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.

http://i42.photobucket.com/albums/e3...Picture003.jpg

• 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.

http://i42.photobucket.com/albums/e3...cture006-1.jpg

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

http://i42.photobucket.com/albums/e3...Picture007.jpg

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

http://i42.photobucket.com/albums/e3...Picture008.jpg

• Use your 19mm ½” drive ratchet and socket to remove the 2 bolts that hold the caliper to the steering knuckle.

http://i42.photobucket.com/albums/e3...Picture011.jpg

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

http://i42.photobucket.com/albums/e3...Picture012.jpg

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

http://i42.photobucket.com/albums/e3...Picture013.jpg

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

http://i42.photobucket.com/albums/e3...Picture015.jpg

• Unscrew the bolt from the spindle

http://i42.photobucket.com/albums/e3...Picture016.jpg

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

http://i42.photobucket.com/albums/e3...Picture017.jpg

• This should be what your left with.

http://i42.photobucket.com/albums/e3...Picture018.jpg

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

http://i42.photobucket.com/albums/e3...Picture019.jpg

• Use your 10mm hex socket with ½” drive to remove all 5 bolts, there on there pretty tight.

http://i42.photobucket.com/albums/e3...Picture020.jpg

• 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.

http://i42.photobucket.com/albums/e3...cture021-1.jpg
http://i42.photobucket.com/albums/e3...cture022-1.jpg

• Slide the rotor/hub back on the spindle.

http://i42.photobucket.com/albums/e3...Picture023.jpg

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.

http://i42.photobucket.com/albums/e3...Picture026.jpg

• 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.

http://i42.photobucket.com/albums/e3...Picture003.jpg

• Apply brake paste to the back of each pad.

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

http://i42.photobucket.com/albums/e3...Picture029.jpg

19 Snap in the new sensors your done.

http://i42.photobucket.com/albums/e3...Picture030.jpg


I hope this will be of help.

useful

Another great post for everyone.

Dave

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.

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.

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! :)

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.

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.

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?

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.

whatever

Hmmm
 

These are not floating calipers = there are no slides.



Wheel bearing
http://www.peachparts.com/shopforum/diesel-discussion/148772-wheel-bearing.html

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.

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.

Hmmm
 

That is not a slide, it is the brake pad guide = sloppy fitting box.
Vehicles in no salt/snow locations, generally do not need to clean this area = no corrosion.

Excess coating on cheap/sloppy aftermarket parts is a very common reason brake pads are difficult to install.

I'm going to have to side with Brian on this one.
You did a great job with the tutorial & we appreciate your effort.....but

The factory shop manual gives specific measurements to make sure it's done right.
It's like the difference in checking timing stretch by lining up the cam marks or checking at 2mm valve lift. Will the other way work? Sure it will. Will the masurements be accurate? Who knows.

Using a dial indicator on the rotor isn't hard at all.

Also I don't care what car your working on brake components need to be cleaned & greased. A can of brake cleaner goes a long way.

Danny

If the backing plates slide against it.........the term "slide" would be appropriate. If you want to call it a "brake pad guide", be my guest.

All vehicles need this area cleaned of rust and corrosion unless you've figured out a way of keeping water and dirt out of that area.

If you don't clean the slides, the pads typically won't install without force. If the pads are binding, you've got brake problems.

If you're ignoring this important maintenance requirement during a pad overhaul, you're making a critical mistake.

If you want to characterize Textar pads as a "cheap aftermarket pad" ........be my guest with that as well............

This is a good write up for those who were thinking this job is near impossible.

Lets see... 18,000+ posts vs 7800+ posts vs 3500+ post vs.......:D ..... hmmmmmm......;):D

.... i guess since we're nitpicking.... how about the "how to" on pressing the calipers back.... thats a trick in itself..... vs 1500+ posts.....:D

Hi, Roy!! How ya doin'?

I'm not sure how the number of posts someone has here relates to their knowledge level about specific repairs.

Precisely true.

However, I pride myself in restricting my comments to those tasks for which I have personally completed and have specific knowledge.

This is one of them.

Just lightening the mood folks..... :)

I was getting a little tense reading this thread. Probably should thank 79mercy for his efforts and desire to be of help. Many of us have played with various issues on our cars and am sure have some amount of expertise in one area or another.

Others can probably address repairs with theirs eyes closed since they are so good and have done so much of it..... and some of us learn something new everyday. Some have tried things that others don't even want to attempt.

But whats great about this forum is that everyone always tries to help:) But I do recognize that those who have been around doing it longer must have more knowledge than me..... if that is wrong then I stand corrected:)

it does read a bit like a Nikon forum.

I've seen the MB special tool for pressing those calipers back. Looks a bit like a duckbilled channel locks.

I used a old edger blade wrapped in a towel to push the pistions back.

I bet that wasn't in the FSM either, but it worked great.

Whats wrong with Textars? :confused: I use them. Other than being a little dustier, I think they're a fine pad.

Brian is correct, in my opinion, about greasing the side , not slide, of the pad. See picture one for greasing the Bendix caliper pad.

Second, setting the bearing torque should really be done as per the manual. Or as I have shown in the post below for the rear bearing. Use the same technique for the front.

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

The second picture shows the manuals method for setting the bearing torque.

Dave

Hi
 

Going slowly nuts balancing work with getting ready for the Texas tech session. :D
I don't want to forget any parts or tools, the drive home is to long, twenty hours straight through driving each way. :eek:

Ok
 

The brake pad guide does need to be cleaned/lubricated in most cases.

Note: Depending upon corrosion level cleaning can be ...
* Light = stiff wire brush
* Medium = light application of sandpaper
* Heavy = hammer, chisel, and files, the caliper is generally (damaged) not functioning correctly at this point = needs rebuild.

