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Front Brake Overhaul

by Steve Leslie

 

***DISCLAIMER - Please note that this writeup reflects my experiences only and anyone using it for reference or as a guide, etc. does so at their own risk. You may link to this writeup, but you must obtain my permission to re-post it elsewhere.***

Synopsis
This writeup will cover a front brake overhaul, including: New brake pads, new rotors, remanufactured calipers and bleeding the brakes. Although this work was perfromed on a 97 Cherokee, the basics of a brake job are fairly common to most front disc vehicles.

Parts aquired
All parts were purchased from AutoZone:
Duralast Gold brake pads - $31 for all 4 pads
2 - New Duralast Rotors - $40 per
2 - Remanufactured Calipers - $16 (+$20 core charge) per
Bottle of synthetic brake fluid - $5
Anti brake squeal - $2.50

Tools used
Hydraulic floor jack
Stand jacks
Metric and Standard size sockets, box wrenches, etc.
6" C-clamp
Oil catch pans
Vacuum pump/Brake bleeder

Disassembly
Start by jacking up the front end of the Jeep, support it with stand jacks and remove the wheels. At this point, you'll be left with this:


The first thing that needs to be done is an inspection. The rubber lines should be firm yet pliable and should have no obvious bulges, cracks, or leaks. Also check the hard lines as well as the junction of brake lines. Check for grooves in the rotor surfaces or any other evidence of uneven wear.

Next you'll need to compress the piston back into the caliper so after the new pads are installed, it will fit back over the rotor. While it can be done later (they even make a special tool for it), I do it first because helps the caliper come off easier plus it just gets it out of the way. Besides, why buy a special "caliper-piston-compressor" tool when 6" C-clamp does the job just as well...plus it has so many other uses. Mr. Green


Just make sure that it doesn't crush anything (like the bleeder screw) and slowly close the clamp until the piston is all the way in the caliper. It should move smoothly and you'll end up with a good gap between ythe pads and the rotor when you're done Basically, from this:


To this:


Now you're ready to remove the caliper. The picture below shows the caliper from back. The 2 circles indicate the bolts that need to be removed. In some cases these can be allen heads or even torx heads.


Once the bolts are removed, tilt the top of the caliper away from the rotor to take it off. Be carefull not to twist, yank or kink the attached brakeline.


Once the caliper is out of the way, the rotor should just slip right off the lugs...at least most of the time they slip right off. Depending on how long it's been on there, the type of conditions you drive under as well as the climate of where you live, It might have "grown attached" to the hub bearing and take a little muscle or other persuasion to remove it.


At this point (unless you're replacing them), you should take the rotors to a machine shop to have them turned. Basically, they put them on a lathe and machine the contact surfaces so that they are smooth and even. Not doing this can result in eneven braking, vibrations when the brakes are applied, etc. They will also measure the rotors to determine if they can be safely turned. If they are under the minimum thickness, have excessive lateral runout, etc....you'll need to buy new ones.

Now it's time to remove the pads from the calipers. Here's the starting point.


To remove the outboard pad pull up and slide the clips off of the caliper. Note the location lugs on the pad as well as on the caliper. The new outboard pads will have these as well to help ensure that the pad is in the correct position in the caliper:


The inboard pad is held on the inside of the piston with clips. To remove it just pull away from the piston (towards the outboard side):


If you are not replacing the calipers, skip ahead to installing the brake pads.

Installing calipers
The first thing that needs to be done is the slide bushings need to be removed from the old caliper and installed in the boots in the new one. As the caliper compresses/decompresses and as the pads wear, the bushings allow the caliper to slide on them.

The pictures pretty much say it all on how to get them out.




A closer look at the slide bushing reveals a lip on eiter end that the boot needs to "snap" into. So when installing them in the new caliper, make sure they are snug in their new homes.




Now, onto the brake line. Each new caliper should come with two of these:


When you remove the bolt holding the brakline to the caliper the order will be bolt head, washer, brake fitting, washer. Replace the two old washers with the washers that came with the caliper. I did not get pics of this because I did it quickly (to lose as little brake fluid as possible). Make sure you have a catch pan and if you like your paint job, don't get and brake fluid on it....that stuff eats paint. Here's the bolt that needs to be removed.


Brake Pads
If you were not replacing the calipers, you're in the right place. If you did replace the calipers, go wash your hands and the get brake fluid off them...we don't want that stuff getting all over the brake pads. Mr. Green

First figure out which pad is the inboard and which is the outboard. Then apply some disc brake quiet/anti-squeal to the back of the pad. DO NOT APPLY IT TO THE FRICTION SURFACE!!!. Just put some on the back of the pad and spread it around as evenly as possible.


When complete, it should look a little something like this:


Now, using the opposite of what you did to remove the pads from the caliper, install the new ones (remember to make sure that the location lugs on the outboard pad are lined up with the ones in the caliper):.


After the pads are in, you can install the rotor on the lugs, followed by intalling the caliper. There are tabs at the bottom of the pads that you'll need to line up in order for the caliper to slip on.


Now just reinstall the caliper bolts and tighten to spec. 

 

Bleeding the brake system
So if you didn't replace your calipers (or otherwise open up the system to the air), you're asking why should you bleed your brakes? Just like any other fluid in your Jeep, brake fluid should be changed every so often. One quality about brake fluid is that it absorbs moisture, which not only makes the fluid less effective...it lowers the boiling point. If the fluid boils, gas is released and suddenly there's air in the line. Bleeding every so often (1-2 year intervals) helps prevent this.

There's tons of writeups and methods for bleeding brakes (just do a google search). I prefer to use a vacuum pump. It allows one person to do the job, and there is no necessity to touch the brake pedal, allowing me to watch the master cylinder (it should NEVER be run dry) as well as what is coming out of the system. Also, like the c-clamp it serves other purposes besides just bleeding brakes...it works anywhere you need to create a vacuum. You can pick them up at most autoparts stores for around $50...I think Walmart even sells them.

Some people are going to chime in about speed bleeders which are very sweet and make quick work of bleeding brakes...but if you're like me and have 4 vehicles to maintain, consider buying a set of speedbleeders for each one at around $50 per vehicle. Then compare that to a $50 vacuum pump that has other uses as well. Wink

Anyway, back on point...this is the vacuum pump in the configuration used for bleeding brakes.



A few general rules first, always start at the wheel with the longest hydraulic line to the master cylinder and work around the vehicle to the shortest. For us here in the States it would be right rear, left rear, right front, left front. Never let the master cylinder run out of fluid, so make sure to have plenty on hand. Also, don't re-use the fluid...would you drain the oil out of your engine and then turn around and pour it back in?

The process itself is simple but time consuming, connect the end of the hose to the bleeder screw, use the pump to create a vacuum and then slowly and slightly open the bleeder screw:



Check the master cylinder often and add fresh fluid as necessary. When the fluid runs clear and you see no air coming out of the line, close the bleeder screw and move on the the next wheel in sequence.

After all four corners have been bled, start the vehicle and step on the brake (you might have to pump them to compress the new pads onto the rotors and bring the pedal up), then turn off the engine and hold the pedal down. If the pedal does not sink after 15-20 seconds, you're set. If the pedal does sink, the system should be bled again.

Once that's done, install your wheels and take the vehicle for a test drive, but go easy at first. If something is going to fail, it will most likely be right away. Besides, you don't want to glaze over your brandie new pads. Mr. Green

Stoppin' on a dime,
Steve

***DISCLAIMER - Please note that this writeup reflects my experiences only and anyone using it for reference or as a guide, etc. does so at their own risk. You may link to this writeup, but you must obtain my permission to re-post it elsewhere.***

 

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