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  #1  
Old 11-02-2008, 06:55 PM
79Mercy's Avatar
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How to guide to replace front Brake Pads and Rotors on a W123



I thought I would make this pictorial for all the people that are clueless as to how to do this job, just as I was at first. I hope this helps everyone.

You need:

2 front rotors
Set of front pads
Disc brake wheel bearing grease
Brake pad paste
10mm hex socket
5mm hex socket
19mm socket
Torque wrench
Channel locks
DOT 4 brake fluid

  • Jack up the car and place on good jack stands.


  • Use needle nose pliers and pull the old sensors out. 9 times out of 10 they’ll break, don’t worry you have new ones.


  • Use a nail or a punch to remove the 2 pins that hold in the bake pads and spring.


  • You may have to use pliers to push the pads back and to pull them out.


  • Use your 19mm ” drive ratchet and socket to remove the 2 bolts that hold the caliper to the steering knuckle.


  • Hang the caliper by a old wire coat hanger from the torsion bar. Never let it hang by the brake hose.


  • Use a flat head and a hammer to remove the dust cap..


  • Use a 5mm hex socket to loosen the bolt, don’t remove this bolt, just loosen it.


  • Unscrew the bolt from the spindle


  • Then the bearing will fall out, looks yummy. Then pull off the rotor.


  • This should be what your left with.


  • Use 2 or 3 lug nuts and bolt the rotor/hub back to your tire


  • Use your 10mm hex socket with ” drive to remove all 5 bolts, there on there pretty tight.


  • Remove the hub and rotor and hub from the tire. The hub should come apart from the rotor, just hit it with a hammer if it doesn’t. Then bolt the hub to the new rotor and put it back on your tire and tighten the bolts to 84 Ft. pounds. Use blue locktight.



  • Slide the rotor/hub back on the spindle.



16 slide the bearing back in after you have packed it with grease. Screw the big nut back on and tighten it then back off until you feel it break free(about 1/3 of a turn to the left). You don’t want to much pressure on the bearing or it will not spin freely. Then snug down the 5mm bolt.


  • Hit the dust cap back on and then put the caliper back on using lock tight on both bolts and torque them to 84FT pounds.


  • Apply brake paste to the back of each pad.

18 push the piston in the calipers back and slide in the new pads.



19 Snap in the new sensors your done.




I hope this will be of help.

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1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg

Last edited by 79Mercy; 11-02-2008 at 10:00 PM.
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  #2  
Old 11-02-2008, 07:46 PM
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useful
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  #3  
Old 11-02-2008, 09:06 PM
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Another great post for everyone.

Dave
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  #4  
Old 11-02-2008, 09:27 PM
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I'm a bit disappointed at the omission of the following points:

1) The inner wheel bearing was not removed and cleaned and repacked.

2) The outer wheel bearing was removed, but not cleaned and repacked.

3) The contact surfaces where the pads ride on the calipers were not thoroughly cleaned and greased.

4) The setting of the clearance via the hit or miss method is fraught with risk for a new mechanic who has never done it. If the bearing is tight, it won't last 1000 miles.
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  #5  
Old 11-02-2008, 09:33 PM
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1. true
2. It was re-packed
3. I used the pad paste and cleaned up the pistion before pad insertion.
4. ????, the bearing isn't tight.
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1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg
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  #6  
Old 11-02-2008, 09:44 PM
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Quote:
Originally Posted by 79Mercy View Post
1. true
2. It was re-packed
3. I used the pad paste and cleaned up the pistion before pad insertion.
4. ????, the bearing isn't tight.

2. All well and good.........but, the casual observer won't catch it or understand it.

3. The pad paste has nothing to do with cleaning the caliper slides with a stiff wire brush and adding brake pad grease to the slides.

