Brake caliper not releasing

[Dale]

I fitted some new brakes to the ST162 today... they were twin pots off a Caldina ST215 GTT

Got them fitted ok, bled them.. fitted the wheels and I could barely turn the wheels by hand as the pads seemed to be slightly grabbing, I gave them another bleed with the wheels fitted up thinking this could have influenced it, still the same situation.

Took the car for a short drive to see if it was just a bit of crap that needed to wear off (the rotors had a bit of light surface rust on them and the pads weren't new (probably at 50% wear)). It got a little better, but the pads were still rubbing with the pedal released (audibly and you could feel it when the car was going slow).

The rotors are now pretty much shiny like you'd want them to be, but the brakes still aren't releasing fully. If I had mixed up which rotor went with which caliper could it cause one of the pads to drag if they were worn with one of the rotors? Seems unlikely in my mind, I'm a bit puzzled

The brakes were off a low km half cut, <40,000km

Any insight welcome!

[LeeRoy]

Dust in the pad recesses?

Missing, broken, or worn springs?

Cheap or incorectly toleranced/sized pads?

[Dale]

Didn't seem to be any dust in there, factory grease still seemed to be plentiful

Springs were in there fine

And the pads appeared to be toyota ones so I'd assume they're pretty close to spot on!

Basically the calipers and rotors were removed from the hubs of the halfcut and put straight on to my car, I got them as hubs, cv, brakes all still together (one can assume they originally worked fine before the car was chopped in half)

[M.J.H]

Try pushing the pistons back in the caliper and with the car on jack stands run it in gear to check everything else clears first.

[turbo_gze]

Try pushing the pistons back in the caliper and with the car on jack stands run it in gear to check everything else clears first.

A G clamp works good to push the pistons back.

[LeeRoy]

Maybe the piston bores are rusty or lacking lubricant.

I second the use of a G clamp.

[Fish]

SLIDES need greasing/ceased if there a twin piston sliding caliper?

[Hiro]

Are the pads shimmed? Maybe the pads were changed and an extra shim found it's way in there somehow

[Dale]

Good idea Martin, I'll try pushing them back in and see the result

Slides were well lubricated

Nup not shimmed, I'd hope they were original pads and everything in there considering!

turbo gze - a g clamp is an important part of my toolboxes for this very purpose

[oldcorollas]

i believe they are meant to have shims.. the shim kit is very cheap from toyota.

dunno that it should affect the piston pull back tho...

maybe the bores have crud in them? maybe the fluid has water in it and bores have rusted?

the seal kits are also pretty cheap.. might be worth redoing them?

[-GT-]

What condition are your brake lines in? I just replaced mine after chasing an identical problem - one line had degraded to the point it was restricting flow and not allowing the hydraulic pressure to fully release. Did you notice any restriction when bleeding them?

I'd think firstly perhaps pistons aren't sliding freely, but if that's all ok, drop your fluid and blast some air down the lines to see if there's any restriction.

[Dale]

OC - By shims you don't mean the backing plates? They are in there...

Fluid could have quite possibly had moisture in there coming from a half cut (fluid would be fine now... but it would be too late anyway)

If I have no success with any of this I'll get a seal kit and redo them

GT - Brake lines seem to be OK and I had no problems bleeding them, I have no grief with the st165 brakes on the car so I can only assume it's specific to these st215 calipers!

I'll have another look at them over the weekend and check out what's been suggested in this thread

Thanks guys

[Rodger]

My problem in my Ta-22 after puting a new combination on the front:

Discovered that the backing plate combined with the calipers were not mounting parallel onto the rotor. I also had some twist.

There is about 3mm difference between top and bottom (space from bracket to rotor) and around 1-2 degrees of twist. The twist showing up as the pads contacting the outer 10mm on the outside of the rotor and the inner 10mm on the inside of the rotor.

Both mis-alignments caused the pistons to go out of square in the bores and thus not retract.

Perhaps the calipers have some twist induced by a lump or step on the mating surfaces between the caliper and bracket.

Perhaps they are not parallel for a similar reason. Would show up as pads wearing thinner at one end.

Regards

Rodger

[EVOSTi]

pads are retracted from the disc in two ways when you let your foot off the brake. the main way is disc runnout, even a machined disc has enough runnout to push the pads back. the second way is the seal in the piston. the seal deforms slightly when the piston comes out so the seal SLIGHTLY helps pull the piston back in, but its mainly runnout.

so if your brakes are staying applied (btw its normal to have a bit of resistance when you spin the wheel) it could be a few things. most likely thing is your MC is shagged. after you have pushed the pedal the piston in the master cylinder doesnt return fully, possibly spring is worn, seals are swollen etc.

most common way i find peoples brakes are staying applied is because they have put oil in the MC. make sure you havent accidentaly put ATF or some other oil in the MC instead of brake fluid. it happens.

[EVOSTi]

btw its not water in the brake fluid, or no shims etc, but COULD be the caliper slides if they are dirty or bent. unlikely tho if the caliper moves freely.

[Dale]

Small update on this, I had a little time to look at it on the weekend... turns out once the rotor had full pressure on it with the wheel bolted on that it was lightly rubbing against the caliper

Need to do more investigation with my spare hubs to find out what's making it do this

On the plus side the calipers themselves were operating fine