Removing the Brakes - PeachParts Mercedes-Benz Forum

pawoSD · #1 10-26-2004, 06:00 PM

Ok we tried to get our brakes off our '83 and aren't able to losen the bolts on the calipers, what should we do to get this stuff off? Is there a specific tool or method to being able to work on the brakes on this car? Please help.

Essentially what is the step by step process (with which tools ect...) for changing the brake rotors and pads........are there any hints that could help in this?

rdanz · #2 10-26-2004, 06:56 PM

First buy yourself a repair manual like Haynes and read,read,read.
The rest comes easy.
Good luck

Brian Carlton · #3 10-26-2004, 06:59 PM

The calipers are held on by two cap screws that are torqued to 80 ft.lbs. It takes every bit of strength that I have on a 15 inch breaker bar to break these loose. Just be sure that the socket sits squarely on the flats of the cap screw and don't let it get cocked when you are applying the muscle.

Once the caliper is off, you can easily remove the rotor and hub from the spindle. Then you get the fun of trying to break loose the cap screws that hold the rotor to the hub. These use a 10 mm. allen wrench IIRC, however, you will never get them out with an allen wrench. Go over to Sears or Home Depot and get a set of hex bits to fit your socket wrench. Make sure that you have a 1/2 inch breaker bar and get the adaptor to fit the 3/8 hex bit onto the 1/2 inch breaker bar. They are very tight and it takes quite a bit of muscle to get them off. BTW, you need a good vice to hold the rotor, or, you can install two lug nuts and put a decent bar between them to provide the counter torque.

This will get you started.

tangofox007 · #4 10-26-2004, 07:16 PM

Make sure you are trying to loosen the bolts that attach the caliper to the steering knuckle and not the ones that hold the caliper halves together. It is easy to get them mixed up. And you don't want to separate the caliper!!

pawoSD · #5 10-26-2004, 08:08 PM

Thanks! I will do that, I did do one thing successfully tonight, replaced my door check on the rear driver side door, the original was in horrid shape

One of the ball bearings was rolling around, and the two bolts on the side of the door (where it comes out of the door itself) were actually broken off the mechanism, and the third bolt on the back of the check was real loose. The new one glides like butter, its an amazing difference. One by one I make the repairs....I will look into getting that manual....

Brian Carlton · #6 10-27-2004, 09:31 AM

Haynes does not make a manual for the W126, however, this manual, for the 123 should be part of the library for every person on this forum. Many of the techniques listed for the W123 are applicable to the W126. I still refer to it periodically.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=6762&item=7930540896&rd=1

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=34227&item=7930787070&rd=1

pawoSD · #7 10-27-2004, 07:10 PM

Do we have to do anything to the bearings if we just want to replace the rotors and pads right now? We don't have the tools or grease/seals for doing bearings, is it possible just to do the rotors/pads??? Bearings don't look fun!

tjohn · #8 10-27-2004, 07:44 PM

There's a pictorial right here under the DIY tab. Since you don't have antilock brakes, it's actually even easier.

Brian Carlton · #9 10-27-2004, 07:56 PM

Quote:

Originally Posted by pawoSD

Do we have to do anything to the bearings if we just want to replace the rotors and pads right now? We don't have the tools or grease/seals for doing bearings, is it possible just to do the rotors/pads??? Bearings don't look fun!

Bearings are not a big deal and, yes, you have to do the bearings. They need to be "repacked" with fresh grease every 30K or so and it would be foolish to put new rotors on without doing the bearings.

The outer bearing comes right out. Put it in a can of paint thinner.

You need to pop the grease seal out of the inside of the hub to remove the inner bearing. The grease seal is old and will be destroyed when you pull it out. Be careful not to shove a screwdriver into the seal and damage the bearing right behind it. When you get the bearing out, put it in the same can of paint thinner.

You need to buy new seals from Fastlane or from the dealer.

Shake the can of paint thinner for 15 minutes or so to get all the old grease dissolved. Remove the bearings and allow them to dry.