4. For you..........maybe............for others..........it could be.
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  #7  
Old 11-02-2008, 09:45 PM
85 DSEL's Avatar
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Thanks for this posting as I will most assuredly save it in my "How-to" folder for safe keeping. This job is one I will likely do in the spring or early summer!
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  #8  
Old 11-02-2008, 09:46 PM
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Quote:
Originally Posted by Brian Carlton View Post
4. For you..........maybe............for others..........it could be.
I was instructed when isntalling the bearing retaining clamp/bolt that one should tighten it and back off a hair so the bearing will spin freely
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  #9  
Old 11-02-2008, 09:48 PM
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Quote:
Originally Posted by TheDon View Post
I was instructed when isntalling the bearing retaining clamp/bolt that one should tighten it and back off a hair so the bearing will spin freely
Use a dial indicator just once and you will see how absurd that procedure really is.
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  #10  
Old 11-02-2008, 09:50 PM
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Quote:
Originally Posted by Brian Carlton View Post
2. All well and good.........but, the casual observer won't catch it or understand it.

3. The pad paste has nothing to do with cleaning the caliper slides with a stiff wire brush and adding brake pad grease to the slides.

4. For you..........maybe............for others..........it could be.
3. Im not having any problems yet so I must have done it correctly.

4. I promise, it isn't to tight. I tightened it and then backed off until I felt it break free and then tightened the 5mm bolt.
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1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg
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  #11  
Old 11-02-2008, 09:55 PM
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Quote:
Originally Posted by TheDon View Post
I was instructed when isntalling the bearing retaining clamp/bolt that one should tighten it and back off a hair so the bearing will spin freely
The problem with such a description is that nobody can define "spin freely". You back off the nut so that you think that it "spins freely". But, in reality, it needs to back off another 1/16 of a turn to truly release all preload. You don't know this because you didn't back it off the extra 1/16 looking for the point where all preload is released.

The description is fraught with risk and ought to be expanded if one must use the Chevy way of tightening a wheel bearing.

You are aware of the FSM spec of .0005" axial play.........correct?
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  #12  
Old 11-02-2008, 09:58 PM
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Quote:
Originally Posted by 79Mercy View Post
3. Im not having any problems yet so I must have done it correctly.

4. I promise, it isn't to tight. I tightened it and then backed off until I felt it break free and then tightened the 5mm bolt.

I'm not criticizing your own work. I don't know how successful you were with it. But, others will have problems with the description and the technique and I encourage you to modify and add to it if you want to provide an accurate document for the future.

I wouldn't consider it a candidate for the DIY profiles in this condition.
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  #13  
Old 11-02-2008, 10:11 PM
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whatever
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1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg
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  #14  
Old 11-04-2008, 11:32 AM
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Hmmm

Quote:
Originally Posted by Brian Carlton View Post
2. All well and good.........but, the casual observer won't catch it or understand it.

3. The pad paste has nothing to do with cleaning the caliper slides with a stiff wire brush and adding brake pad grease to the slides.
These are not floating calipers = there are no slides.


Quote:
Originally Posted by dmorrison View Post
Your talking a about the inward and outward movement of the bearing assembly once the assemble is tight. The attached photo is how you set up the dial gauge and base to measure it.

This post shows how it is set up on the rear wheels. Same philosophy on the front wheel.

http://www.peachparts.com/Wikka/W123RearWheelBearings

Limits for the front wheels are

.01-.02MM

SAE 0.00039-0.00078 inches

So on your dial it's 4/10ths of a increment to 7/10ths of an increment.

Dave

Wheel bearing
Wheel bearing

FYI DATA EDIT:
0.01 millimeters is equal to 0.0003937008 inches
0.02 millimeters is equal to 0.0007874016 inches.



Have a great day.
Attached Thumbnails
How to guide to replace front Brake Pads and Rotors on a W123-front%2520wheel%2520bearing%2520play_sdrth86767.jpg  
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Last edited by whunter; 11-26-2008 at 11:04 AM.
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  #15  
Old 11-04-2008, 11:37 AM
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Quote:
Originally Posted by whunter View Post
These are not floating calipers = there are no slides.





Take a look at the calipers where the pads ride. There are four machined pads on each caliper half that have a good surface finish. The backing plates contact these points and slide against them as they move toward the rotor.

One of the principal reasons for poor braking is the binding of the backing plates against these rusted and very poorly maintained surfaces.

The reason that the pads are difficult to install is the failure of the owner to clean these surfaces and grease them.


Oh, and.......have a great day.

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