When I make a sharp left turn into my driveway I get a clunck sound when my foot is on the brake. The sound is not there when I coast in with my foot off of the brake. I checked the wheel for play and couldn't feel any, took the wheel off and inspected the caliper, everything looked solid. I did notice that the rubber sleeve on the tie rod end has a big rip in it. The tie rod has 60,000 miles on it. The car handles fine on the highway, no egregious vibrating or darting. Any ideas? Thanks

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'81 300SD

The sound will be coming from the control rod mount.

There is a heavy bar that runs from the lower control arm. The control arm is where the lower ball joint mounts. That control rod runs back to the frame and provides support for the control arm. At the frame, there is a mount and it is designed to allow some movement. In yours, you may find the rubber boot is gone and you can see what looks like a small ball joint - that is what allows the movement.

The control rod mount back at the frame has worn out. You may not be able to shake it by hand, but that is what clunks when you have the brakes on and hit a bump.

There are probably some visual indications of decay on the boot. When that boot wears out then you start throwing road grime and salt into the little ball joint.

If you search here on "control rod" you will find the replacement procedure and tips.

Ken300D

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1982 300D at 351K miles
1984 300SD at 217K miles
1987 300D at 370K miles

Thanks Ken,

After reading a few of the posts on replacement, I'll probably borrow my neighbors spring compressor and take out the spring on that axle to make the job easier. How much time do I have before I need to get this job done? I probably won't get to it for a month or so.

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'81 300SD

I would recommend you NOT do anything with that spring. It has a lot of power - consider how much the front of the car weighs.

All you really need to do this replacement (other than ordinary tools) is a tree and a come-along. Maybe a wheel chock. You jack up the car and remove the wheel. Then as you unscrew the guide rod adjuster to release the guide rod, you pull the hub forward using the tree and the come-along. The hub/control arm will flex enough to release the guide rod from the mount.

Then you replace the mount, then reverse the process.

Taking out the spring doesn't help this process much.

Just my opinion having done this job. It also occurs to me that you might have a worn upper control arm, so that deserves a check too. But I think the control rod mount is a likely candidate.

Ken300D

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1982 300D at 351K miles
1984 300SD at 217K miles
1987 300D at 370K miles

Thanks Ken,

Actually I think it is the upper control arm. I jacked up the front of the car and with the left wheel off, turned the wheels back and forth and could see the upper control arm move up and down and make a knock sound. I'll replace it next week,easy job.
Thanks for the advice on the rod mount, I'll have to do that job eventually.

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'81 300SD

Bad rear Guide Rod mounts are classic for making a clunk sound. In your case it sounds like it may very well be something else. Lots of things can clunk up there.

A bad Guide Rod mount will clunk while going over small imperfections in the road at slow speeds, while hitting the brakes and you won't have rock solid steering (it will wander).

I inspected my mounts with the car on the ground (no jacks). Grab the tire and rock very hard forwards and backwards while watching the rear Guide Rod mount. If the mount is bad it, the rod will pull in and out of the mount.

Here is how I did mine with some help from the forum (if you ever get to it). Not too bad:

Guide Rod mount fun

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AJ

1985 300D (SOLD)

Good news. Replacing the upper control arm and tie rod took care of the clunk sound. Now I'm hearing a click when I spin the wheel. When the car is rolling I can occasionally hear a squeak, probably wheel bearings. Do I need a special tool to press in the new bearings? Is this a DIY type of job? Thanks

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'81 300SD

No special tools for the bearings. However I would suggest that you replace the races too. That you will need special tools for.
Good drifts or punches to remove the old ones. Metal to get started, brass to finish, so you don't ruin the hubs. And a good 3 or 5 lb sledge hammer.
You will also need a bearing race & seal driver set like this one:
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=95853

It's not as hard as it sounds, just don't be afraid to give the old races some really good whacks to get them started.

Danny

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1984 300SD Turbo Diesel 150,000 miles

OBK member #23

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