When I took the Zafira for its MOT the other week the guy doing the test said that the front pads would need changing. With the service due soon I went out and bought a set of pads and was set to change them today.
Due to one thing or another I’ve left it a bit late today so decided to check up to see if anyone had changed a Vectra/Ashtray/Zaf B (2006) and posted it on Ewetube, that’s when I started to notice references to master cylinder oil seals and the requirement to “clamp the pipe and release excess fluid through the bleed nipple while pushing back the calliper/cylinder”.
I’ve not had to do this before as I’ve just used the piston tool to SLOWLY push the piston in however, there’s a lot on the web (there always is) about the danger of pushing sludge into the ABS valve and damaging master cylinder seals.
It looks like I need a hose clamp and some tubing. I’ll get a proper one from Carspares (excuse for another river Lea bike ride).
Any comments/knowledge?
I know I've seen this sort of thing in Haynes but I always dread opening up the bleeds in case I end up having to bleed the whole lot so I've never bothered and just pushed the damn things back in, safe in the knowledge that I'm too lazy to keep the reservoir topped up to the max all the time so the fluid doesn't overflow -however- seeing as how a lot of you guys are more "up" on modern cars than I am (I still miss carbs) I thought I'd pass the question on to the forum. What you reckon? Cheers guys
To be safe and not damage the master cylinder it's best to undo the bleed screw and push the piston back with the bleed screw open and lock it just as you get the piston all the way back.
When the pads are fitted undo the bleed screw and do the usual, get someone to press the pedal all the way down and lock the screw when the pedal is down....then pump the pedal until the pedal is solid.
Personally, I've not had this problem on later Vauxhalls, only from the early to late 1990s, but I wouldn't get complacent about it.
You can actually recover the situation by using an old hand fuel pump and pump air out using the pump.....sometimes pumping fluid back towards the master cylinder will recover the situation.
People may be sceptical about this, but I have done this when others have been replacing master cylinders after a pad change.
Cheers guys 
I never bothered with the Senator but I guess the brakes were designed in the 80s.