Cosmo

took the 3dr for its MOT today, 1st try at it after finishing it off.

Failed on a few scatty things, fog light bulb and headlight alignment, no worries.

But the tester noticed that all the brakes seem to bind on after the pedal is released, not just one but all the calipers (and i've not long chaged the fronts so am not expecting sticky callipers, especially not all 4!!)

Is there somer sort of 2 way release valve or something on the system that shoiuld relax off after your foot comes off the pedal, somehow all the brakes are sticking just a touch on - i can just about rotate the wheel by hand.
To be honest you can feel it as you drive, when pulling away from junctrions you can feel the resistence and when you come off the throttel you can feel the car slowing as if the brakes were on a touch (well i suppose they are)

Anyone had this problem? Anyone know how to fix it??

Thanks!!!!

Cosmo

Oh and also the brake pedal is quite hard, not as hard as when the ABS pump stops working the ABS pump kicks in and out as it should the fluid level in it does look to be a little (1/4") higher than it was after i'd finished bleeding the brakes on the car too but i could be just imagining that.
They are definately a bit harder than normal though if you catch my drift, its effectiveness is very high up on the pedals travel. The brake efficiency passed the MOT no probs though so they're all working fine, just sticking on a tad and not releasing fully???

tabetha

New pads can sometimes do this, but within a few miles have knocked off the high spots.
Were all pads/discs calipers new ?
tabetha

Cosmo

Calipers were bought off here, off a car that was in use prior to me haing them though. Pads were new yes.

Rear calipers were original items with original pads (still lot of life in them)
Handbrake on rears functions properly too.

The wheels do turn by hand, just not freely, it seems very strange. Over night i have noticed that the fronts do stick quite bad, sometimes the rear wheels spin on my drive (stone chippings driveway) before they break free.

When i got the car before the resto i noticed the owner had undone the brake lines to the front caliers and bled the fluid out to free the brakes. seeing this i figured the calipers were stuck fast so bought replacements, but now my replacements are sticking on, i find it real bad luck if this second set is stuck fast too, it must be something else surely? especailly with the back brakes having the same problem? The back brake pistons move in an out with the handbrake suggesting they're not seized but just dont release enough (not only with handbrake also foot brake), same as the fronts, they've all passed the brake test showing they move in and out, just not far enough in again to allow free movement.

not knowing much about the braking system could it be the valve block etc? But then again why would it get worse overnight, that would suggest caliper at fault, but all 4? Even after changing the fronts, that would mean 6 out of 6 calipers i've tried are all sticky, that would be bad luck!

I'm not even sure if he's correct about the rear wheels as they have more resistance (dont spin freely) due to going through the diff and dont spin freely anyway?

Its the last thing stopping me getting my MOT after all this time, and i've only got a week to sort it before i get charged another £55 for a test

LHD220Turbo

iTrader: (4)

i'm not brake expert; but maybe try re-bleeding them

how did you bleep the last time?

should be

1) rear N/S
2) rear O/S
3) front N/S
4) front O/S

Cosmo

Bled them just as you've described, furthest away first. They bled out real well. They function great, did realy well on the brake test on the MOT, just didnt back off enough to let the weels spin freely when off the deck?

tabetha

The rears are certainly not going to spin freely, as both wheels spin together with LSD being fitted.
With the added info it does certainly sound as though there is a lack of correct release of pressure.
The abs block doesn't come into operation unless it senses a fault, so that won't be doing it, try pulling on the brake pedal, maybe this is tight and binding.
I would also take off the reservoir, and check the holes in it where the brake fluid is drawn into the master cylinder, are totally uncovered, if the pistons are sticky this will cause it, or if they don't return all the way due to a broken spring etc, this will keep the system pressurised.
tabetha

Cosmo

Update from what i've done today:

WEnt out to the car, didnt put ignition on , jacked it up and tried the front wheel, itr span fairly loose (not completely though) I then put ignition on and pressed brake pedal once, front brake went solid, even with pedal up!

So i descided to try and de-pressurise the system, i opened the bleed valves on the caliper, turned ingintion off and allowed pressure to drop. Still the caliper was solid, i then tried pumping the pedal with valves open to really de-pressurise it, fluid folwed out and still the caliper was stuck fast.

this screams siezed calliper i'm guessing? Was my trial a sound one? Would i have de-pressurised the calliper?

I just cant understand why it was free when i first went to it?? If it was siezed why hadnt it stayed locked on from my attempts yesterday??

Help please!!!

tabetha

Yes it has got to be the caliper stuck, as you have removed the fluid actuation by bleeding and leaving open.
I would take the pads out and put a thin 1/8th" bit of wood in each slot where the pads go, and pump the pistons till they touch the wood, they won't come out, with disc and wood in place, now carefully peel back the dust seal, and spray with wd40, then work in out a few times, this will free them.
When you take it back on the road roast the brakes, as this helps free them too.
You certainly have been unlucky with sticky calipers!!
tabetha

Cosmo

Thats a job for the weekend then, i had a set of old calipers in my garage never played with calipers before so i tried to remove the pistons to see how hard it was this aftgernoon, managed to get 2 out using mole grips and spinning the piston, the 2 others wouldnt budge! After 2 hrs i gave up, was dreading doing that to the calipers on the car (especially as i've got to do all 4!!)

Your method of putting a small packer and running the pistons out sounds a good one to me! Just one question, once they are fully out and still on the car how do you get them to go back in? I usually have the caliper off and use a G-clamp to push pisons back in, but i wont be able to with the caliper still in place? Plus i'm expecting the first few goes to be stiff as they're having the problem going back in.

Is it worth taking he caliper off and pumping the pistons in and out to make it easier to push in with my G-clamp method, or do i definately need them on the car still?

Thanks for your help!

tabetha

Keeping them on the car allows for you to use easy to use pedal to pump them out, when they have contacted the wood bits, you simply pull out the bits of wood, this leaves space then to get a lever in there to lever back in, try to do it as squarely as you can, even from the inner edge as well next to the bell of the disc.
I ended up having to scrap 2 pistons when I did mine as they would not budge, even though I had a dedicated amplifier pump on them at 2600 psi.
Ended up machining out to as thin as could get and bodging out.
I even used a cast rod and welded metal to them but still no budge.
I would seriously consider getting new/recon ones as they are £55 or so each, last time I got a set for someone, this is exchange for which you could put in the most knackered set.
The caliper pistons should retract inwards around 1mm when the fluid pressure is released, as they intentionally have square cut seals to make this happen, you can see this, if you can't they are not retracting.
tabetha