Bad caliper, or master cylinder going out?

[12guns]

I've had a squeak for quite some time now. It seems to come and go, but I have not been able to narrow down the cause. The squeak is coming from the pad rubbing the rotor every so slightly, and only in one spot on the rotor. Rotors are not warped, they are smooth and quiet. I had them super hot towing a boat and they have no uneven deposits either. So, the pads are clearly not fully releasing from the rotor as fast as they are supposed to. After a few mins of driving, they release and the squeak goes away. Oh yeah, pads are fine. Lots of life left.
Could this be a frozen piston in the caliper? Or could that be a sign that the MC is not working right? I flushed about 75% of the old fluid out w/ new Dot 4 sythetic, bled the brakes on all 4 corners, and problem is still there.
Thanks for any help!!
If it turns out to be calipers, I may be in the market for new calipers and some yellow stuff pads!!!

 

[super90]

Clarifying question: How do we know the rotors are not warped? What data do we have that allows us to draw that conclusion? Has the runout been tested?

Just curious.

 

[12guns]

Clarifying question: How do we know the rotors are not warped? What data do we have that allows us to draw that conclusion? Has the runout been tested?

Just curious.

I guess I don't really know they are not warped...reason I think they are fine is because they are smooth as silk hot or cold. I have been in the hills, towing heavy boats and such and have never once felt the pulsing or juddering of warped rotors or uneven brake pad deposits. I guess I should start there to ensure they are not warped, but wouldn't I feel it if they were?

 

[APKhaos]

Doubt you'd feel the little bit of runout it takes to make a pad chirp. A dial gauge will show it though.
Its also possible the one or more piston seals have hardened up enough to be holding the pad out. Replacing the seals is a simple enough job, and a lot less spendy than replacing the calipers.

 

[Shane Drummond]

I had a squeaking noise coming from my front right, but had changed pads about 13,000 km before hand, I Checked the discs and found a groove starting up so pulled off the tyre & caliper assembly and found that my disc pads were worn down enough to need replacement... Lead foot I guess... I noticed the thin plates that hold the pads in place like clips were touching the disc, and sharpening up as i drove, when i brake, the squeal went away... So I found a new set of pads and changed out the short lived previous pads... 2 to 3,000 km later and the squeal is back...

 

[uHu]

Not unlikely frozen piston in caliper. They tend to get a bit harder to move over time - particularly with salted roads. Where in the (new) world are you?

 

[Gottagetone]

Why would you need a new caliper when you can pull em apart and grease up the pistons?

 

[LXRunner]

As well check front wheel bearings adjustment for excessive play.

 

[12guns]

I will check wheel bearings again just to be sure, but I'm 90% sure it's brake related. Squeak goes away when I touch the brakes and with time off the brake pedal, regardless of speed.
Only way I've checked the bearings is with up/down and side/side play, which is non existent. They are also quiet and smooth, and based on the marks on the bolts and the way the rest of the Cruiser was taken care of prior to me owning it, I assume they have been repacked recently. I'll check one of these days when I'm bored and go ahead and repack them. I will however wait until after duck season which will include a good bit of deep water and mud! Looking forward to getting the Cruiser out with the 33's! It should be night and day difference between my old 4runner.

 

[APKhaos]

If you have no play 3 - 9 and 6 - 12, and no noise, the bearings are probably good for quite a while.
Its either a slightly warped rotor or a sticking piston, and my money is on the latter. Simple and cheap to reseal the pistons. Do both pistons, both sides, then flush the lines with new good quality fluid and bleed all four calipers.
Perfect DIY job if you want to get to know your truck better.

 

[100 TD]

I'll put my money on the anti squeal spring clip rubbing on the disk, happened to me.
http://www.toyodiy.com/parts/p_U_2000_TOYOTA_LAND+CRUISER_UZJ100L-GNPEKA_4705.html
47448-60060

 

[12guns]

Update:
I have bled the brakes and replaced all the fluid.
The "squeak...squeak" is not there when cold. It take a few mins of driving/braking for it to start up.
Tonight I pulled both front wheels and took the pins, clips, and pads out, cleaned them, lubed up the slid pins, rebled the front calipers, and it's still squeaking! All 8 pistons moved freely back into the caliper, so I have ruled out a bad caliper.
Since the pads have well over 1/2 material left, I guess I'm down to warped rotors? There are no deep grooves cut into the rotor face, but there is quite a bit of rust around the cooling fins...more that I remember on other vehicles. I'm going to try to add another "W" spring that spreads the pads on the top pin of the caliper prior to spending money on rotors. I'll do pads at the same time as new rotors, but hate to trash my existing pads. I could have the rotors turned, seems like there is plenty of meat on them. My only problem is that when I go to the trouble to pull the rotor, I want to replace it and be done with it.
BTW I'm looking at Bosch Quet Core rotors. I put them on my wife's Accord and LOVE the non corrosive zinc coating and they are only $60 each. As for pads, I'll probably go with EBC Yellow Stuff or Red Stuff depending on cost. If they are too pricy, I may go with Oriely Wagner ceramics. They also are on my wife's Accors and have been the best combination I have run on the past 5 vehicles.
My hope is still that the cheap springs will help pull the pads away enough to get rid of my squeak. Oh, and after a minute or so of driving with out any braking, the squeak goes away on it's own only to come back when I stop.
Any other thought??

