What's in your balls? upper control arm joint cut open - PeachParts Mercedes-Benz Forum

patbob · #1 01-15-2007, 03:09 PM

.. 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.

patbob · #2 01-15-2007, 03:19 PM

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?

justinperkins · #3 01-15-2007, 03:36 PM

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

Hatterasguy · #4 01-15-2007, 03:41 PM

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.

patbob · #5 01-15-2007, 05:30 PM

Quote:

Originally Posted by Hatterasguy

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

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?

t walgamuth · #6 01-15-2007, 06:34 PM

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

Whiskeydan · #7 01-15-2007, 03:49 PM

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.

47dodge · #8 12-02-2011, 05:32 PM

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

MS Fowler · #9 12-02-2011, 05:36 PM

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

nelbur · #10 12-02-2011, 09:24 PM

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.

engatwork · #11 12-02-2011, 09:31 PM

Try not to run them till they look like this.

smitherz · #12 12-04-2011, 08:17 PM

Quote:

Originally Posted by engatwork

Try not to run them till they look like this.

I see your lca and raise you this one.

Yes, it had just a little play in it when I bought the car. All better now.

barry123400 · #13 12-03-2011, 12:37 AM

Quote:

Originally Posted by nelbur

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.

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.

nelbur · #14 12-03-2011, 01:44 PM

Quote:

Originally Posted by barry123400

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.

Sounds reasonable to me that oil from the grease was crawling up into the ball area. That would explain why it took so long to totally eliminate the squeak. I thought about adding gear oil, but I found the boot on this car to be apparently crimped in place when manufactured, so I could not pry the top out to pour oil in. I bought my grease injection needle from Auto Zone. The only problem you will run into is that the staff will never have heard of such an item, so you will have to find it yourself with the grease fittings, etc. I would guess that a genuine syringe would require a prescription from a doctor, but the odds are good that your doctor has a Mercedes, and would be sympathetic.

barry123400 · #15 12-03-2011, 07:10 PM

Quote:

Originally Posted by nelbur

Sounds reasonable to me that oil from the grease was crawling up into the ball area. That would explain why it took so long to totally eliminate the squeak. I thought about adding gear oil, but I found the boot on this car to be apparently crimped in place when manufactured, so I could not pry the top out to pour oil in. I bought my grease injection needle from Auto Zone. The only problem you will run into is that the staff will never have heard of such an item, so you will have to find it yourself with the grease fittings, etc. I would guess that a genuine syringe would require a prescription from a doctor, but the odds are good that your doctor has a Mercedes, and would be sympathetic.

Quite the contrary. Druggists have always sold or usually given me what I needed. You just have to be cautious around those sharp points.

I use them as well for fussy oiling or glueing applications on small items. My experience is that they are almost one use as what I fill them with seems to either seriously stick the rubber portion of the plunger or attack it.

Thats if left sitting unused for some period. For those applications I grind the sharp point off to blunt the end of the needle as well. If you flushed them out after each use they may last for many uses. Drug stores stock quite a few sizes as well.