Any special tools needed for W126 rear brake job - PeachParts Mercedes-Benz Forum

triacon · #1 03-26-2014, 05:59 AM

I have a 1985 300sd. Got to replace parking brake parts as well as rotors, calipers and pads. hoses too... will I need any special tools? May need a new bearing on the passenger side rear as well...

toomany MBZ · #2 03-26-2014, 06:39 AM

The FSM shows a couple of special tools, but maybe a generic shoe tool will work.

As for the calipers etc, just normal hand tools.

Be sure and clean the threads of the caliper mounting bolts, then use blue lock-tite.

vstech · #3 03-26-2014, 07:01 AM

The parking brake CAN be done without the mb specific drum tools... But it's a snap with them... I'd search eBay for "Mercedes brake tool set" get the two tool set
Item Id: 380602399145

jay_bob · #4 03-26-2014, 07:14 AM

+1 this is one of those cases where the specific tool turns an exercise in futility to a simple job.

Zacharias · #5 03-26-2014, 12:58 PM

He mentioned he may need a rear bearing as well.

There is a DIY by dmorrison on this that explains what is required:
PeachPartsWiki: Replacing the Rear Wheel Bearings

It is for the w123 but it applies to the w126 as well.

jay_bob · #6 03-26-2014, 01:37 PM

Just went through this with vstech on my 124 wagon. I imagine the steps are similar on a 126. Some lessons learned:

Support the car with stands in several locations. Place a floor jack under the LCA to allow the spring to be unloaded.

While you still have the brakes intact, unstake the big nut on the end of the axle shaft and break torque. You will need the parking brake and possibly someone standing on the foot brake to hold back against the effort required to loosen this nut.

Then remove the caliper and rotor. Hang your rotor up with wire to avoid stress on the hose. Better yet change the hoses while you are there.

Then disassemble the parking brake, here is where those tools come in handy. Don't forget to detach the parking brake cable from the backing plate. Also when you remove the actuator mechanism don't lose the little pin that holds the lever to the end of the brake cable.

Now you can get the dust shield loose so you can get to the bolts on the ends of the links and the LCA bushing that hold the wheel carrier in place. Carefully unload the spring using the floor jack.

Now you have the wheel carrier assembly free to either take to your shop press or to the machine shop for bearing replacement.

When pressing be careful of the following (BTDT on all of these):
- You will need a healthy shop press (50 ton min.) 12 ton HF special is not going to cut it.
- You will need a high quality bearing separator.
- Do not distort the dust shield plate, or the parking brake will not go back together properly.
- Do not damage the two ears that the caliper attaches to, or the caliper will not be able to be reattached. Bending those ears is cause for scrapping the [edit: wheel carrier], this is due to metal fatigue and the misalignment of the caliper. This happened to us when using a cheap bearing separator.
- The wheel bearing is one time press-in only when reinstalling the hub. Removal of the hub will destroy the bearing. So make sure you have everything put back together in the proper orientation before pressing in the hub to the new bearing.
- Be sure when pressing that you are applying pressure and backup support to the races in such a way that no force is applied that would pass from one race to the other through the bearing = destroyed bearing.

While you have the car this far apart it makes perfect sense to change the LCA bushings in the bottom of the wheel carrier.

Of course then you will probably see the split ends of all the links and the rotten subframe bushings.

That is how it snowballed on my car. OK... W124 Rear bearings are a BEAR to replace

charmalu · #7 03-26-2014, 02:39 PM

This HF Brake Spring tool is a help.

Search results for: 'brake spring tool'

I had a flat blade Screwdriver I ground down to fit into the Lug Bolt hole to install the Brake Shoe Springs. Pushed it in to rotate the Spring to hook it.

Since my last Brake job, the dang thing vaporized.

looked every where for it.

Charlie

Stretch · #8 03-26-2014, 03:16 PM

Super duper straight from NASA cost a fortune Y2K compliant =>

Home Made Special Tools, This is where members can share how they made special tools

jay_bob · #9 03-26-2014, 05:35 PM

The petite cargo hook and modified screwdriver are close analogs to the official tools and will probably work fine for brake removal.

vstech · #10 03-26-2014, 07:49 PM

nope, the 126 is identical to the 123, and bears little resemblance to the 124's bearing arangement... aside from properly supporting the car, Jays instructions do not apply to the 126.
just read up on the DIY mentioned above, and realize the massive difficulties involved in changing the rear bearings on your car, then start shopping for a good trailing arm to swap in... unless you really really want to change that bearing, with the one use only tool, and the massive crush preload fun...

Quote:

Originally Posted by jay_bob

Just went through this with vstech on my 124 wagon. I imagine the steps are similar on a 126. Some lessons learned:

Support the car with stands in several locations. Place a floor jack under the LCA to allow the spring to be unloaded.

While you still have the brakes intact, unstake the big nut on the end of the axle shaft and break torque. You will need the parking brake and possibly someone standing on the foot brake to hold back against the effort required to loosen this nut.

Then remove the caliper and rotor. Hang your rotor up with wire to avoid stress on the hose. Better yet change the hoses while you are there.

Then disassemble the parking brake, here is where those tools come in handy. Don't forget to detach the parking brake cable from the backing plate. Also when you remove the actuator mechanism don't lose the little pin that holds the lever to the end of the brake cable.

Now you can get the dust shield loose so you can get to the bolts on the ends of the links and the LCA bushing that hold the wheel carrier in place. Carefully unload the spring using the floor jack.

Now you have the wheel carrier assembly free to either take to your shop press or to the machine shop for bearing replacement.

When pressing be careful of the following (BTDT on all of these):
- You will need a healthy shop press (50 ton min.) 12 ton HF special is not going to cut it.
- You will need a high quality bearing separator.
- Do not distort the dust shield plate, or the parking brake will not go back together properly.
- Do not damage the two ears that the caliper attaches to, or the caliper will not be able to be reattached. Bending those ears is cause for scrapping the [edit: wheel carrier], this is due to metal fatigue and the misalignment of the caliper. This happened to us when using a cheap bearing separator.
- The wheel bearing is one time press-in only when reinstalling the hub. Removal of the hub will destroy the bearing. So make sure you have everything put back together in the proper orientation before pressing in the hub to the new bearing.
- Be sure when pressing that you are applying pressure and backup support to the races in such a way that no force is applied that would pass from one race to the other through the bearing = destroyed bearing.

While you have the car this far apart it makes perfect sense to change the LCA bushings in the bottom of the wheel carrier.

Of course then you will probably see the split ends of all the links and the rotten subframe bushings.

That is how it snowballed on my car. OK... W124 Rear bearings are a BEAR to replace

jay_bob · #11 03-26-2014, 09:31 PM

Ok my bad

I thought about that after I posted, and suspected as much.

triacon · #12 03-29-2014, 09:40 PM

well I'm not even sure if my bearings are bad on the rear right. I think that perhaps the caliper is not working properly and I hear a lot of rubbing because it is not releasing.
for now I will replace the hoses , the calipers the rotors and pads and I am not going to deal with the parking brake. so it sounds like I will not need any special tools unless I have a problem with my parking brake and /or bearings... thanks for the advice!