Walk me through a caliper rebuild

I was working on the car today and the left front caliper is leaking (it was oily on the lower half and the outer o ring was tore up pretty bad). The right looked ok, but that o ring was rough looking too (no leaking oil). I think a need to rebuild both (want to do this to save money for challenge budget).

The Haynes manual is on the way. Any tips on how to do this? I'm starting to get my wrenching confidence back after many, many years of paying other people to do things. All advice appreciated.

FYI, 1985 RX-7, 12a, disks all around.

Thanks,

J

Clean it, disassemble it, make sure it's all shiny and clean, and slap it back together. A touch of brake fluid on the new seals will insure that it slides together nicely without tearing.

If there is any corrosion in the bore, forget about it and get a new one. You could hone it out, I guess. They make the tools, I've never tried it though.

Don't know anything about working on an RX-7, but track down some rubber grease for the seals.

I rebuilt my calipers on the Mini because new/rebuilt ones are big $ and rebuild kits are cheap. Replaced pistons and all seals. It wasn't too hard. For my 2002 I just bought rebuilt calipers as they were relatively cheap compared to the rebuild kit.

I've done a few. Use compressed air to pop the piston out, but make sure your fingers are nowhere near the piston when you do that. The rear calipers on the Esprit required a special tool to push the caliper back in. This tool came with my rebuild kit from one of the major Lotus parts suppliers. I think the caliper was used on Renaults. Mazda calipers probably don't need one.

Next time I take a system apart, I'm going DoT 5 fluid when it goes back together.

Get a FACTORY rebuild kit. (Hint: there are no Mazda/ATE/Aisin factories in Mexico) ;)

Pull the caliper off...plug the brake line fitting. Don't retract the piston first. The fluid in the calipers is the nastiest stuff in your brake system. Don't press it back up the brake hose if you are going to rebuild anyway.

First...clean the outside with a wire brush then brake cleaner. Once it's dry, paint it. Since you're replacing the boot, you don't have to worry about masking anything.

Then stuff a rag in front of the caliper and apply a little bit of compressed air with a blow gun...just a little, because that sucker will leave the caliper at terminal velocity.

Rip off what's left of the boot and then take a pick or a knife and remove the old retaining ring.

Clean the bore with a clean rag soaked in clean brake fluid.

Replace the o-ring on the caliper. It should be lubed with the pink moly soap that is included in the rebuild kit.

Put a little bit of brake fluid on the new retaining ring, and work it around the boot until it seats...it's a little fiddly, but you'll figure it out. No tools, you'll rip the new boot.

Done. Bleed it good.

This is one of the best ways to spend $50 on a used car.

One more tip...brake fluid soaks through your skin and damages your kidneys. Wear latex gloves.

My .02c I also used a 3 stone hone to get the bores perfectly clean. Have stood up for 3 years perfectly

I'll save you the money on the haynes manual. The instructions will go something like this:

Remove caliper.

Rebuild caliper.

Installation is the reverse of removal.

In reply to Jeff:

Bottom of the page for the front rebuild kit:

http://mazdatrix.com/j-1brake.htm

Halfway down the page for the rear rebuild kit:

http://mazdatrix.com/j-2brake.htm

When you disassemble the caliper, make sure there's no pitting or scarring on the piston. If there is, replace it before rebuilding. When you clean the piston, be gentle and don't use anything too abrasive. Any pitting can allow the piston to tear the seal resulting in a brake fluid leak later on.

Use nothing but new clean brake fluid as lubrication when reassembling seals/piston.

Use caliper slide grease when assembling the sliders. If the sliders are rusted or pitted, you can replace those beforehand as well. Check the tolerance between the sliders and their bores, if the slider isn't tight in the bore, that can result in very uneven pad wear.

You might consider replacing the rubber hoses at the same time.

• eleventy billion on the "caliper piston as projectile"...

Compressed air helps with installation as well as removal of the piston. Getting the new boot to flop around the piston on installation is a huge pain in the ass, compressed air makes it less so.

• install new seal and boot into the caliper housing, lube lightly with new brake fluid
• mount caliper in vice and feed a slow trickle of compressed air into the inlet hole
• press piston against the boot to form a seal, wiggle piston and adjust air stream so that the boot flares open and over piston
• immediately stop feeding air and slide the piston fully into the caliper body

I'll have to make a video of this, once you get the hang it only takes a second.

Thanks for the advice, particularly about the fingers!

Rebuild kits are on order.

J

Instead of blowing the piston out with compressed air, use a grease gun -- put a zerk fitting in place of the bleed screw and plug the inlet pipe as necessary.

No projectile problem. Then, of course, clean out all of the grease you just injected ;-)

Matt

Treb wrote: Instead of blowing the piston out with compressed air, use a grease gun -- put a zerk fitting in place of the bleed screw and plug the inlet pipe as necessary. No projectile problem. Then, of course, clean out all of the grease you just injected ;-) Matt

I only do that as a last resort on British cars. When air doesn't work. The grease is too hard to clean out of the calipers and I usually have to split it open.

Video illustration of using compressed air to seat the piston in the boot:

http://www.youtube.com/watch?v=brTPKQcWG0Y

It wasn't OIL leaking out of the caliper. Never use the term "OIL" when talking about brake fluid, because when your kid hears that, someday in the future he will pour actual oil in the master cylinder, and then you will cry. And learn all about rebuilding/replacing the entire braking system.

Sorry, its one of those things that bugs me.

$2010 rules said: F) Rubber or steel brake lines, master cylinders, rotors, drums, brake cylinders, calipers and brake pad linings may be replaced with new stock pieces.

calipers dont count to the budget