Can anyone offer any advice. I've an 06 Astra H for my sins and I always have problems with the rear pads sticking every Winter time. I've just changed the pads and disc on one side and found the piston wouldn't wind back easily using a proper wind back tool, in fact it was stuck so I applied a little force, that is I put a 6" socket extension bar on the T handle and it worked. I wound it back, finished that side and then stuck my foot on the brake pedal and pumped it, then started the engine and moved the car only to find the pedal spongy and the handbrake is loose and not working on the side I've just replaced.
I whipped the caliper off and got the neighbour to press the pedal (with the engine off) whilst I watched the piston. It came out a little and retracted okay but he couldn't get it to fully extend out. I turned the handbrake arm at the caliper and the piston moved a very little bit out and retracted. I was able to wind the piston right out and then back in again.
Any idea's why the pedal's now spongy and the handbrake not working? I can't understand, I've been doing brake pads for years and years on different cars and never come across this. I'm thinking it's something to do with the auto adjuster maybe?

i would take piston out and adjuster clean and re grease

It sounds like you have corrosion under the piston seal compressing it and causing it to stick to the piston, making the piston is retract too far after the pedal press.
If you wind the piston out manually to meet the pads rather than pumping the piston out you should get an initially better footbrake and handbrake, but you may be masking the root problem.
It may also be possible the seal was dragged by the piston on initial movement and allowed air in, this would also give a spongy pedal.
Also check your replacement pads have no extra locating bumps (the astra pads shape is also used on hyundais and kias), if there is one touching the caliper/piston in the wrong place it will mess up all the adjustment and pedal feel, and cause all sorts of problems.

Dave

I think I'll have to take the piston out then and go from there. Such a PITA
Thanks for the tips, I'll update.

Had the same on my Mrs old corsa VXR,was told it's common.
Banged a refurbished caliper on after freeing it up a couple of times with no joy

On my insignia one of the rear brakes I had to take apart and clean and re grease cos it would stick on slightly even after a thorough clean and re grease it still did it turned out it was a plastic clip on one of the sliders took it off and binned it no probs since

So I hoped this would be sorted by now but no luck unbelievably.
It transpires that the rubber piston boot was split so I removed the caliper and replaced this along with the piston seal. Cleaned it up first and everything moves freely so I stuck it back on and am still having issues.
The pedal is spongy like there's air in the system. I have bled it and put about a litre of brake fluid through in doing so. I have bled it with the engine running as it has ABS and I read this can help. I got it to a point where the pedal was working but still had a little sponginess but the handbrake isn't working on this caliper.
I took the caliper off and wound the piston all the way back and then pumped it up with the pedal before trying the handbrake and it still doesn't work and to add insult to injury, the pedal just travels all the way to the floor now as though there's trapped air.
I can see that the handbrake quadrant is moving when the cable pulls it and it's pulling it through it's whole travel as per the opposite side that works fine.
I'm stumped now as to why it doesn't work. My last thought is that maybe the piston adjustment mechanism is stuck therefore not allowing the piston to come all the way out but it's lashing down outside and I'm already damp, smelly and trying to warm up (and fed up).
Any thoughts why one caliper wouldn't work?

Have you got something to clamp the flexible hose going to the caliper? (I'm assuming you have cord reinforced flexible hoses, if you have wire reinforced (not normally with vauxhall) or ptfe hoses this step will not be possible)
Clamp off the hose, then check the pedal to see if it has firmed up - if it does there is still air in the caliper - if it has no effect there may be a fault or trapped air elsewhere.

To bleed your caliper and reset your handbrake do the following:
Wind the piston fully in and then back out until there is less than 1mm clearance to the pads. This should reset the handbrake caliper mechanism. Do not use the footbrake to move out the piston as the handbrake mechanism will not reset.
Use your caliper windback tool to hold the piston in position, then move the caliper so the bleed nipple is at the highest possible point. (IIRC this will be about 45° from normal fitted position)
Give the caliper a couple taps to bring any air to the top and bleed until there is no visible air in the fluid.
Refit the caliper and pump out the brake pedal, then operate the handbrake - both should now be correct.

Dave

Thanks. The hose is very stiff walled and doesn't feel like it would compress without physically splitting. It's not like other cars I've successfully clamped.
As it happens I've just been out and removed the whole caliper and piston again. The mechanism in the back of the piston is seized solid. It won't turn or even come out of the piston and I guess it should do to allow the piston out properly. I've left it soaking and I'll try tomorrow.
Thanks for your reply I'll bear it in mind when I put it back together tomorrow if she'll let me!

So, to close this thread and thank all for the advice.
I normally wind the piston right in and then pump it out with the pedal when everything is refit but this time I screwed it in and then out to within 1mm of the pad as suggested and then it turns out, apparently, that with a car with ABS you have to use a pressure bleeding kit to overcome the valves in the ABS unit, something I wasn't aware of and I don't really like my Eezibleed as it's emptied itself all over, under pressure and put me off. Well it did the same today however, it seems to have sorted everything.
Thanks again for the advice, even just to talk it out because it was stressing me to heck and I didn't sleep much last night

Good to hear you sorted it and get a good night's sleep tonight

It was like this the night before SVA