You also need to get a tube of wheel bearing grease. Each bearing takes about 50 grams of grease. You try and force as much grease as possible into the rollers. It takes about 10 minutes per bearing to do it right. Add some additional grease to the raceway (after you have thoroughly cleaned it out, of course) and place the fully greased inner bearing into the raceway.

Now you must reinstall the new seal. This is a bit tricky because the seal is larger than the opening and you cannot smash the edge of the seal with a hammer or you will destroy it. Get a suitable socket that is large enough to sit on the seal and hit that. The seal will start on down and you can seat it.

Pack the outer bearing with grease and put some grease onto the raceway and place the outer bearing into the raceway.

Now you are home free and can reinstall the rotor onto the spindle. Be careful that the spindle does not push the outer bearing right out of the hub. The end play should be very low, not more than .001. This is very difficult to achieve without a guage. However, you are looking to remove just about every bit of play, without causing any pinch on the bearings.

Good luck.

tangofox007 · #10 10-27-2004, 08:11 PM

Don't reinstall the bearings until you have the new rotor bolted on. And make sure you don't mix the left and right wheel bearings. The bearings need to go back in the same hub that they came out of. In my experience, most auto parts stores carry the wheel seals. You also might want to pick up a can of brake cleaner. It is good for cleaning the solvent out of the bearings prior to greasing them. Any residual solvent will affect the grease in a negative way.

psfred · #11 10-27-2004, 08:32 PM

You really should repack the bearings when you replace the rotors, it's impossible to change the rotors without getting grit in the wheel bearing grease.

This is easier than it sounds -- I'd get a new seal (wheel seal, under driveline on FastLane), you don't need to remove the races or replace the bearings unless they are bad.

To do the rotor and pads:

Drive pins out and remove pins and spring. Pry back on the pads to get clearance to remove them and pull then out. Often fairly stuck, have patience!

Remove caliper. Hang somewhere with some wire, don't leave it haning on the hose, it can tear and give you no brakes later.

Use a large pair of vise grips to pull the spindle cover off. Do not hammer on the sides, use the pliers (more on this later).

Loosen the clamp screw (6mm allen, I think) and unscrew the clamp nut. You may have an antistatic ground clip in the spindle. If you do, carefully pull it out and keep it safe. Note the amount of grease in the cap.

Pull hub and rotor off the car, catching the outer wheel bearing and thrust washer as they pop out. Inner bearing may be tight, you may have to pull pretty hard. Worst case it will be stuck on the spindle, but usually stays in the hub.

Turn hub over and pry the seal out, then remove inner bearing. Keep the bearings save somewhere, wipe all the grease out of the hub, put hub in vise, and remove old rotor (five 10 mm allen head screws). Will be tight, but will cmoe out with a breaker bar.

Clean surface of hub where rotor sits and put a very thin layer of antiseize (aka MB brake pad past) on the contact surface. Just a tiny amount, it's just there to keep the rotor from rusting to the hub. Hub must be completely clean otherwise.

Clean the cosmoline off the new rotor with brake parts cleaner. Wipe dry, then take some rough sandpaper and sand both sides to rough them up and obscure the machining marks.

Bolt new rotor to hub, tighten bolts to 60-80 ft/lbs. Probably best to use a timy amount of blue (removable) Locktite on the threads -- just a tiny spot will do.

Wash bearings in gasoline or brake parts cleaner to remove all the old grease. If the rollers are gray, have lines on them, or chips, etc, renew bearings and races. Unless you dropped them on the floor, though, they should be fine.

Using a knife, fill the central cavity of the hub with new synthetic wheel bearing grease level with the inside of the bearing races. Center should be free of grease (where the spindle goes).

Fill the inner bearing with grease by wiping it in with the knife. Drop into the back of the hub, then gently tap the new seal in. Best to use a socket or other driver that is a similar diameter. Watch that you keep it dust free -- if you get grit in it, you will have to clean and repack the bearing.

