Problem after Brembo caliper rebuild?

[rumpelstiltskin]

I've rebuilt dozens of Brembo calipers on motorbibkes i've had so i'm used to the process.This is the first set of Brembo calipers i've rebuilt from a car (Fiat 20v turbo)and i've run into problems.Pistons were in good nick,cleaned them up,replaced both seals on each of the four pots.I've put them back on the car but after a short run around the streets i could smell hot pads!!!Got home and both of the front discs were hot!!
I took off the caliper from the disc but still had it plumbed in,got my better half to press the brake slightly a few times and observed the pistons,they all moved and just settled back nicely aftr moving,i don't get this,what have a done wrong,it's as if the pads aren't letting go the discs after braking.You can turn the wheel when front of car is in the air,slightly stiff to move but not overly so.Anyone any ideas??

[rumpelstiltskin]

TallPaul said:

Pattern pads that are fractionally oversized & binding in the caliper?

Interesting you should mention that,had to file them to fit!,they are sliding back and forward fine in the caliper.

[rumpelstiltskin]

stevieturbo said:

Lots of alloy bodied calipers have stainless platforms where the pads slide into.

Unfortunately underneath these corrode and they make that space smaller, and pads often dont fit properly.

And can be worse again as above where pattern pads are often the wrong size too

The corrosion seems worse on calipers where owners go nuts with alloy wheel cleaner. Usually the dirtier they are, the less corrosion there is.

Yes it has these platform,held in place by those,"Go on,try and unscrew me and i'll snap off!"screws.One was particularly high but i managed to pound it flat,plus soaking underneath with wd40 to force out dirt.I took the easy option and filed the pads!Discs just seem to be getting 'too' hot though i think.

[rumpelstiltskin]

Mr2Mike said:

The Coupe is a fairly weighty car and the brakes will get pretty hot if you are using them a lot. You don't have to try very hard to fade them, especially if you are using cheap pattern pads.

If you aren't driving it hard and the pads are genuinely overheating then they must be binding. I owned a 20VT for a long time and filing the pads down is a bodge that doesn't last with these calipers. Any corrosion already present just gets worse.

Was this problem present before you rebuilt the calipers, or did it only happen afterwards?

Brakes were ok before i done the caliper.It feels brakes are dragging although as i said with the front wheels in th air i can turn the wheels 'fairly' easily,they aren't jammed solid or anything.Pads are Mintex incidentally which came with the vented,drilled and grooved discs.I've driven a car with pads jammed against discs before and the pads reeked to high heaven.The discs are getting hot but not much smell of pads now.

[rumpelstiltskin]

After much fretting and with the brakes still dragging i decided to replace every rigid brake pipe,and the flexi right back to the abs unit.Just incase anything freaky was happening within the flexi.After i bled the brakes the disc turned freely within the caliper for the first time since i rebuilt caliper!,great i thought.Stuck the wheel back on,turned wheel by hand and it dragged again??There is no play in the wheel bearing and wishbones/balljoints etc are fine.

[rumpelstiltskin]

kev b said:

I had this problem on a Discovery, the discs were machined incorrectly but they were cheap discs.

I have also seen motorbike rear brakes binding badly because the reservoir was overfilled, there is no air vent in a motorbike reservoir and the pistons are pushed out when the fluid becomes hot and expands.

The first thing I would do is refit the old pads and see what happens, it's a quick and free check. I won't insult you by asking if the seal grooves are free of corrosion and the pistons spotless.

I've rebuilt Brembos on bikes many times and never had any issues,yes everything was spotless,seal recesses etc.I'll try all other suggestions though,thanks!