Putting new front brake pads in - girling

[CovKid]

I think I'd have gently worked the pistons in and out at least a few times with a cramp or something similar to stop them actually coming out the bores before jumping straight to replacing the master cylinder. They may just be sticking. If that proves fruitless then look further but it costs nowt to do a check like that.

[California Dreamin]

I'd be a little cautious about wrighting off the master cylinder so quickly....new pads on worn disc's (complete with lip) I would have been inclined to take the lip off with a file and properly clean and lube the sliding pins/pad edges and contact areas (piston and opposite fingers)
This could be dry or even bent sliding pins, tight pads in the carrier?

I'm with Covkid and think that you need to eliminate all other possibilities first.

Martin

[AdrianC]

This could be dry or even bent sliding pins, tight pads in the carrier?

Apart from the result of cracking one bleed nipple open - fluid came out under pressure, and both discs were free to rotate. That, surely, rules out anything but hydraulic pressure being held on.

[California Dreamin]

I agree but why would it be any different on the worn pads compared to the new ones? it's not clear cut, that's all I'm saying.

Martin

[CovKid]

And the fact that checking for any fouling is a darned sight cheaper and less hassle than taking out the master cylinder which lets face it, is a major operation. You could do that and still have the problem. Rule out the simpler stuff first.

[chuckle-bus-tom]

The calliper pistons move quite freely with the old pads in, and braking is fine. The nearside calliper is newer (2007) but it had the same problem with the new pads.

Once I had the pistons all the way in using the wood and the clamp the new pads went in no problem, but there was barely a centimetre of movement available for the piston.

I've held fire with getting a new master, while I get everything stripped down and see what the fuss is about.

[CovKid]

With new pads, the pistons have to be virtually fully in as pads that much thicker. If the discs now turn without too much rubbing and the pads retract enough to avoid that, then job is done. Its not actually that unusual to experience minor rubbing with brand new pads. They do take time to settle in I find. Ofcourse, worn discs will also affect that - again until pads have bedded in. Clearly they don't want to be locked solid and it may require working those calipers in and out a few times to get a nice smooth action. Lets face it, the pistons haven't been in that far for some time.

Either way, you don't want the hassle of a master cylinder swap if its simply not needed - thats what fitters do. Mechanics will always check the chain of events and go from there. A dying breed sadly.

[California Dreamin]

On rare occasions I've had NEW brake pads that have been too thick, as in: the friction lining has been too wide. In those circumstances I have had to use a piece of COURSE emery cloth, laid it on a flat surface and literally take off a millimetre of lining until the pads fit without force and free piston movement is available.
Not strictly 'by the book' but a perfectly acceptable work around.

Martin

[CovKid]

And less barbaric than an angle grinder He's right though. I've had to that once in 27 years.

[chuckle-bus-tom]

Is it OK to use plus gas on the pistons to help them free up? Logic tells me no, but thoughts I'd ask!

[sglcc]

Hi Chuckle-bus-tom - did you ever get to the bottom of your sticking brake pad problem ?

[SILVERFOX2013]

iv had this problem caliper piston not retracting what i did was let them move out then using a green scotch bright pad rub the grime mark/ring off
it seams to work not saying this is the way but has worked for me on other cars as well

[chuckle-bus-tom]

Hi Chuckle-bus-tom - did you ever get to the bottom of your sticking brake pad problem ?

I got to the bottom of the problem, which was the calliper sticking due to grime build up and (probably) the low amount of use the van gets. So I did this:

iv had this problem caliper piston not retracting what i did was let them move out then using a green scotch bright pad rub the grime mark/ring off
it seams to work not saying this is the way but has worked for me on other cars as well

[SILVERFOX2013]

Hi Chuckle-bus-tom - did you ever get to the bottom of your sticking brake pad problem ?

I got to the bottom of the problem, which was the calliper sticking due to grime build up and (probably) the low amount of use the van gets. So I did this:

iv had this problem caliper piston not retracting what i did was let them move out then using a green scotch bright pad rub the grime mark/ring off
it seams to work not saying this is the way but has worked for me on other cars as well

happy it worked for you as it has me