OK I have read alot of the posts and think I have the answer or well on the way but,....

 

After 4 days of heavy rain and not using the car I attempted to do a 25 mile journey and halfway had to stop as something was not right, it trned out the OSF wheel was well hot , too hot to touch and the front wheel when jacked up was hard to turn, brake caliper sticking right! Well after 139K  the week before the car passed the mot but i had a low front pad advisory so bought some new disks and pads , i just attempted to do the job but it started raining hard and I had to reassemble the old parts I could not quite get the outside pad in propelry it appered to be a very tight fit, even the old pad was a bitch to get in and was seized in that position , I cleaned up the sliders and they looked smooth , the carrier was tight and the piston moved back but not quite enough to get the new pads on the old disk, so i probbaly needed a few more mm of piston movement .

 

I guess when i do the NSF I will answer my own question but should the outside pad be a smooth fit in the slider or does it just sit there tight , I have experience with MTB , motorbike brakes and expect its the former. If so any ideas why the problem has arose , I admit to not doing any brake maintenance in the past but why should the carrier suddenly change shape, could it be it warped slightly from the heat , the sliders were removed from the carrier and the carrier cleaned with a wire brush removing some surface rust but it still looks useable , mmm confused!!!!

 

 

Thanks guys , great forum and appreciate any advice ......I changed the rear disks at about 110k and they appear fine.

 Did you work the piston a few times to ensure that it is free, should there be anything on the piston surface under the boot it can get transferred back into the caliper bore causing stiction. Just be sure that when working a piston you do not force it out too far. There is also the chance that the flexible hose could have collapsed inside.

I will try that at the weekend but brakes function fine even with the pads that are resembling a burnt paperbacked book! It took quite alot of force to work the piston back with a tire lever but it started chucking it down by this time and working on the side of the road is not great even in good weather.

 

Main issue is the outside pad has to be forced into the carrier and does not move freely , the inside pad is a tight fit but moves on the slider. My bike brakes are a loose fit by comparison. If its a dry weekend I will have a go at the NSF and see what that side is like. I'm thinking that maybe the OSF carrier has been twisted slightly as I drove 13 miles b4 i stopped to check what the noise was .......stupid i know.  Knowledge is power and I should have cleaned / serviced the calipers b4 now , my bad!

 

The car is verging on 140K of trouble free miles so she deserves some tlc!

Try popping the hose off the brake servo and see if it releases. The none return valve in the pipe can be known to fail. 

14 hours ago, cello said:

OK I have read alot of the posts and think I have the answer or well on the way but,....

 

After 4 days of heavy rain and not using the car I attempted to do a 25 mile journey and halfway had to stop as something was not right, it trned out the OSF wheel was well hot , too hot to touch and the front wheel when jacked up was hard to turn, brake caliper sticking right! Well after 139K  the week before the car passed the mot but i had a low front pad advisory so bought some new disks and pads , i just attempted to do the job but it started raining hard and I had to reassemble the old parts I could not quite get the outside pad in propelry it appered to be a very tight fit, even the old pad was a bitch to get in and was seized in that position , I cleaned up the sliders and they looked smooth , the carrier was tight and the piston moved back but not quite enough to get the new pads on the old disk, so i probbaly needed a few more mm of piston movement .

 

I guess when i do the NSF I will answer my own question but should the outside pad be a smooth fit in the slider or does it just sit there tight , I have experience with MTB , motorbike brakes and expect its the former. If so any ideas why the problem has arose , I admit to not doing any brake maintenance in the past but why should the carrier suddenly change shape, could it be it warped slightly from the heat , the sliders were removed from the carrier and the carrier cleaned with a wire brush removing some surface rust but it still looks useable , mmm confused!!!!

 

 

Thanks guys , great forum and appreciate any advice ......I changed the rear disks at about 110k and they appear fine.

 

Did you unscrew the brake reservoir cap? Otherwise it reads like a sticking piston.

I had the same problems with ECP dogsh!t pads, ended up tickling the metal backing plates with a grinder until they moved freely.

Terrible problem on the Octavia's.....

I do think once you have completed the job and bled the brakes you will find that all will be ok (taking into account all the above suggestions of course, ie 'working' the piston a few times carefully though, and removing reservoir cap.

I doubt you have warped anything

Just a good clean off of everything and possibly a bit of filing, refit using Ceratec grease rather than copper grease, especially on the rubbers, bleed them and you should be fine...

A G clamp is your friend for pushing piston back in...

Agreed with using a g-clamp if you haven't got a piston winding tool. They aren't expensive anymore for a kit that is decent enough to use once or twice a year. You should get a better push on the piston than you can with a tyre lever and providing there is no rust on the piston, it should go right back with no trouble.

 

Another unfortunate consequence of having the brake overheat is that the piston can warp. This can be quite difficult to diagnose until the brakes get warm again sometimes. While this is more common with the bacolite (hard plastic) pistons some manufacturers use but I have seen it happen to metal pistons too.

 

As you suspect @cello, the pads should be a snug fit but be able to move freely. The old pads that you had to put back in may well have swelled up a bit with rust and there might still have been a bit on the carrier where the pads sit. Don't be afraid to crack the carrier bolts, remove the carrier and get a wire brush and even a file or a little zip wheel in the end of a battery drill into those pad seats to get them nice and clean. Then get a nice layer of grease on the pad seat. Hopefully you'll find things go a lot more smoothly. 

Finally completed the job , had to use the old disks to push back the piston with a long screwdriver and just had the room to install the pads with the new disk. Also filed the pad ends slightly to get them to slide in snugly. 

 

So far so good , first long drive is tomorrow but a 5 mile test drive was ok. Hard to think those carriers take the full load of the car braking from xxx mph, not sure what they are made out of but they seemed to quite badly corroded so guess its mild steel, all that stress  divide by 4 , wow!!!

 

 

@cello If you haven't 'worked' the pistons a little it is likely to seize again in the near future............ You may be lucky tho.

I moved them in a couple of times but think the pads were the reason for the sticking caliper , rust and other shi* had built up in the channel they slide in and caused them to bind against the disk. The NSF was not as bad as the OSF and tapping the caliper with the handle of a hammer allowed them to free off for the slow drive home.

 

So far so good today with the brakes , backup to high 50's with the mpg without trying too hard. Still have the NSF steering rod to change where the ball joint has some play. Then only the cam belt to do , which is well overdue which I have stupidly put off for far too long , think its at the 70K mark and five years since it was last done......yes I know :(

Can anyone recommend the best method to remove a sheared off disk screw? I tried a pair of molegrips but they just slipped on the remaining screw thread, i know you can buy bolt extractors but its such a small diameter not sure i would be able to use them mmmmmmmmm

https://www.amazon.co.uk/Reverse-Action-Twist-Drill-Bit/dp/B075R6GCDM 

 

These might do it.

The screw doesn't really matter, it's for convenience essentially, the wheel is what clamps the disc in place. 

On 29/10/2020 at 00:15, cello said:

Can anyone recommend the best method to remove a sheared off disk screw? I tried a pair of molegrips but they just slipped on the remaining screw thread, i know you can buy bolt extractors but its such a small diameter not sure i would be able to use them mmmmmmmmm

 

Plusgas followed by file two flats and use an adjustable spanner?

Thats a great idea, why I never thought of it , thanks buddy!