UCA Seating Question - PeachParts Mercedes-Benz Forum

dwylie34 · #1 01-23-2013, 10:13 PM

Hi All

I've been trying to diagnose a knock/croaking noise I get from the driver's side front wheel well when turning right and/or going over moderate sized bumps.

After inspecting I noticed that the driver's side UCA is seated in the spindle about 5-9 centimeters higher than the passenger side, I tried tightening with an extension which only served to strip the nut (which has now been replaced).

Nevertheless, could this cause a knock/croaking noise? The pics show the difference between sides (although they are not my images).

dwylie34 · #2 01-24-2013, 11:10 AM

My apologies if I was not clear, the UCA is new, as soon as I put it on it began this noise. I did a lot of other suspension work too - lower ball joints, tie rods, brake pads, rotors, left guide rod mount, LCA bushing, shocks - and this is the only thing I can think of that doesn't look right. Also, these pics are not of my car, but illustrate the problem with the upper control arm not seating.

whunter · #3 01-24-2013, 01:35 PM

Quote:

Originally Posted by dwylie34

My apologies if I was not clear, the UCA is new, as soon as I put it on it began this noise. I did a lot of other suspension work too - lower ball joints, tie rods, brake pads, rotors, left guide rod mount, LCA bushing, shocks - and this is the only thing I can think of that doesn't look right. Also, these pics are not of my car, but illustrate the problem with the upper control arm not seating.

Looks like a wrong part.
They should be exact mirror images, your pictures show variations.

.

dwylie34 · #4 01-24-2013, 06:15 PM

whunter

I thought so too, "the part must be defective or wrong" so I returned it and got a new one. Same exact noise under the same exact situation, which would make me believe it is something else, but it appears to not be seating correctly which still baffles me.

whunter · #5 01-25-2013, 12:55 AM

Is it possible a previous owner replaced one of the steering knuckles?
Call me Friday to discuss possible diagnosis/solutions.

.

dwylie34 · #6 01-28-2013, 07:06 PM

whunter

Thanks for the input today on the phone, I am investigating the possibility that this older (1980) w123 had a newer (1981+) knuckle installed on it at some point.

ROLLGUY · #7 01-29-2013, 12:42 AM

Having just done 2 front end rebuilds, are the knuckles different in 1980 and older form 1981 and newer? The reason I ask, is that I rebuilt a spare set of knuckles (new ball joints installed), and LCA's (new bushings installed) from a 1985, and installed them on a 1980. I then took the parts from the 1980, rebuilt them with new parts (BJ's & LCA bush'gs), and put them in my 1982 240D. I have the spares from the '82 that I will rebuild and use them in the next front end job. The '80 seemed to align just fine, and drives like a new car (suspension wise). I still have to get the '82 aligned after I replace the 2 tie rods tomorrow (after the parts arrive from Pelican Parts). Is there a problem with mixing up the parts like that? I assumed all the 123 chassis parts were the same......Rich

Zacharias · #8 01-29-2013, 08:28 AM

Quote:

Originally Posted by ROLLGUY

Having just done 2 front end rebuilds, are the knuckles different in 1980 and older form 1981 and newer? .... Is there a problem with mixing up the parts like that? I assumed all the 123 chassis parts were the same......Rich

I had wondered about doing as well, swapping between my immobile '78 Coupe and my '85.

dwylie34 · #9 01-30-2013, 06:30 PM

Today I went to the local yard with one of the UCAs that I knew was not seating correctly on my wagon. I tested it on the following: 1978 116, 1985 123, 1979 123, and 1985 (?) 126.

The point of contact between the spindle and UCA ball joint ALL sat indentically (of course the lengths and exact configuration of the arm itself differed, but I wanted to see how that threaded section from the UCA sat when inserted in different spindles) the ball joint bolt has a tapered design at the top and can apparently be insterted approximately 5-10mm before directly contacting the actual ball of the ball joint - see the images above with the rubber bushing compressed between the two parts.

I'm baffled

dwylie34 · #10 02-01-2013, 01:08 AM

So I looked at my neighbor's 240d today and it looks like the UCA sits a little bit higher than that of the 300d. Just a bit of qualitative assessment, but maybe about 1cm from being totally compressed against the rubber boot around the UCA ball joint.