, 12:31 AM
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Quote:
Originally Posted by SD Blue
I have been through my suspension, literally one piece at a time. Not the best way to do it but, as a result, discovered some of the differences in the "noises".

Worn ball joints usually give a shifting feeling when going over bumps. Irregular tire wear is common.

Worn guide rod mounts usually make a clunking noise during braking and going over bumps in the road. You "feel" it mostly under your feet.

Worn idler arm bushings and tie rod ends are usually felt in steering play.

Worn control arm bushings are usually felt under hard braking. A "give then click" feeling.

There are others but these are the major ones.

Suspension components can be a little hard to track down sometimes because of spring tension and geometric positions of the components in different situations. Pry bars, jacks, large pliers, etc... and weight on/off.
That is a good list.

I wish to add a noise that is best characterized by a "thunk" coming from either the LF or RF. The "thunk" is evident on decent sized bumps, but requires the steering to be turning the vehicle at the same time. It is somewhat random. You may drive for awhile and never hear it, but, if you stress the front end and hit a bump, you hear the "thunk" immediately. You may think it is the shock, because nothing else makes any sense, but it is not.

The bushing that secures the swaybar to the body has disappeared and the sway bar is left to "thunk" on the body when the suspension is loaded and the vehicle hits a bump. A bad bushing on the opposite end of the swaybar, in the upper control arm, is adding to the issue.

The vehicle pulls rather dramatically on heavy braking toward the side with the bad bushing, because their is nothing securing the upper control arm and preventing it from moving rearward when the brakes are applied.
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  #12  
Old 01-15-2005, 12:35 AM
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My vote is with the guide rod mount/caster ball joints. I went through the whole front end and one of the symtoms you are having was eliminated by replacing the guide rod mount. Fast lane sell a kit for around $80, I did not have to compress the spring out either. Once you go under the car, hopefully it will be very clear to notice since in most cases the boot is torn and rusted ball joints with dried up grease are very visable.
The second sound you are explaining the "thunk" is usually front sway bar bushings as Brian has explained in above post.
Good luck and keep us posted
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  #13  
Old 01-15-2005, 12:45 AM
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Quote:
Originally Posted by meltedpanda
Strut rod/trac rod bushings. Difficult DIY project for the mere fact that you must compress spring (special tool required) and if it gets away from you will go through anything in its path, including human tissue.
I have also found the only way to diagnose the front end of the SD is to put it up on racks and take a very large pliers and "test the joints for play by compressing them, also using a crow bar in specific point to see if there is excessive play in the trac rod bushings and upper ball joints.
I rebuilt the whole front end on mine, put on some bilstiens and now runs like new. I still have a little steering play but that is from the box. If you have 100K or more on the car the whole suspension should be expertly checked. Once brought up to snuf you will be amazed at the difference in ride.
if your talking about guide rod mounts you are wrong,the oly thing that would require removing the spring is the lower control arm. i have had everything possible apart on my sd exept the dash,crancase,and the tranny. i have even done guide rod mounts on it and i will be soon on my new sd.
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  #14  
Old 01-16-2005, 02:53 PM
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Thanks for all the guidance. I checked underneath today (with stiff cold fingers) and didn't see anything obvious. But after reading all I could on the subject, I'm nearly sure it's guide rod mount.

For those who have done it, a few questions.

Where is the best place to support the car? The large bracket that crosses underneath? I have jack stands but I want to know the best place to put them so they're not in the way.

I'm not real clear on how to get out the large rubber mount. Does the entire bracket have to be removed, or is the mount removeable without doing that? There seems to be some bolts that will be hard to get to without removing the bracket. Someone mentioned having the bracket out and pounding out the mount. Is that the best way?

Is there anything else that I'll already be halfway to that I should go ahead and do (assuming a short, cold weekend in which to do them)? Nothing else looks bad or loose and the car handles fine with the exception of the clunking guide rod.

Thanks for all your help!
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1984 300Sd 210k

Former cars:
1984 300D 445k (!!) (Strider) Original (and not rebuilt) engine and transmission. Currently running on V80 ( 80% vegetable oil, 20% petroleum products). Actually not, taking a WVO break.
1993 300d 2.5 275k. Current 120/day commuter
1981 300SD 188k (Hans) Killed by a deer
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  #15  
Old 01-16-2005, 03:53 PM
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Yep ... It's the Ball Joints

I had the exact symptoms as you with my '86 SDL. I felt the clunking when I braked and when I went over bumps. It turns out to have been the ball joints, and for good measure, I also had the idler arm repaired (see the kit on FastLane). However, I had my mechanic do it, as I didn't know about this group at the time (doh!) However, it was worth the $$ since my ride has been very tight, and I've even experienced improvement in the steering. Plus, no more klunking.

I have other parts of my front end to rebuild, including the upper control arm. As a result, I've researched how to do that, and learned about the ball joints as well. Since the front end is all interconnected, it would make sense to replace other items as well. The parts are modestly priced - it's the labor involved in changing them that costs $$. This is an easy thing to fix, as long as you're comfortable with wrenching.

Just a suggestion that I've seen mentioned time and time again, and I also saw on this post. Don't do anything with the springs without using the proper compressor. These springs are very heavy duty and the strength when they are compress is amazing! I've seen pictures where people have used regular compressors and (ulp!) compressors for McPherson struts! Seeing steel bend is unnerving. I sure as heck don't want to find out what the tensile strength of the steel for the non-MB compressors is. If you're going that route, rent or buy the proper compressor. Better yet, leave that to your trusted Indy.

For what you are doing, though, you don't need to change out springs. Be sure to research changing out ball joints thoroughly on the forum, as others have safety and practical tips. Also, Thomas Pindelski, a frequent contributor, has a site with great pictorals about various maintenance items on the W126. He charges an annual subscription, but I am happy to give him something for the valuable information he has provided. Go to http://www.pindelski.com for more details.

I'd suggest changing out your upper control arms - if you have any squeeking or squishing noises when you go over a bump, that's it. On mine, the protective rubber boot is shot and it's time to act on them. Also, a good thing to change when changing out the ball joint is the ball joint carrier bearings (AKA "front subframe bushings"). Again, look on this forum for how to change them.

Hope this helps. And remember safety, safety, safety if you do any work on the front end.

Casey
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