 

[highonpottery]

that little "W/M" spring is only about as strong as a paperclip. although it's kinda designed to spread the pads apart, I can't really see it doing much for actually spreading. i'd just replace the pads if it were me. my brakes were squealing all the time and I just swapped everything even though I had a good 1/3-1/2 usable pad life left. for $40-50 in pads, it was well worth not going insane over the noise. (i also decided to just replace rotors at same time since full f/r OEM parts cost less than my quote for just front brakes at dealer) i'm sure you could even take that 1/2 material pads and sand the surface if you wanted to try and see if that works.

 

[12guns]

Thanks for the reply! I agree the best thing to do is swap pads and rotors and be done with it. My problem is after a couple vacation weekends, I'm on a spending freeze for a month or two. And on top of that my wife insists on a trip to Italy next year. I picked up a brake pad hardware kit today from Autozone. It comes w/ the steel shim that the pad slips into. The main reason I got the kit was two fold:
One, it will have two "w" springs that I will add to the existing to see if the ever-so-slight pressure is enough to keep the pads from contacting the rotor in that one spot.
Two: the new steel shim things are designed to clip into the pistons inside the calliper. That makes is more difficult to slip the pad into, but if they are clipped into the piston right, maybe that will also help retract the pads from the face of the rotor slightly. The old steel shims have been bent and may not be holding inside the piston right.
If all that fails, I'll order rotors and pads and be done with it. If and when the rotor were to get pulled for turning, I'll be replacing instead.
The good news was that the caliper's themselves are fine.
I have a telephone interview this evening, but will pull the wheels again tonight.

 

[highonpottery]

yes, replacing those backing plates might solve the issue also. it seems like those little tabs that clip into the pistons like to break off and thus won't keep the pads against the piston when they retract. IIRC when I did my front brakes I had 3 of 4 backing plates with at least one broken off tab.

 

[super90]

I had a warped rotor on my TLC (steering wheel shimmy) and pulled the rotors and had them turned, added Akebono Ceramic pads and put it all together (new bearings installed at the same time). Problem solved. Turning the rotors cost $12 a side and pads were maybe $50. $75 or $80 total. If you have lots of material on your rotors, it's not a bad option. Just something to consider if money is a bit tight at the moment.

Adding all the new brake hardware kit isn't bad, but I am doubting it's the real culprit. The new pins are the most beneficial part of that kit, IMHO.

 

[12guns]

You may be right. Only odd thing is, I don't have ANY wobble or pulsating at high/low speeds with hot/cold brakes. If I did, I would agree to the warped rotors and you may still be right. It's just a faint "squeak" and only at one spot on the rotor on each side up front. As soon as I brake slightly it goes away. The fact that it is only squeaking at one spot as the rotor spins would indicate it's not true or straight, but I would think it would wabble like crazy at high speed braking, and that's not the case. Odd I guess. Either way if my hardware kit doesn't do it, I'll get new rotors and pads and be done with it. Oddly enough, rotors are cheap for our Cruisers, which is a good thing! I didn't get around to it tonight, but tomorrow night I'll see how things go.
I also agree there should be plenty of metal on the rotos to have them turned, but with the excessive rust on the inside cooling fins, I'll feel better replacing them entirely. Yeah, money is tight, but when is it not? LOL I can handle rotors and pads if needed, especially now that I know the calipers are good and I won't be spending that extra money along w/ rotors/pads.

 

[12guns]

Son of a *****! Still squeaks...Added the additional "w" spring and re lubing everything well did pretty much nothing for my problem. I've come to realize the squeak I'm hearing I think is the ever so slight contact that *may* be normal. But in my case it's enough of an old rotor or worn pad to cause a slight squeak on one spot on the rotor. Still could be warped rotor. My plan now is new rotors and pads! Not sure which rotors to go with, Napa can have some here tomorrow, the Bosch are a few days out. As for pads I'll go with a ceramic. I don't care about eating rotors, I just want the best stopping power I can get without a high dollar racing pad.

Thanks for all the replies