Help-Rear Brake Not Releasing After New Pad Install
 

A friend and I put on new NAPA rotos and Axxis ULTs last night front and rear. We pumped the brakes and went for a spin around the neighborhood doing some bedding. It drove great! Was thoroughly impressed with these pads.

So, went to work this morning as usual and decided to drive home on lunch. Pads began to squeal relentlessly even while driving. Then I smelt the pads. By the time I pulled in my garage i was basically dragging my driver's side rear tire. The brakes had seized.

Long story short, I took the wheel off and began to remove caliper. I was removing rear caliper's 14mm bolt to expose the allen head bolt to loosen pads and remove caliper when brake fluid dripped. Not gushing, one drip. And, the Allen bolt was very wet.

https://www.miataturbo.net/attachmen...ine=1361490104

Do you guys know what I need to do to fix this? Total noob here working on his brakes for the first time.

Thanks

Its gonna need a caliper.

Might as well replace both. They are notorious for freezing up. Both of mine were froze last month on my 91' w/ 69,000 miles

So there's no way to fix it? Like take the pads out and try to move piston and somehow seal leak? I dont see why they would just freeze up out of nowhere. Seems too coincidental it happened after we've been in there tinkering....

Getting rear calipers apart is an exercise in frustration.

Also, if they're corroded, rebuilding them won't help, because the seals won't seal. You have to remachine all the sealing surfaces or they'll just leak.

Trust us, replace the damned things.

THIS. Those adjusters love to freeze up. After retuning your junk ones for "core" charges, you'll be into both for about $100.

Remember to bleed the brakes afterwards.

They are cheap enough anyway.

DO it for peace of mine if nothing else. If you don't it will always be in the back of your mind.
Plus you can't reuse it, it's seized, lol!

I had mind stick in the open position. That's how prone they are to seize. I had to sawzall the bracket off to get the core returned. I couldn't even beat it off, with a BFH.

The pistons in my calipers had huge craters in it. very common problem on these cars... Replacing them is the way to go. mine were $80/ea but like others have said a pair can pobably be had for around $100

Have you ever replaced rear brake pads on a Miata before?? Did you completely back off the allen head adjuster bolt before you installed the new pads? Did you follow the procedure described in the FSM (Factory Service Manual) for properly adjusting the caliper piston after installing the new pads?? It is very easy (ummm...been there and done that) to over tighten the caliper piston adjustment and cause the pads to drag if you don't properly secure the rotor with the lug nuts per the FSM. After you've driven around with the pads locked to the rotor, the entire caliper will get overheated. I've never had a caliper leak after botching the pad adjustment but I have ruined a set of new pads.

The Miata rear caliper is a relatively simple, single piston floating design that is simple to rebuild (if the cylinder is not pitted or scored). The adjuster can also be completely disassembled and cleaned (search Miata.net and you will find a tear-down and re-assembly article). My stock rear calipers are 23 years old, have 91K on them, don't leak a drop of fluid and still work just fine. I've got a RockAuto.com rebuild kit for them but haven't needed it yet. You can buy a rebuild kit and new caliper pistons (if needed) for a lot less money than buying reman calipers. If you change your brake fluid on a regular basis, you won't have any problems with rusting caliper bores.

If this were done at a shop, I would accuse them of crushing the piston back with a C clamp before they read the manual and found the allen gear. I imagine 50% of of rear caliper failures have something to do with that mistake.