:( Here in Michigan the corrosion is frequently HEAVY = replace the calipers.

:) I did not name a brand because many members use the lowest cost pads from their preferred supplier.

It's in the Wiki
 

Thanks 79Mercy!

This DIY has been added to the Wiki HERE.

I also added a warning at the end that refers readers back to this thread so they can read the member comments here.

Thanks for this, I'm about to do this same job tomorrow.

I'm needing this car back on the road *NOW* so I won't be cleaning/repacking the wheel bearings but I will at some point (next week probably) soon. I'd like to have seen a couple steps about pulling the inner bearing/seal and cleaning/repacking. I'm also concerned that if I hadn't already asked a bunch of people about how to set the bearing tension that your method would tend to influence me to set them too tight.

I'm an instructor and the big thing I've learned (sometimes the hard way) is that people will misconstrue EVERYTHING you say. Its so important to be precise..

Also saying "whatever" when somebody gives you constructive criticism is just rude. I applaud you for your effort but theres just a couple little things that could make this writeup awesome (the pics are great btw!).

why? I said snug it down and then turn the nut to the left until you feel it break free, then snug down the nut.

As for the rear bearing seal just pry it out with a flat head, its going to break so just buy a new one.

This is a recipe for disaster. The bearing sits right behind it and the temptation is to use the face of the bearing for leverage. You cannot "pry" the seal from the hub..........you must "pull" it.

A seal puller also tends to use the bearing for leverage.

I never used the actual tool, but the leverage on the bearing doesn't seem to be a very good design. I've damaged the face of a bearing using leverage and would never advise anyone to approach it that way.

Far better to hook the seal and provide a vertical impact force on the "hook". Do this several times around the seal and it moves forward and out without any bearing damage.

Just bumping this thread, where do I get a dial indicator? Went to the local auto parts stores and they don't have it...tried Autozone, Pep Boys, Kragen, no go.

Try these guys.........good prices for less than "professional" tools:

www.use-enco.com

Answer
 

Here are two suppliers I use all the time. :D

https://www.harborfreight.com/search?q=dial%20indicator

https://www.harborfreight.com/clamping-dial-indicator-63656.html

http://www.wttool.com

http://www.pts-tools.com

Thanks, I found one at Harbor Freight and there's a store on my way home from work. Since I'll be doing the brake job tomorrow I might as well just pass by there. Hope they're open after 5, just in case!

Edit: What's the best way to remove the inner bearing? Instead of repacking I just bought new ones for peace of mind. SKF a good brand?

this should read the Inner bearing seal... anyway, here's what I have done for years professionally and at home. it always worked for me, and it DOES NOT DAMAGE THE SEAL OR THE BEARINGS... if done carefully.

after you have popped out the outer bearing and set it in the dust cap, put the lock nut back on loosely, now gently pull the hub over the nut and rest the inner bearing against the lock nut, now slide the hub on a bit then pop it out against the nut. this will force the inner bearing race against the surface of the grease seal and pop both out of the hub.
********************************************************
warning!!! if not done correctly, you can damage both the inner bearing and the race of the inner bearing. so fully inspect both after the bearings are out, and be prepared to drive out the race and replace the bearings, race and seal. !!!
*********************************************************

you should then clean thoroughly, the inner, outer bearings, and completely remove all traces of grease from the hub, and the spindle. unless you are absolutely sure you have exactly the same brand and weight of grease as what is already in there. most high pressure greases do not mix well...
then re pack the bearings with your preferred grease and pack a thick layer of grease inside the hub. DO NOT FILL THE HUB WITH GREASE!!! just a layer around the inside of the hub.

...........and, without great knowledge and care, it will not be done correctly............

This procedure is fraught with risk...........I wouldn't advise it for anyone but a professional.

That is a good way. I have used big channel locks also.

I have also used a small cold chisel to bend the seal inward, but parallel to the bearing so I could get a flat head and pry it up against the lip of the hub.

Won't that damage the seal?

Wouldn't the preferred method be to open the bleeder on the caliper before depressing the pistons for pad installation? I am of the opinion that the brake fluid that has been exposed to the most heat and has the most probability of containing contaminants such as water would be nearest to the caliper. I certainily wouldn't want any possibly contaminated fluid pushed back up into an ABS controller as installed on my W126. Another point is if the master cylinder reservoir has been topped off between pad changes, when you go to push in the caliper piston to install the pads without opening the bleeder the possibilty exists that you may get some brake fluid shooting back through the hole in the top of the reservoir cap. Just my 2 cents..:cool:

When he states "inward", he means toward the centerline of the hub..........not parallel to the axis of the hub. To force the seal inward is diffcult because the chisel needs to bite into the surface of the seal and puncture it. Then, the seal can be forced "inward"..........and not "downward".

If you can damage it and force it inward, you'll be able to get a prying instrument on the hub to lift it upward without prying on the bearing.

screw drivers weren't made for prying... Pick up a set of prybars from HF

If you replace the seal what does it matter if you destory it in the removal process?

oh just the seal then pry with a screw driver.. I thought you were talking about something else.

Something isn't right....... hahaha

79Mercy, thanks for taking the extra time to post the pics for this job. Yeah so some folks here said you may have missed some steps or they would have liked to see some things done differently. Don't let them discourage you from posting some more DIY pictorial threads. These help everybody and it's the discussions and interjections that follow the initial posting where you can really learn further and gain knowledge on how you want to go about and tackle the job yourself. What I'm getting at is that every body here obviously has a passion for the cars we drive and try to maintain but everybody doesn't have the same skill level. You went ahead and did your best. I certainly didn't see anything that you obviously damaged. Would I have done it the same way? Maybe not exactly, but I think I would be better off having you replace my pads and rotors than some hack at a discount brake shop. Thanks again:thumbup: