Brake problem
- Thread starter samp5679
- Start date
Welcome Simon!!
The pistons will be operating on a different part of the caliper, as the new pads and disk thicknesses will push then further in. It might also be that the new pads are tight in the slot in the caliper, but whoever fitted them should have noticed that.
If it doesn't improve within a couple of hundred miles, I think I would consider getting the calipers refurbed. A brake fluid change might help, but I don't really think it would help, unless it is very long overdue.
The pistons will be operating on a different part of the caliper, as the new pads and disk thicknesses will push then further in. It might also be that the new pads are tight in the slot in the caliper, but whoever fitted them should have noticed that.
If it doesn't improve within a couple of hundred miles, I think I would consider getting the calipers refurbed. A brake fluid change might help, but I don't really think it would help, unless it is very long overdue.
I bow to Richard's superior knowlegde of all things 996, let me make that clear. The only things that have been changed are the pads on discs both of which are completely passive. Now the piston, operating deeper into the caliper than it has been is now sliding the "expxosed" section through the square section seal in the caliper and that part of the piston that has been stuck out in the real world may be very slightly corroded, not dangerously so but enough to make it slow to retract, it is purley the distortion of the square seal that pulls the pistons back off the pad, and of course as the pads wear a little bit more of the piston slides through. I am not convinced in my own mind that any manufacturer of motor vehicles would rely on that alone to retract the pedal. It seems to me that something is amiss in either the master cylinder or if there is a helper spring (see how little I know?) it may have become detached or broken. Was the brake fluid changed? I ask becuase the m/cyl never travels full stroke in normal use but when the brakes are bled is goes full stroke and maybe one or two convolutions have broken off the return spring Alternatively we could look at what Richard said and ask OK so supposing the pistons, by not retracting are creating a vacuuum not allowing the fluid to return to the master cylinder, or indeed was a small particle of detritus pushed back into the outlets causing a partial obscuring of the orifices, when the pistons were retracted; or maybe the master cylinder just has too much fluid in it now and the returning fluid is just putting a bit of pressure in the air space. Occams razor look for missing return springs, ovr filled reservoir, but then again if you paid to have this job done take it back to the place where the pads were changed and tell them they messed up if you believe they did.
Hi guys thanks for the information and comments. when I took the car back the mechanic said there was a load of water in the bellows behind the master cylinder, he cleared this out and the brakes were good for 100 mile or so then slowly but surely the problem returned, I think change servo and change fluid, and check for more water ingress needs to be the the next port of call ..... £400 later
Yes, the early 986 and 996s had a problem with water entering the servo and corroding it badly. It seems odd that you didn't have the problem before the pads were changed. In addition to rectifying the servo problem, I think it is probably worth getting them to pop out the caliper pistons, check the bores, and fit repair kits.
Did the mechanic suggest the bellows behind the mastercylinder or servo (there are only bellows behind the servo).
Did he suggest how the water could get there ?
If the bellows are torn / not fitted correctly, water could get in again & could be sucked inside the servo - causing it to return slowly & to internally rust / fail eventually.
If that is the cause the servo needs removing / emptying of water - but the corrosion could well be underway
(Ford Fiestas used to suffer from a similar problem because the drain from the scuttle was directly above the bellows - which were not sealed)
PS Just seen Richard beat to a similar reply !!
Paul
2004 C2 996 40th Anniversary
Did he suggest how the water could get there ?
If the bellows are torn / not fitted correctly, water could get in again & could be sucked inside the servo - causing it to return slowly & to internally rust / fail eventually.
If that is the cause the servo needs removing / emptying of water - but the corrosion could well be underway
(Ford Fiestas used to suffer from a similar problem because the drain from the scuttle was directly above the bellows - which were not sealed)
PS Just seen Richard beat to a similar reply !!
Paul
2004 C2 996 40th Anniversary
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