Fruid

I replaced my front pads and discs (rotors) to get my XJ through its MOT.
Bled them as normal but they keep binding. I have taken the callipers off 3 times now, forced the piston out as far as I dare (removed pads) oiled the pistons which were very clean, still binding and getting hot!

Done the bleeding with the engine running, there are no bubbles at all, clamped the pistons shut right in as well. Both sides.

The only thing I think it might be is the rubber hose collapsing with me taking the callipers off and hanging them up which causes the hose to fold sometimes.

Can anyone help?

MtnHermit

Your post doesn't mention the sliders, critical with any single piston caliper. Did you check the sliders? Do they move freely?

Fruid

Sorry about that. Yes the sliders are good and greased, the callipers slide on them really well.
I have just checked the flexi hoses and they seem totally fine.

After looking closely, with the new pads and rotors and the piston appears to be right the way in they still rub slightly, i wonder if the pads i bought are slightly thicker than normal...basically what has been happening is on a 25mile journey I do with lots of braking because of hills, one of the sides heats up and I think the heat makes the rotors expand even more compounding the binding problem until they start to smoke!! Maybe wearing some of the pad away will help.
My pistons look like your 2nd photo.

MtnHermit

Two thoughts:

1. The rotors should turn freely with no brake pedal pressure. You can take two lug nuts, install them in reverse to simulate a wheel such that the rotor is clamped to the hub. Spin the rotor, should be free after applying the brakes. If not releasing, you may have to file/grind the pads to create a small space.
2. The pads have a notch which slides on a machined vee on the carrier. That notch/vee carries the actual braking force, not the caliper. Is that notch correctly positioned?

I really doubt that the problem is hydraulic, rather mechanical.

DrShaggford

Also check the caliper mounts (I don't know what it's actually called but the part that the caliper actually bolts to and slides on.) Where the caliper slides on this it tends to get notched and mess with brake function. If this is the case you will need to fill the notches will weld(not jb weld) and file it back down to as close to factory spec as possible. Since I've done this my brakes work flawlessly (other than the well loved rotors!)

kennzz05

i have had the hoses collapse and cause just what you describe if they are original than replace them. i replaced calipers and pads just to find out the 7 dollar part was my problem
when u push the brakes the fluid will easily overcome the collapsed hose because of the amount of pressure however it wont allow the pressure to release

weebur

Here's some additional thoughts:
First I'd confirm that your brakes are binding/dragging. When I suspect this problem I drive around the neighborhood braking hard, then just before I pull in the garage I ride the brakes, with my floor jack ready I jack up one or both of the wheels off the ground and try to turn the wheel. If it's hard to turn then there's a problem.

Common causes are that the calipers are not retracting (sticking or binding caliper). Another is the flexible rubber brake hose is weak and swells under pressure and fails to return to its normal size and puts pressure into the caliper causing the pads to drag. The hoses don't collapse. And, I don't think you can see if the hoses are swelling and not returning to their normal size, but you can check for cracks. Now I'm not 100% on whether this applies to our system, but I imagine that if the return port in the master cylinder is plugged it might.

Still another might be that there's excessive wear on the mounting ledges where the pads rest. Most of ours have wear there. And dry/worn caliper pins. There are other less common causes.

Yes the rotors get hot and swell, but in a well functioning system the pistons in the calipers will just recede into their cylinders, when the rotors cool there may be a slight space between the pads and the rotors but that will be taken up then next time you apply the brakes. You should never have to modify the pads. The pistons will retract into the caliper during the install (using a c-clamp) to accommodate any standard pads. New pads will need some time to break in to wear enough for the full surface area of the friction material to contact the rotors. Did you clean your rotors with brake cleaner until they were perfectly free of the protective film? The whole system gets hot and the smoke you're seeing may just be brake fluid or grease from your hands on the calipers and/or the rotors if you didn't clean them well.

I always check the rotors run-out with a dial indicator, even new rotors. I believe the maximum run-out is .005", even new rotors will have some run-out.

If I were you I'd confirm that your front brakes are dragging, then if they are I'd think about replacing your calipers and/or hoses in that order. Best of luck.

