.. ball joints that is.

Its too cold to work outdoors on the cars, so I decided to get destructive with the failed UCA I replaced on my 300D turbo and find out what things were like inside it, maybe even understand why it wore out. The failure I experienced was visible vertical play -- I could move it vertically about 3/16" (2mm) by hand and could see it moving more under higher load. Others might not call that worn enough to replace, but I do.

Pictures (1-4 of 8):
1: The control arm, showing the MB logo. This looks to be a genuine MB replacement part.

2: Ball joint sans boot. Everthing is bathed in what appears to be good grease. I wonder why it wore out?

3: Boot and glued-on retainer ring. It doesn't show from this picture, but the boot is in good condition -- no cracks or tears. I took the ring off for practice, but because it was glued in place with that yellow stuff, it was a bear to remove. I also bent it a bit getting it off, so I don't know how well it would seal if I had to put it back on. With a glued on ring, this is definately the original boot.

4: Cutaway. There's the ball, surrounded by a thin grey plastic socket liner and a yellow plastic cap on top. Notice in this picture how the grey liner extends all the way to the hole in the arm.

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'83 300DTurbo http://badges.fuelly.com/images/smallsig-us/318559.png

Broadband: more lies faster.

Pictures 4-8 of 8:

5: I was curious why these were nonreplaceable and here's my answer -- the UCA is formed up and over the top plate. We all knew this already, it was just an interesting photographic challenge to get a picture of the joint between the dissimilar metals.

6: The liner with the ball and cap removed. Now we can see how this joint failed -- the plastic liner wore out and the ball was bearing directly on the UCA metal. You can't see it from my picture, but the plastic liner is feathered towards the edge, but then cracked off where it gets too thin. There's a fair amount of metal to go in the UCA, so we're not talking imminent failure or anything.

7: And here's what caused the joint failure -- the ball itself -- after I got it out and cleaned all the grease off. Notice the pitting and rust. The end that goes into the knuckle shows some machining, but the rest is this nasty, unmachined, rusted part. That roughness and rust grit is probably what ground away the plastic liner.

8: And finally, here's the entire ball piece itself, along with a few other pieces. I've included this picture to show that the most exposed part of the joint, the threads, are not rusty.

Sorry about some of the blurry pictures, I didn't want to take the expensive camera down in the shop.


I don't think this joint rusted after assembly since only the non-machined part shows any hint at all of rust. Which leaves me with a few questions:
* Is this sort of construction with a rough, rusty casting for the force-bearing part common?
* And, has anybody else opened up their old ball joints to see what kind of wear was inside and what caused it?

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'83 300DTurbo http://badges.fuelly.com/images/smallsig-us/318559.png

Broadband: more lies faster.

Very good pics and nice dissection of the ball joint. Looks like you had some fun slicing into that thing

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-justin

1987 300TD, 1987 300TD
2008 R32, 2000 Passat Wagon

Thats cool, didn't know there was a plastic shim inside.

Was the ball worn in the cup? Thats where it seemed mine were worn.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

No breach in the boot prior to removal?

Weather sucks here too. Getting cabin fever. Gonna fire up the soldering iron and tear open an old Crown DC300A.

I haven't quite figured terminology out yet. The grey plastic "liner" is probably the cup your referring to. Yes, it was worn completely though to the metal, but only in two spots, and only on the bottom of the cup. I destroyed one of the wear spots getting into it, but pic 6 shows the other. Aside from this wear, the grease groves in the cup were also in good condition everywhere except close to the two wear spots. The yellow plastic cap looked in good condition too --the grease groves were of uniform depth throughout.


But you're asking about the ball itself, right? No, no signs of wear on it. It has the same uniform texture and color (and rust pits) all the way down to the machined section. The only shiney spots anywhere on it are consistent with my sawing the joint open.

Quote:

Originally Posted by Whiskeydan No breach in the boot prior to removal?

No. And none after. I didn't damage it taking it off the car, and I undid the ring to remove it from the joint. It is still flexible with no tears or cracks (and full of grease). I didn't install this UCA, so I suppose it is possible the boot was replaced, but I don't think so. The ring deformed enough that it would never realign like it was before I removed it, and it was glued together and to the rubber of the boot. Is it standard practice to glue the ring down when replacing the boot?

