ST190 front brakes sticking on *fixed*

[rxtoy]

ST190 1993 corona, just a nana 1800 auto.

intermittent fault, it usually happens from cold. get in the car and the pedal feels harder than normal, need more gas to drive forward and it doesn't creep forward like a normal auto. car stops without applying brakes once its warmed up a little. eventually they stick on enough that you can't even drive it, just too much work for the engine.

it seems to be the front brakes, both the front wheels are heating up and you can smell the brakes pretty hard out. not sure if the rears are sticking as well and they're just so crap that they're not noticeable.

as i said above, it doesn't always happen, it is starting to do it more often though. i've just fixed a couple of other problems which i thought were related (wheel bearing and strut top bearing, thought that they might have been causing excessive heat which was causing the brakes to stick) but its still doing it and i'm a bit lost as to what to do next.

any ideas on what the fault might be???? and how i fix it????

i'd drain and replace the brake fluid but i don't see how it could be causing this.

cheers
Matt

[Dell'Orto]

Check the calipers are siezing up, they might need a bit of grease on the slide.

[jondee86]

If it has been a decade or so since the brake fluid was changed, you
probably have a bunch of corrosion happening inside the wheel cylinders.
Rust and crusty crud builds up inside the cylinder until it starts to jam
the piston in the "brakes on" position.

Only fix is to strip the caliper down, clean the piston and cylinder, and
get an overhaul kit with new seals and covers. As above... clean and
regrease the sliders as well.

Cheers.... jondee86

[rxtoy]

i took it in to get the brake fluid flushed today so i could determine whether i needed to rebuild the callipers, the amateurs at AA wouldn't do it because the front brakes were stuck on (happened on the way there).

i waited for it to cool down once i got home, removed both front callipers, determined that they move freely (once the bleed valve is open) and put them both back on. took it for a drive to warm up the brakes and the fronts siezed on again.

this time i jacked up each wheel with the car in neutral and the handbrake off, both the fronts are stuck tight, the rears turn freely.

so i'm pretty sure the problem isn't the callipers. i'm going to try replacing the master cylinder tomorrow and i've got a mate picking up a front proportioning valve from pick a part (unless i can find a new one) so hopefully this will sort it. any other ideas would be great though?????

cheers
Matt

[rxtoy]

master cylinder replaced, everything working fine now.

cheers for the ideas,
Matt