Fruid

The brakes are dragging but with the wheels atached you can turn them quite easily, once the wheels are removed you can turn them on the studs just. There is no visible gap between the pads and the rotors.
After say a 2mile up hill journey with no braking I checked them by touching and they are warm but not hot (i used the handbrake to stop).

After 5 miles with light braking they are really hot.
And one journey the nearside got so hot they were pulling the car over when you released the wheel.
Both alloy wheels were covered in black brake dust. Since then I have re-bled them, lubed the pistons and re greased the slides. The car has only done 70K and its a 2000 XJ.
All the pad mounts etc look perfect.
I can't get the pistons to go in any further and I bled them with the G clamp holding them right in.
I am hoping the pads wear away enough quickly to stop the heat build up.
They were fine before I replaced the rotors and pads but they were really worn.

Mgriffico

I have the exact same problem. Did you ever solve it?

Fruid

No not really. The brakes don't get really hot anymore because the pads must have worn away to the correct thickness.
I personally think the pads I bought were too thick, even by 1mm made them bind too much, then the heat made it worse as it all swells up.
I do get a problem with the nearside working better than the offside and it pulls slightly under hard breaking, but I can live with that for now.

MikeT2

I agree with Kennzz05, I had the same problem and I replaced the hoses and all was good. After time the hoses come appart on the inside and act like a check valve which will not allow the caliper pistons to retract after you hit the brakes. When you did your brake job and flexed the hoses it created the problem.
One note: if the calipers with the new pads fit over the rotor and you did not have to force them they should be OK. The pads always ride close to the rotors without any noticeable gap.
Replace the hoses and bingo the problem will go away.
Good Luck

Cherokee40

I had this same problem and found that there was a big blob of grease/oil buildup in the vacuum booster hose from the manifold to the power brake booster. This was removed and my problem went away. You might check that to see if it might be the problem.

Mgriffico

Wow...thanks all for responding.
I should of given you a bit more to go on...i have been putting up with it for over a year now. About 8 months ago i did change the flexible hose....with one like this...

http://www.ebay.co.uk/itm/Brake-Hose...item5d36a33e8d

It hasn't stopped it happening...
Is this the only hose i need to change?
It did start after i had all 4 discs (rotors) and pads replaced...so the hose seemed a very likely cause.

I read on jeepgarage.org that there had been an FSB from Jeep over calipers on the these...and a replacement part by manufacturer AKEBONO was now recommended.

This is the post on jeepgarage.org...

Re: Help....my brakes are sticking!
You have a 01, so that's got the teeves calaper. They are known to have problems and there is a FSB to replace the front caliper with akebono.

It sounds like you have a "Lazy" caliper, and instead of re-building them I would just upgrade the calipers to Akebono. The stealerships sell them as a kit. Let me know how much they want, and I may be able to get some to you shipped cheaper. I get wholesale prices at my dealership. Since I have 6 Mopars!

Could it be i need to change the caliper?

Cherokee40
You'll have to forgive my ignorance, but i have no idea what or where the parts you mention sit (vacuum booster hose from the manifold to the power brake booster). I suspect the manifold is the master cylinder? And the btrake booster is the servo unit?

Thanks for your help everyone.

bikerneil

Surely an easy way to check if its the hose is to push the brake on hard, release it, try turning the hub [with the wheel off] and then slacken the bleed nipple, this would release any fluid pressure.

claygibson777

I own a 1998 Jeep Grand Cherokee 5.2 4WD Limited. I have just replaced the rear disc brakes (Calipers/pads/rotors turned) as well as the rear parking brakes. I have been scratching my head as I was very careful to do the work properly, following the service manual carefully. The brakes are displaying the same binding issues discussed in this thread.

The information about the hoses and the caliper riding surfaces is something I would never have guessed as they look fine and I found no reference to them in the service manual or in an research online anywhere but here. I'm heading to the auto parts store and then my garage to give your advice a try, thanks, this is a great forum and thus far is the only place I've found the advice about the brake lines.

Frustrated in Florida ...