Technical Brake Failure

[g8rpi]

So I was turning the car (1.9 mJTD 16V manual) around when I got home from work and after I'd reversed there was a grinding from the off-sie rear. A quick look before going in for my tea it seemed the lining was worn away. This seemed strange as there was plenty the last time I checked. A closer look showed that the lining has detached from the steel backing plate. Obviously can't be driven at all as the loose pad could lock the wheel up without warning. No stock locally so have ordered a set of pads and disks online, they should be here Tuesday. Good news is they were on clearance so only £47.13 for the lot. So a little job on Tuesday afternoon.

 

[s130]

Pad lining material separating from the pad backing plate must be a very rare occurrence indeed (on any brake pad/vehicle) and something I've never come across.

Enjoy your Tuesday afternoon

 

[varesecrazy]

Pad lining material separating from the pad backing plate must be a very rare occurrence indeed (on any brake pad/vehicle) and something I've never come across.

Enjoy your Tuesday afternoon

Seen it a few times.

Friend had it last week on an S.max

Often occurrs on seldom used vehicles.. or pressure washed ones.

The steel pad mount area corrodes.. these blisters prise the friction pad beyond the
Grip of its adhesive.

Often results in a locked wheel..!!

Locked front wheel at 60mph.. on a bravo.

Seen shoes do the same.. the loose lining will climb over the good one.. giving a very effective brake

 

[g8rpi]

So I got a set of pads and disks on clearance from an ebay seller for £47 and the good news is they are the right ones. Then there was the bad news. While eLearn clearly says to turn the pistons anti-clockwise to wind them in, “1. Use the tool to turn the brake calliper piston anticlockwise to move it back in its housing.” the piston only turned about 1/8th of a turn with the application of a fair bit of force before stopping. Measurement with a digital calliper over the ¼ turn it would move easily clearly showed the piston moved out when turned anti-clockwise. It took a lot of force to turn it clockwise and I was disturbed to see a small amount of fluid seep from under the boot. Nothing else to do but carry on, but sure enough after assembly I had a soft pedal and leaking calliper. I don’t know if I damaged the seal by turning it anti-clockwise, there was corrosion deeper in the cylinder or the hydraulic circuit was closed and I blew the seal. Maybe the ABS or hill-holder had closed the circuit, but eLearn gives nor info on that. As a precaution next time I’ll crack the bleed nipple before winding the piston in. So I’m now waiting for a recon calliper from Eurocarparts at £142 (less £35 deposit for the old calliper). Fortunately it was the right hand side that leaked as the left hand callipers don’t seem to be available. You can get a new piston and seal kit for under £20 but I don’t have proper facilities to clean the calliper and work on it. I’ve also never done one of the modern rear units with internal threaded adjuster and don’t have time to mess about with it.
Calliper arrives in two days so I’ll do the left side tomorrow.
Nearly forgot, the lining had separated due to rust.

Robert G8RPI

 

[varesecrazy]

So I got a set of pads and disks on clearance from an ebay seller for £47 and the good news is they are the right ones. Then there was the bad news. While eLearn clearly says to turn the pistons anti-clockwise to wind them in, “1. Use the tool to turn the brake calliper piston anticlockwise to move it back in its housing.” the piston only turned about 1/8th of a turn with the application of a fair bit of force before stopping. Measurement with a digital calliper over the ¼ turn it would move easily clearly showed the piston moved out when turned anti-clockwise. It took a lot of force to turn it clockwise and I was disturbed to see a small amount of fluid seep from under the boot. Nothing else to do but carry on, but sure enough after assembly I had a soft pedal and leaking calliper. I don’t know if I damaged the seal by turning it anti-clockwise, there was corrosion deeper in the cylinder or the hydraulic circuit was closed and I blew the seal. Maybe the ABS or hill-holder had closed the circuit, but eLearn gives nor info on that. As a precaution next time I’ll crack the bleed nipple before winding the piston in. So I’m now waiting for a recon calliper from Eurocarparts at £142 (less £35 deposit for the old calliper). Fortunately it was the right hand side that leaked as the left hand callipers don’t seem to be available. You can get a new piston and seal kit for under £20 but I don’t have proper facilities to clean the calliper and work on it. I’ve also never done one of the modern rear units with internal threaded adjuster and don’t have time to mess about with it.
Calliper arrives in two days so I’ll do the left side tomorrow.
Nearly forgot, the lining had separated due to rust.

Robert G8RPI

Shame about the growing bill.. but could easily have been far worse

 

[g8rpi]

So while waiting for the new RH caliper I tackled the LH rear pads and disks this evenng. It went a lot better. I can confirm that on the 1.9l 16V both rear calliper pistons must be turned clockwise to retract the pistons. This is the opposite of what eLearn says. I understand the 2.2 petrol and 2.4 diesel use the same callipers.
I'm pretty certain that I blew the seal on the other side by winding in the piston without opening the bleed nipple. I opened the nipple on the RH side and piton turned without excessive force but if I closed the nipple it locked up. It seems the ABS unit does not let the flui return to the tank. Seems obvous in hindsight, but it's surprising eLearn does not say anything about it. They give detailed instructions for other things that are obvious.
New calliper tomorrow.

Robert G8RPI.

 

[g8rpi]

ARRGH,
Picked up new calliper from ECP, took old one off completely, offered up the new one and it's the wrong size

I should have known when I noticed at the counter that the box had been opened previously. Looks like its the one for the 8V, slightly smaller piston.
So I took the piston out of the old one and it looks OK so I've ordered a seal kit (41mm) biggred4u on ebay and will give rebuilding a go. It will have to wait a few days as I have to go overseas for work.

Robert G8RPI.

 

[g8rpi]

So the seal kit arrived today and as SWMBO was out gettting her hair done I used the kitchen to do the rebuild. I didn't touch the seals on the handbrake / auto adjuster so job was easy. Just the main piston seal and dust cover.
Not put it back o the car yet though.


Robert G8RPI.

 

[g8rpi]

Back from a work trip (I've no time for people complaining about the heat were I was the car said 50deg C when I went for lunch and I was out in the heat part of the time) and fitte the re-built caliper today. All went well. I primed the cyliner with fluid using a syringe and with a full tank on the master cylinder gravity did most of the bleeding.
All working fine now.

Robert.

 

[s130]

All working fine now.
Robert.

A result then. Just what we all like.

 

[g8rpi]

So there has been one odd, but good side effect of re-building the rear caliper is that it's cured the long running intermitent dragging brake on the opposite front wheel. I'd spent a lot of time on the front wheel problem but never fixed it. If you did any work on the front brake it went away for a bit but came back. This made it very difficult to fault find. I thought it had gone away after working on the rear and was keeping an eye on the instant fuel consumption an brakke temperature. I changed the front pads at the weekend (pre MOT) as the faulty side was well worn down. New pads were fine, no temperature increase compared to the other side. The MOT garage conformmed toady theat there is no drag on that side.

The only thing I can think of that caused it was that heating from the slight drag on the rear was increasing the pressure in the cross-connected brake circuit and the bigger piston area in the front brake caused it to come on more. However I would not have thought that the ABS unit would have trapped the pressure. Maybe there was something stuck or blocked in the ABS unit and winding back the rear piston cleared it.

Robert G8RPI.

 

[s130]

The only thing I can think of that caused it was that heating from the slight drag on the rear was increasing the pressure in the cross-connected brake circuit and the bigger piston area in the front brake caused it to come on more. However I would not have thought that the ABS unit would have trapped the pressure. Maybe there was something stuck or blocked in the ABS unit and winding back the rear piston cleared it.

Robert G8RPI.

ABS units are quite complex little beasts