Please help before I kill myself - PeachParts Mercedes-Benz Forum

Carpenterman · #1 12-05-2011, 07:32 PM

After replacing the pinion seal, I am now on to the torque arm rubbers. The FSM doesn't have a procedure for this although it does have one for removal of the springs.

My question is this: can I use a jack under the front of the arm and just lower it after removing the fasteners where it attaches to the body? Will the spring just fall out? I have two "old-school" spring compressors, but couldn't get them positioned on the spring correctly due to inadequate clearances. I am concerned about safety, 'cause I've read stories about springs flying around the shop killing cats and stuff.

Also, should I get the axles more or less level before snugging-up the bushings? As you know, the axles travel in an arc and really distort the rubbers when they are at their shock-determined limit.

JimFreeh · #2 12-05-2011, 08:12 PM

I've read this twice, and am not certain what you are trying to do.

If you are talking about the semi trailing arms, place a jack under the rear of the arm, disconnect the shock, and raise the car/lower the trailing arm and the spring will fall out.

All rubber suspension bushings should always be installed loosely, then tightened only once the car is sitting at road height, all four wheels on the ground. You can accomplish this by driving the car up onto a set of ramps for access to the fasteners.

Jim

wbain5280 · #3 12-05-2011, 08:27 PM

He's referring to his Fintail trailing arms.

The manual shows spring compressors being used to compress the springs and remove them. Find ones with longer grippers to do this important function.

As far as the bushings are concerned, be careful which way the front bushings are installed, they only go in one way and they have the markings, in German. I'll scan the M-100 site for proper alignment. The axle mounts aren't that difficult.

Check the axle cuff for tears. The replacements are either split or not.

The swing axle joint may be bad, distorted, and need to be replaced. There are many small parts, so be careful.

The upper cross mount rubbers should also be replaced. There is also a small rubber bushing at the rear axle mount.

Check the EPC for the proper part numbers.

Get the repair CD which includes the Ponton 180/190 procedures. The Fintail procedures build on the Ponton book.

Carpenterman · #4 12-05-2011, 09:29 PM

Sorry I wasn't clear. The manual refers to these arms as "torque" arms, although on my w123 they are called "trailing" arms.

The front bushing has a marking for up (oefh or something like that). The cuff on my axle is fine. I am not prepared to tear into the axle joint, although I can see some of the rubber grease seals are getting soft and one of the zerk fittings is broke off. I'm going to replace that.

I will be replacing the cross mount rubbers next and once I get everything tightened and settled, I will align the rear end using a jig that I made. The axle mount bushing was replaced by the PO not too long ago. I was going to replace it anyway but the Classic Center wants insane money for it.

I have the paper parts book that covers everything but the engine (I don't have enough memory to use the EPC). I only have Volume 3 of the CD ROM manual which covers the 110s, the 108s, and the 109s. I'll look into getting the Ponton CD.

I'm not sure it is a good idea to disconnect the shock, as the manual says that the axle could overtravel and cause damage. I'll just be careful and lower the arm to get the spring out.

Thanks for the advice.

wbain5280 · #5 12-05-2011, 10:09 PM

Quote:

Originally Posted by Carpenterman

I have the paper parts book that covers everything but the engine (I don't have enough memory to use the EPC). I only have Volume 3 of the CD ROM manual which covers the 110s, the 108s, and the 109s. I'll look into getting the Ponton CD.

The EPC is free, they want your CC number. I suggest getting a visa gift card at the grocery store.

Your welcome. You will need the CD for the Pontons and Fintails, CD number 2.

RANDY P · #6 12-06-2011, 10:52 AM

Without knowing firsthand what it's like under there if you are concerned about that spring flying, find a decent sized chain and padlock try to secure the coil to the suspension.

A flying coil will ruin your day and probably take out a limb in the process.

You can try lowering the arm and hope it decompresses enough, but if it doesn't you will need the right spring compressor to put it back all together anyhow- so, make one attempt if it doesn't work bite the bullet and buy the compressor.

rjp

Stretch · #7 12-06-2011, 10:59 AM

How much longer are fintail rear springs compared with W123 rear springs?

wbain5280 · #8 12-06-2011, 01:16 PM

Quote:

Originally Posted by RANDY P

Without knowing firsthand what it's like under there

Then please don't speculate, W111's and W123's are much different. Thanks

Carpenterman · #9 12-06-2011, 01:51 PM

OK, I left the shock on, removed the big bushing nut on the body bracket (22mm), ran a jack up to the trailing arm just back of the body bracket, removed the three bracket to body nuts, and the arm came down and destressed the spring without any drama.

Now I can't get the axle bracket screws off even after de-staking. They are tight! Monkey wrench and then a pipe wrench--no go. I don't want to ruin the screws so I'm off to find a 36mm socket or wrench.

I''m learning that suspension work requires BF tools.

wbain5280 · #10 12-06-2011, 05:07 PM

Use a 50 - 50 mix of ATF and Acetone to soak the axle bracket bolts. It may take a few tries for it to soak in. They are tight after 40 years.

Carpenterman · #11 12-06-2011, 07:12 PM

The 36mm socket I found and a 2 foot breaker with a pipe cheater did the trick. One side is done. It was a little tricky squeezing the axle bracket bushings together to get the snap ring on, but I used three of my woodworking clamps and was able to get it together.

mercmad6.3 · #12 12-07-2011, 04:29 AM

yep,they can be super tight. I have resorted to welding a 18" long piece of 2" x1/2" bar to the bolt and whacking it with a hammer.
Getting the front bush back in is a real trick. Fit the spring and rubber top piece (tape it to the spring) on the spring plate so the end of the spring fits properly .
Fit the rubber front bush into the arm and lube the inside with talcum powder OR cooking glycerin . The nipple it pushes onto should be cleaned up and polished a bit. It's damn hard to fit if the rubber is dry and the nipple rusted .
Then simply jack the arm back up again ,watch the rubber so it doesn't push out.
Also,the spring only goes in one way,there is a top and bottom.

Carpenterman · #13 12-07-2011, 10:12 AM

Should those axle bracket screws go back in super tight? If I really tighten them, the arm does not want to move by hand. Does the pivot pin turn inside the rubber bushings or does the arm turn around the rubber bushings? Since the screws are staked to the arm, I'm guessing the pin turns inside the bushings. Should I worry about the arm not moving by hand when the screws are tight, or is it meant to be so tight?

Yup, the front bushing was a little tricky. I found it easiest to fit the bushing to the arm, fit the bracket to the bushing, then put the jack right under the bracket at the bushing. I had to use a pry bar to align the bracket to the body connections and the bushing to the nipple as it went up.

mercmad6.3 · #14 12-07-2011, 03:59 PM

yes they should and the rubber should be felt to grab the arm making it stiff to move. In place they don't move all that far in normal driving.
I have the mercedes alignment tool which makes fitting the bushes a two minute job.

Carpenterman · #15 12-07-2011, 10:24 PM

O.K. Madman. Will do. I've got the car off the lift and the rears on ramps to let the new suspension rubber settle. Tomorrow I'll tighten everything up and align the axle.

I'm hoping I've now cured the vibration over 50mph that I had. The suspension rubber was bad, but not terrible. The U joints were good but the carrier bearing bushing was a little loose. The bearing looked good, but I replaced it anyway. I suspect the real culprit was the rear engine mount which was totally destroyed.

Is it necessary to loosen the nuts where the front trailing arm bracket mounts to the body when doing the alignment? I notice there are slots in the bracket where the studs/bolts mount.