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'83 300DTurbo http://badges.fuelly.com/images/smallsig-us/318559.png

Broadband: more lies faster.

i don't know about the glue. afaik they don't glue replacements.

also replacement boots are available from your favorite benz parts guy.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I really enjoyed looking at the pictures. I am very surprised at the corrosion on the ball. I certainly would not have expected that with the grease and rubber boot intact. I am surprised. thanks for the nice pictures.

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Junqueyardjim
Christianity, if false, is of no importance, and if true, of infinite importance. The only thing it cannot be is moderately important. C.S. Lewis



1983 Mercedes W123 240D 4 Speed 285,000 on the road with a 617 turbo, beautiful butter yellow, license plate # 83 240D INDIANA

2003 Jaguar Type X, AWD. beautiful, good mileage,
Mom's car, but I won't let her drive it!

for new members

Grease dried out with age? Grease bleeds out a supply of thinner oils. As this deplets the grease dries and thickens.

It sounds like lubrication was lost enabling the rust. Pain in the ass but perhaps these lifetime joints need relubed somehow over the decades.

Zerk fitting would be a nice ideal if possible. Hitting them once every couple of years.

Injecting a little oil with a syringe through the wall of the joint boot and putting a tab of something over the miniscule hole might rejuvinate the old grease a little. At least the oil would inhibit aditional rusting if there.

I lifted the edge of the boot just enough to put some very heavy(680 wt)oil in mine.

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1977 240D turbo

I agree that the corrosion was the cause of the failure. Wonder if the boot had been replaced.

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1982 300SD " Wotan" ..On the road as of Jan 8, 2007 with Historic Tags

I have recently injected grease, using a grease injection needle, into the boots of the upper ball joints of my '97 E 300 D, to quiet some significant squeaking of the ball joints. I put a few pumps of grease into the loudest one, and had about one pump come back out of the hole I punched, probably due to the inflation of the boot and the compressed air. The puzzle was that after setting overnight, there was no squeak, but after a day of around town use the squeak was back, but at a reduced volume. This pattern repeated until after about four days the squeak was gone. I decided to try to eliminate the air in the second one so I could fill it up completely. I punched a hole near the top of the boot and then injected grease in a different spot until grease came out of the air hole. It still took a couple days to get it completely squeak free.

I had thought that the working of the suspension would "splash" grease from the boot up onto the ball. If it happened at all, it took a long time to happen. In hind sight I probably should have done a bit of interstate driving right after I had injected the grease to get a more violent suspension movement. It will be interesting to see how long this lube job will last. The ball joints show no play, so I am hoping for a much longer life for these joints. I believe I will do the lowers as well.

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'97 E 300 D

Try not to run them till they look like this.

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Jim

In my opinion the old dried out grease was a barrier to fresh lubricant reaching the wear or contacting surfaces. That is why I like adding oil in a situation like yours.

Otherwise the oil component leaving the new grease slowly takes it's time softening up the old grease and allowing some of the oil component through to the surfaces. With a zerk fitting the new grease displaces the old enough to provide the lubricant to the surface much quicker if not instantly.

The other factor is the oil can be inserted using a small needle leaving a much smaller hole in the joints boot. Remember the original grease is stil in there in most cases and has just dried out and needs rejuvenation.

To understand the process drop a dab of grease on a piece of paper and leave it. You should see an increasing ring of leakage from the grease expanding with time outward as long as the grease can supply the oil. At some point the grease will have dried out and the ring will stop expanding.

This to me is the way grease really lubricates. We can buy all kinds of high pressure grease etc. Common sense is that with enough pressure it is squeezed out and will not flow back in with very high viscosity. Viscosity increases with the leakage of oil from the grease as well. So the oil component intrinsic to the grease bleeding out does the real job usually. Of course there will be spins on what I think.

I still feel like I might be viewed as a junkie when aquiring syringes and needles at the local drug stores. Especially by personel not knowing me well.