Self braking brakes? Are they the future?..........

...........I bloody hope they ain't!!
:o

Having a bit of an odd problem at the moment with my Nova GSi using Calibra turbo front calipers and 285mm discs, the background:

The pads needed changing a few weeks back so I went to GM dealer and got a set of std GM pads for a early (92-96) Calibra turbo, drivers side caliper came off and the compressed as per normal, new pads fitted, passenger side caliper came off but the piston was seized so I removed the caliper from the car completely, put the caliper in a bench vice and removed the piston - it had a small patch on it where it was pitted and a bit crappy so I cleaned it up with some worn emery cloth, refitted it with the dustcap (Checked for splits - OK) and it slid in and out as it should - fitted caliper and pads back on Nova.
Obvisouly the brakes now needed bleeding due to the caliper being totally removed from the car and I thought that whilst I was at it I'd change the fluid as I've no idea how long it'd been used (Not changed it in the 3 years I've owned the car), so open bleed nipple on drivers side caliper and remove flexihose from passenger side (Bleed nipple had broken off years ago), pumped all the fluid out, closed nipple and refitted hose, filled with new Dot4 fluid.
Bleed the brakes as per normal but had to bleed the passenger side front at the hose because of broken nipple - couldn't get anywhere near a decent pedal, thinking maybe a airlock in the master cylinder we bled all 4 union joints at the master cylinder - still no pedal - we put it down to the broken bleed nipple.
So we extract the broken nipple and replace it with a new one, and I remove the drivers side caliper to check the piston, the piston is fine but the dust cap has a small split in it - I get a new one from GM and refit them back to the car - rebleed the brakes once again - still no better.
Thinking that it may now be knackered seals in the master cylinder from where I pumped the old fluid out (Maybe pushing it past the seals) I get a brand new one, fit it, use new fluid once again and bleed all four corners and from the master cylinder yet again!!
Pedal is now better but still not great (at least 3/4 down before it starts to work) and all the air is out of the system, so as a temp measure I adjust the brake pedal as much as possible to give myself a bit more bite and feel - and it works a bit better, the only problem being that after a while the brakes will begin to bind, so I release the pedal back to where it was.

Now the situation I have is that when the car has been stood for a few hours the brake pedal will be back to it's rubbish self (3/4 down before it works) but after 10 mins of driving they'll begin to bind regardless of how often you use the brake pedal - I live near a duel carrageway which I have to use for work 15 miles away, I can get onto the duel without having to use the brakes much and 10 mins along the carriageway I can feel the brakes beginning to bind and it'll slowly get worse - upto the point of getting to work and the brakes smoking!!

Now obvisouly this is far from ideal because correctly working brakes are kind of important to me as they would be anyone else!!
The only thing I can think of is maybe one or both of the flexihoses have broken down inside and aren't letting the fluid flow back as easily - the only problem there though is that it doesn't need braking to make it bind - it seems to do it by itself.
It's almost as if the servo is slowly applijng pressure to the master cylinder and that's causing the brakes to bind more and more as time goes on.
I had though maybe the servo was knackered but I've been assured that when they go the pedal goes rockhard and you have almost no brakes at all - and that's not the case here.

Anyone got any ideas for me to try?

Cheers for reading this yarn!!

Jules

Don't want to create any hard feelings but.........it is possible to have the calipers on the wrong sides and have the nipples at the bottom.....wrong, air rises and brakes won't bleed.

If this is so then the combination of having air in the top of the calipers and some warmth from the disc, pads, wheels, hub, car etc. will cause the air to expand and apply the brakes slightly.

Just my 2pence worth.........or it's a small fairytale creature squeezing the pipes or something.

I will check that but the thing is because I done one side at a time it's not possible for me to put them back on the wrong way round!!
I'm 99% sure that the bleed nipples are at the top though although I will check just to make sure.
You theory sounds right though - it tends to be worse on hotter days so maybe there is something in it after all.

Cheers

i had an ate caliper do this , it just required rebuilding
it was full if crap and the piston was sticking

Also the part that most people are unaware of or just don't bother is the sliders that the caliper sits on, these would also benefit from a strip down and greasing.

I had to do mine, as the brakes were stuck on cos the caliper wouldn't slide back and forth on the slider so one pad rubbed and smoked and stank bad.

Oh yeah I forgot to mention those - they were sticky but I greased them up the last time and it still plays up.
That's why I'm a bit confused by it all - all the bases seem covered and it still does it - I think new flexi hoses are the next thing to replace.

Cheers

Jules

Just been out to have a look at the car and it seems the bleed nipples are at the bottom - strange because that's the way they've always been, perhaps that's why it chewed through the last set of pads!!!
:lol: :oops:

I'll swap them round over the weekend and see what happens.

I did that when I put my ATE calipers on my old car, but fortunately seem it before the second one was bolted down.

And that will (hopefully) be the answer to your problem :wink:, you have a large air bubble in the caliper.

Swap em over and let us know.

Will do - cheers Robb - I always thought that my V6's weren't as good as my old 16v stuff - maybe now I know why!!!
rofl!!
:lol: