Brakes Crunching AGAIN!!!
 

This is really beginning to piss me off. Last year about this time I posted about this unknown crunching sound coming from the brakes when i would apply them. Once out of storage from the winter (roughly a month or so ago) everything seemed fine (mind you I had new brake pads installed and the rotors machined right before putting her to sleep for the winter.
Today I notice that they are starting to crunch again. I say crunch becasue thats the only word I could seem to place on the sound.
Dopes anyone else have this crunching brake noise or has ever had it. Every time I take it to the shop they tell me everything is AOK. So im stumped and its f"^king annoying having a slick clean ass vert and it sounding like a broke ass 80's Honda when I get to a light or stop sign.
any insights?????

about to disown this car
 

with all these irritating stupid noises.

does it do it as soon as you apply the brakes, during braking, right before you stop, etc...?

Wayne
 

all three you listed would be correct sir.
It does it when applying during and when it is coming to a stop. Sometimes even crunches when you just apply the pedal from a stop!
anything sound familiar?

thats really weird, almost sounds like stuff is rubbing. jack the car upon, take the wheel off, and havea buddy sit in it while you spin the front wheel, and have him slowly apply the brake, look to see whats crunching.

to me it just sounds like you got some really nasty gunk/ corrosion going on in at least one caliper...the piston is "hopping" instead of sliding smoothly...bleed all four calipers (about 20 pedal "strokes" each for the rears, and maybe 10 each for the fronts, while keeping the resevoir full w/ new fluid), and see if that helps...

I think waynes got it right, take one caliper off and pop the pistons out. (I had realling nasty gunk in one of my calipers, but it didnt crunch) rebuilding them is ind of a bitch to do, but its well worth it.

I have a crunching noise in my brake pedal. It happens when I apply the brakes, lightly, medium, or hard. All I have to do is press the pedal when the car is off. The harder I press the more noise.

It has been there since I bought the car. 90 gtus from the junkk yard. Which I think is the root of the problem. I have rebuilt the car from the ground up. I have a new master cylinder, rebuilt front and rear calipers myself, ss lines, new rotors all round. When I was running hp+ pads the car stopped on a dime, could lock up the fronts at will.

The noise has always been there. It isn't coming from the calipers it is from the pedal, I can feel it threw my foot. The last thing I can think of is the brake booster. The car doesn't have ABS. Since my brakes work so well, it has been pushed back down the list of things to do. But the car does sound busted coming up to a stop sign, even though it isn't.

i noticed mine crunching only after i installed my new Stainless Steel lines from MazdaTrix with Motul 600 brake fluid.
i think that i flushed the system well but i know there is still old fluid somewhere in the system...

I'm sure youre aware of this but I didn't see it posted. Had a friend complain about the same thing. Got his brakes service. New pads, machined rotors. Then all was ok for a month. Then it started to happen again.

So naturally he called my mechanic an idiot yada yada yada. Anways long story short I took a ride with him and noticed one thing in particular. His driving habits. Super super hard on the breaks all the time. Also found out he wasn't aware that you had to break in the brakes.

Again I know its basic and I'm sure your already aware of it. But I thought I'd just make sure.. you have to break in the brakes. So for the first 500 or so miles brake really really nicely. So they can seat correctly.

I was up at the local rx7 shop today. They had a soon to be parts car. I jumped in and pressed the brakes. Very quiet and a better feeling in the brake than my car. None of the mechanics up there had a better guess than me. Which my guess is, in between the master cylinder and the pedal. Something needs to be done.

I will have some time this summer to mess around with it. I will figure it out. Unless someone here has the same problem and fixed it. Then it will be easy.

dp

Take the vac line off the booster & see if you get the same results (braking will be harder, so don't go killing yourself or anybody)...it won't totally rule out the booster, just that part of the system...I've never taken a booster apart, so I don't know if there are seals, springs, whatever in there that could be causing this...

I have an 88 RX7 Convertible with 52000 miles and mine do the same. I thought my brakes were just bad????

The brake booster gets its atmospheric air from where the pedal pushrod goes through the firewall.
Try this:
Engine idling, work the pedal by hand, and spray some WD40 at the pushrod.
The oil will get sucked in the booster & may fix it.
Don’t overdo it.
If a few shots doesn’t help, it’s going to need a real repair job.

I agree, after my car has been sitting for a while it does the same.
So I drive for a couple days carefully...:) It will go away after few rides .

If the car has been sitting for a while and you can hear the brakes when applied it is likely that it's surface rust/corrosion that is wearing off. Get hard on them a few times...

Also, breaking in new pads (especially performance pads) does not require gentle break in. The pads should be heat cycled correctly and this usually requires a few very hard 60-0 stops. I break in pads like this:

-Roll out of the shop and drive forward a few feet, then stop. Roll backwards a few feet, then stop. Repeat this 5-6 times.

-Then, get a nice stretch of road in a safe area and pound out some 60-0 stops. About 4 hard 60-0 stops should get the pads up to the right temps, then drive as usual :)

I have the same problem with crunching in front calipers.

I have rebuilt the master brake cylinder and changed the vacuum booster. Bleeded the brake fluid really well, so there's no dirt in the system. I hear it crunching even with the engine shuted down...

And the weirdest thing is that today we've tried to take off the wheel and look what's wrong there and found absolutely nothing and for that moment with left front wheel hanging in the air only the right front one was crunching... but when we replaced the wheel and jacked other side of the car and took off right front wheel left started crunching and right stoped to do that!!!

there has to be some explanation?!

I need to notice that the car sat down 2 times for more than a year in total...

Any input will be appreciated!

Hey i think i figured out what was crunching!!!

It is a rod that goes from inside of brake booster and connects to a brake master cylinder. It makes sounds because it is rusted! At least it is in my case...

All brake noises has gone after i replaced brake booster with a spare one.

It could also be a misaligned pad spring. My spring got put in wrong when I got my brakes done at Midas. I took it back and they said everything is fine. I took the wheel off and played with the spring position and it is fine now and has been for months.

In my case it is definitely not the spring... it would be too easy...