Wipe off spindle and remount hub and rotor. You will need to press fairly hard to get the new seal over the sealing surface on the spindle.

Insert outer bearing and washer, then screw on nut and tighten while turning the hub and rotor until it becomes significantly more difficult to turn (this presses the grease out from between the rollers and races), then back off 1/3 turn. You should be able to push the thrust washer from side to side. If no, back of a bit more until you can. It can be stiff, but must move with gentle pressure.

Pull out and push back on the rotor. If you can feel it move, retighten and then back off again, it's too loose.

If you have a dial idicator, the proper clearance is 0.001 to 0.002 inches, no more.

Tighten clamp nut to 20 ft/lbs.

Remove old grease from cap, put the same amount of new synthetic grease in, then press cap onto hub. Using a drift or punch, tap around the rim at the base ONLY to drive it home. Keep grease off the edge of the cap, it can seal so tight the cap will pop off from the trapped air!

Never use a hammer on the sides or top of the cap, it will dent the cap and cause the mouth to warp inwards -- the cap will then keep falling off.

Clean rotor to remove all the greasy fingerprints you got on it.

Re-install caliper.

Push pistons back with a C clamp or pliers. Do not pinch the dust boot, cuts in it will cause stuck pistons rather quickly.

Clean all the dust and corrosion off the slots where the pads sit. Must be nicely clean, no dust or rust.

Coat the sides of the backing plate (not the friction material) with antiseize. Put a ring of anteseize on the back of the pad where the piston touches, and install pad in slot.

Repeat for the other pad.

Put a spot of antizseize on the anti-rattle spring where it touches the backing plast on the pads. Put some where the pins sit, too.

Install spring and pins.

Remember to pump the brake pedal repeatedly until firm before moving the car, or you won't have brakes!!!

Other notes: if the bearings are shot, don't re-install, get new ones with a new race for each side. Races can be driven out with a punch from the opposite side, then driven back in with a punch. Keep the old ones separate from teh new ones, I've installed a bad one twice once when I was tired. Make sure they go in right side up, they are a devil to remove if put in backwards. Drive them down until firm hammer blows ring -- dull tapping means they are not seated yet. Make SURE the hub is spotless before starting! Timken bearings for any Benz are available ant any McParts -- they are all standard. Timkens fit TIGHT, but work fine.

If the pistons don't move back smoothly, make sure you remembered to remove the master cylinder cap, it only has a very small hole in it and the pistons won't move with it on. If still stiff, the pistons are stuck and you need to rebuild the caliper (actually just clean it up and replace the seal and dust boot with heat shield -- another post!). You can free them up sometimes by clamping the other one down and stepping on the brake pedal, but they won't work properly since the seal is bad and there is dirt in the upper caliper bore.

Peter

phantoms · #12 10-27-2004, 10:03 PM

Quote:

Originally Posted by Brian Carlton

Haynes does not make a manual for the W126, however, this manual, for the 123 should be part of the library for every person on this forum. Many of the techniques listed for the W123 are applicable to the W126. I still refer to it periodically.

http://skinnerbox.steaky.org/Service/W126/Main.html

Brian Carlton · #13 10-27-2004, 10:14 PM

Quote:

Originally Posted by phantoms

http://skinnerbox.steaky.org/Service/W126/Main.html

Has anyone been able to get anything whatsoever from that site? Every page that I have attempted to load gives "The page cannot be found".

phantoms · #14 10-27-2004, 10:41 PM

Sometimes it's extremely slow and I think he's still working on the 126 part of the site. I had thought by now the pages would have been finished, but I guess I was wrong. I usually use it for the 123 pages (http://skinnerbox.steaky.org/Service/W123/Main.html).

jim16671836 · #15 10-27-2004, 11:45 PM

The brake parts and assembley/disassembley are the same on all the 123 Turbo, 116 and the 126 until maybe 1985. Same parts fit all 3 models...So the 123 book is a good one to have for doing the brakes on a 83-300SD. Jim