Hi all

2019 Fiesta ST Line and time to dismantle and clean the brakes, starting at the rear.  Cleaned everything, retracted the piston OK and then had a bit of difficulty lining up the slider bolts.  Eventually overcame that but then found that the disc would rotate freely until the final couple of turns on the slider bolts after which it refused to budge. With the wheel back on, it reluctantly turned.  Nevertheless gave it a very short run after which the disc was at 100C+ compared with 35 opposite wheel.  The spring on the inner pad seems to contribute as it's difficult to get the caliper lined up to insert the bolts.  I'm stymied on this:  any suggestions appreciated.

Thanks

Based on my understanding (which probably isn't) the only things I see is that a) it's the inner pad  -  is this next to the piston? AND b) the difficulty of reassembly.
I'd check that the piston is really fully back and the pad is fully bedded into the piston (if, as I imagine the spring clip locates inside the piston)you mention.
The reason for the difficulty with the bolts really needs thorough investigation as it shouldn't happen - compare with other successful side?

Photos?

53 minutes ago, Freddy42 said:

Cleaned everything, retracted the piston OK and then had a bit of difficulty lining up the slider bolts.  Eventually overcame that but then found that the disc would rotate freely until the final couple of turns on the slider bolts after which it refused to budge.

Incorrectly assembled, and potentially dangerous.

Something has not been put back as it should be. By what means did you retract the piston ?

The piston was retracted with the correct tool for the job and is well clear.

The spring mentioned doesn't clip into the piston, it is at the rear of the pad and fits into the caliper, so when relocating the caliper, it's pushing against the spring.

Unofix:  I've done this many times on previous Fords and the current Focus and never had a problem.  This is the first attempt on the Fiesta.

9 minutes ago, Freddy42 said:

I've done this many times on previous Fords and the current Focus and never had a problem.  This is the first attempt on the Fiesta.

So have I, but not on the Fiesta ST Line, although I'd expect them to be the same. I can't understand why you had an issue with the slide pins. Has one of them become damaged ?

No damage

I am trying to work out what you might've done wrong. Any chance you can take some photos of how things are looking?

Not sure if these will help.

Just to reiterate:  The piston is retracted and the caliper slips easily over the pads with room to spare.  The lower of the slider bolts is started first and the spring pushes the upper one out so some pressure required to locate the upper bolt.  The disc moves freely until the last couple of turns on the bolts when it seizes solid.  Just starting now to have another look.

Edit - ignore.  Was thinking carrier bolts not slider bolts.

What's that stuck to the front of the caliper?  Some sort of pad retainer or anti-rattle clip?  Get rid of that and see if it works freely without.

Also (may be totally wrong) but that piston doesn't look all the way back to me so needs checking as, from the description, it seems to be a possible cause?

32 minutes ago, TomsFocus said:

Edit - ignore.  Was thinking carrier bolts not slider bolts.

What's that stuck to the front of the caliper?  Some sort of pad retainer or anti-rattle clip?  Get rid of that and see if it works freely without.

Tom     If you look at the parts diagram from Unofix, you will see that one of the pads has a spring attached.

Just reassembled for the umpteenth time and the wheel could be turned by hand as normal  After a short run, It's still running hot, 75, although not as hot as yesterday.   Jacked the car up and there is now resistance to turning the wheel by hand which suggests that the piston is not retracting after brake application.  Does that sound likely and what's the remedy.

3 hours ago, Freddy42 said:

Does that sound likely and what's the remedy.

That dose happen, especially on rear brake callipers. The usual answer is to fit a new calliper.

Just a thought, this is not an issue with the handbrake is it ?

I was thinking the same re the piston. Use a brake hose clamp, then loosen the bleed nipple then retract the piston all the way so it's flush with the cylinder. (apologies if I'm telling you how to suck eggs, etc)

6 minutes ago, Freddy42 said:

Tom     If you look at the parts diagram from Unofix, you will see that one of the pads has a spring attached.

Just reassembled for the umpteenth time and the wheel could be turned by hand as normal  After a short run, It's still running hot, 75, although not as hot as yesterday.   Jacked the car up and there is now resistance to turning the wheel by hand which suggests that the piston is not retracting after brake application.  Does that sound likely and what's the remedy.

Yes, I can see that spring.  But it looked like there's something stuck to the front face of the caliper as well, not shown on the parts diagram, unless that's just a trick of the light on the picture?

The piston gets retracted by the tension of the O-ring around it.  If it's not retracting then it needs a rebuild with new seals.  Or just fit a new caliper.  Worth noting it won't retract very far back due to the handbrake mechanism acting on it.  You could leave the handbrake disconnected and press the pedal a couple of times to see if it retracts properly without any handbrake use.

Unofix & nicam49

Activities have come to a halt for lunch and to regain composure.  I'll investigate your suggestions shortly.

Thanks

I've not worked on that exact caliper before, but it strikes me as odd that only one pad appears to have a spring on it. When springs form part of the pad (which it looks like is the case here) I would expect to see both pads having them and yet only one of yours does. I don't know why that would necessarily cause the issue you've described (even without it retracting itself the disc should push the pad out of the way), but it's all I can see that's odd from the photos.

Have you dismantled the other side? How does that compare?

1 hour ago, MJNewton said:

I've not worked on that exact caliper before, but it strikes me as odd that only one pad appears to have a spring on it. When springs form part of the pad (which it looks like is the case here) I would expect to see both pads having them and yet only one of yours does. I don't know why that would necessarily cause the issue you've described (even without it retracting itself the disc should push the pad out of the way), but it's all I can see that's odd from the photos.

Have you dismantled the other side? How does that compare?

It's the inner pad only that has a spring - there is not a recess in the caliper to accommodate a spring on the outer pad.

The way my luck is, I daren't dismantle the other side!

Tom, you say 'The piston gets retracted by the tension of the O-ring around it. If it's not retracting then it needs a rebuild with new seals.'  I've just operated the brake pedal a few times to see what the piston does, and it does not retract at all.  It looks as though a new caliper is now on the to-do list .   Seems a bit soon at 21000 miles.

16 minutes ago, Freddy42 said:

It's the inner pad only that has a spring - there is not a recess in the caliper to accommodate a spring on the outer pad.

Type your reg into a online parts supplier and see what pad kits they have listed for your car.

Quote

Tom, you say 'The piston gets retracted by the tension of the O-ring around it. If it's not retracting then it needs a rebuild with new seals.'  I've just operated the brake pedal a few times to see what the piston does, and it does not retract at all.  It looks as though a new caliper is now on the to-do list .   Seems a bit soon at 21000 miles.

The retraction is tiny - fractions of a mm - and so you won't see it by eye.

Yeah, as MJNewton says. When you retract the piston, DON'T force it back without, a) clamping the hose, and, b) loosening the bleed nipple. You don't want the fluid forced back into the master cylinder as it flips the seals in the MC and causes much grief. Rear calipers you have to wind the piston in, as well as pushing it in. 

If there's a rubber sleeve on one of the slider pins, then DON'T lube with normal grease, use synthetic, like silicon, else the normal grease reacts with the rubber and makes it sticky and expands, then pin jams in the caliper. If you need to, you can get caliper rebuild kits from Bigg Red

https://www.biggred.co.uk/

Reassembled yet again and for reasons unknown, now back to normal.  Thanks for the responses and humble apologies for wasting your time.