Odd Brake Noise/Feel after rotor install?

[infernosg]

It seems like every time I finally get a noise fixed another pops up...

A couple weeks ago I installed some new Power Slot rotors on all for corners. I couldn't get a number of the set screws out so they were burned out with a torch at a local brake shop. Ever since then the brakes have been making some really low crunching/thumping sounds as I come to a stop when applying anything more than "moderate" (read: normal) pressure. Also, I've noticed that, while at a stop, I can push the pedal all the way to the floor with decent, but not excessive pressure. I'm not really sure if this is something new or just in my head because I switch from driving the RX-7 and a '09 Tacoma.

From what I can tell the master cyliner, brakes lines and calipers are not leaking as I'm not loosing any fluid. Regarding the brake "feel" I'm leaning toward old, water-filled brake fluid (has not been changed since I've owned the car) or possibly a dying the caliper. I'm not really sure what's causing the noise...

[Pete_89T2]

Need some more specifics to help you diagnose... You're in the 2nd gen section, so I'll assume it's an FC we're talking about. Are these the 4-piston calipers or the single piston sliding caliper type up front? The sliding rear calipers on FC's are all very similar design, except the turbos & some of the NA models get vented rotors - which do you have?

Anyway, my 1st guess in either case is one or more sticky calipers. That could cause the pedal feel you describe, and possibly the noise. If you've got the 4-pot calipers, one or more pistons could be sticking in the bores; if it's the sliding single piston type, the slider pins can get jammed up with corrosion.

Also, I'd find another brake shop - it's much smarter (and easier) to drill out those stuck set screws that torching them. Torching risks warping the rotors among other things.

[infernosg]

^^^ Yep, FC. A 1989 GXL to be exact (I post in the correct sections ) so it's got the front 4-pots and the vented rears. Regarding torching them it didn't really matter to me because I was ditching the rotors anyway. Is there an easy way to check for sticky calipers? I imagine I can just remove the pads and have someone pump the brakes while I watch the pistons move?

The problem I have is I'm deaf in one ear so I can't hear direction so I have no idea where the sound comes from. To me, it seems like it's coming from the rear, but you never know, LOL.

[vex]

Swap out your fluid, check for rotor wear on each corner after driving it for some time. If you're able; take off the calipers and verify proper action. More to the point, I think Pad wear, Rotor wear, and close physical inspection of the calipers will give you a better understanding of what's going on.

Having your pedal go to the floor is not a good sign, but I think should be easily remedied by flushing the fluid. Note any particulates in the fluid as it may be an indication you'll need to replace lines, cylinders, or any other number of the hydraulics.

Also verify that the rear calipers are not locked or improperly adjusted e-brake, as wear may be a significant result--though if you're pads or good you'd know if your rear was grabbing too much.

[Pete_89T2]

Originally Posted by vex

Swap out your fluid, check for rotor wear on each corner after driving it for some time. If you're able; take off the calipers and verify proper action. More to the point, I think Pad wear, Rotor wear, and close physical inspection of the calipers will give you a better understanding of what's going on.

Having your pedal go to the floor is not a good sign, but I think should be easily remedied by flushing the fluid. Note any particulates in the fluid as it may be an indication you'll need to replace lines, cylinders, or any other number of the hydraulics.

Also verify that the rear calipers are not locked or improperly adjusted e-brake, as wear may be a significant result--though if you're pads or good you'd know if your rear was grabbing too much.

Roger all of the above. WRT the rears, take a close look at the relative thickness of the inboard & outboard pads - if they are not almost the same thickness, that's a sure sign that your calipers have been sticking. This is a common problem, especially if you live in an area that uses road salt or is humid/wet. Since the fluid has been neglected for many years, there's a good chance all four calipers will need a rebuild/replace anyway (old water-laden fluid causes corrosion) and you'll need to flush the entire hydraulics system and bleed your brakes when done.

Rebuilding the front 4-pot calipers is easy; kit from Mazda costs < $40 for both wheels. Rear calipers are a bit trickier to rebuild, especially if the sliding pins are jammed - in such cases I'd recommend just buying a rebuilt caliper from a reputable reman source to save yourself lots of time & frustration.

[josh18_2k]

ive had my front calipers "crunch" intermittenly, and brake pedal level would kinda vary. i never figured out what it was, but new calipers fixed it.
my best guess was a piston was sticking, sometimes

reman'd 4 piston calipers are only ~80 bucks at napa.

[infernosg]

Thanks for all the advice. I will be flushing/changing the brake fluid, and installing stainless steel brake lines and new pads this weekend. Before I do anything though I'm going to be sure to check the operation of the calipers.

The current fluid is a little cloudy (not clear/amber) but not overly contaminated. I didn't see any water or air bubbles or particulates in the M/C bottle but you never know. I'm going to pick up one of those Motiv pressure bleeders and do all the cars next weekend.

[classicauto]

Pedal going to the floor = BADDDDD!

That is either (order of likelyhood):

-Master cylinder (wouldn't be leaking, the problem is the fluid bypassing the cylinder when you press the pedal because the bore/cylinder are worn, thus a low pedal with no or very little brake pressure)
-Boiled or watery brake fulid
-Bad caliper(s) (they would be leaking)


As far as whether any brake parts are sticky or not, DON'T pull the pads and have someone step on the pedal. You will likely shoot the piston out of the caliper with the removed pads. You can check the freeness of the piston a number of ways:

- Rotor and pad wear. Is it even? Are the pads tapered? Is one side worn significantly more/less then the other?
- Remove the caliper, compress the piston(s). Is one harder to compress then the other? One stuck?


I would be seriously worried about that progressive pedal though. The only way the pedal can reach the floor is either by a leak, or a worn master. And either of those spells imminent fail. If the pedal goes low, but you can pump it and it get stiff (and stay stiff!) there's likely air in the lines.

[infernosg]

I just wanted to update this thread. I swapped in some new Hawk HPS pads and Mazdatrix stainless steel brake lines on all four corners and flushed the brake system with some generic DOT4 fluid (Prestone, I think) and then bled it with a pressure bleeder. The noise I mentioned in the first post is now gone. I did notice the upper pad spring on the front driver's side is missing, the front shims were installed upside down by previous owner/shop (correct now) and the rear shims are missing completely, but I don't know if any of that has to do with anything.

That being said the brake feel still sucks. When the car is off I can pump them and they get nice and stiff, but as soon as the I start the car the pedal will slowly go to the pedal stop (not the "floor"). Based on this info, I'm with classicauto above; a bad master cylinder, so time to replace that next. Does anyone know how the AAS has anything to do with the MC? I see variants listed "with" and "without" AAS and/or ABS (I know I don't have ABS) but I don't know how it matters. The AAS has been removed/disabled on my car for a while now.

Also, does it matter on which side of the rotor the low pad squealers are located? I think stock has them on both sides but the Hawk's only have them on one. The previous pads had them on the inside of the rotors, which is where I put them, but given the information above, I have no idea if this is correct.