Brakes

[KemppiFrog]

Mate has a Citrôen C15d van that he mostly uses around the estate of the Château that he looks after.
Nasty noise from the brakes, so he buys pads and a Haines book. Takes one side to bits cursing Haines...as they are different to the book. Pads are only slightly worn, so he moves to the other side, where they are metal to disc. He can't get the piston in the caliper to retract, so asked if I could help.
No way would the piston go back, so I removed the caliper and disconnected the hydraulic hose. The piston went back with finger pressure?? I thought it was seized. Then a little bell rang, years ago, I had a similar prob on an R4; The brake hose had degraded inside and acted as non return valve, so the piston was always under pressure, therefore chewed up the pads.

Anybody else had this one?

 

[Woody.v8]

Mate has a Citrôen C15d van that he mostly uses around the estate of the Château that he looks after.
Nasty noise from the brakes, so he buys pads and a Haines book. Takes one side to bits cursing Haines...as they are different to the book. Pads are only slightly worn, so he moves to the other side, where they are metal to disc. He can't get the piston in the calipher to retract, so asked if I could help.
No way would the piston go back, so I removed the calipher and disconnected the hydraulic hose. The piston went back with finger pressure?? I thought it was seized. Then a little bell rang, years ago, I had a similar prob on an R4; The brake hose had degraded inside and acted as non return valve, so the piston was always under pressure, therefore chewed up the pads.

Anybody else had this one?

Yep, about 3 times now, it's one of those things you struggle to get your head around ,so go in search of something more complex.

 

[p0689109]

On this subject, my LDV Convoy 400 has a brake problem that is causing me no end of pain and anguish. Not long after emptying it off my mobile workshop/ DIY mobile gear (so that I could help my lad move house) I have had a brake problem Now the van had been loaded with the gear. and more sometimes, and so the load leveller for the rear brake had not been exercised through its range a lot. The defect is that if the vehicle is left standing a long time, which it is as it only gets used if there's something for it to do as its not a working van, the first press of the pedal and I found the back brakes lock. Luckily I was only going about 5mph when it happened and all that happened was for me to remember to change kecks on getting home. I then found that to get the brakes to unlock required the van put in reverse and hey presto all is good. The rest of the journey was good and so it was for the next few journeys. But over time this happened again and so I bit the bullet and decided to buy a new load sensing valve. Fitted it and set it up as per the manuals and graph for the vehicle. Again all seemed well until it came back. The occurrences were increasing as, instead of just the first brake operation, it was extending to two and three before it stopped happening and all would be well. Of course during the first few try's I did not go very fast as you only had to touch the pedal for it to happen. Now I had put new shoes on at the back and all was well as regards the brakes mechanisms, pistons nice and free movement, handbrake mechs good etc and this was done before the Mot through which it passed clean. But just to be doubly sure I got a new shoe retaining kit of pins and springs etc and replaced them and adjusting the brakes as per manual. Again the beast came back and so I decided to replace the one flexi hose that joined the feed from the master cylinder to the back system thinking exactly what you found on the Citroen. But no, no fix. Now the only thing I can see is the master cylinder being the cause. What do you boys think. But now here is the killer blow. You cannot get this particular cylinder anywhere in the world as the machine that makes them is broke and they have not been able to fix it! I have managed to get a seal kit from a firm that does overhauls on them but even they cannot supply all the bits. I am loathe to start the swap but do you think like I that a seal in the cylinder could be lipping and acting like a NRV? Now normally how many master cylinders are changed on cars as a regular occurrence? In the grand scheme not many I would think. But for the suppliers to run out of this particular model sounds suspicious to me!

 

[KemppiFrog]

I had another one on an R4. I had a mild rear-ender in slow traffic on a wet road. No grief for the guy i hit, but I was puzzled because I didn't seem to brake properly and heard the rears lock. Short story: If I braked normally, the system worked fine, but if I tapped the pedal quickly, only the back ones came on. Changed the master cylinder and all was well.

 

[Turbo]

Anybody else had this one?

Had this on my 406.

 

[Touchdown]

Little trick i was taught is to crack the bleed nipple when putting pressure on the piston. Fronts usually retract with little pressure and rears need a little more thinking about with the left or right hand thread twist motion.
I also bleed brakes every year, put silicone grease on visible bit of piston and red rubber grease in grouve where gaiter fits on piston...prevention better than cure.

 

[slim_boy_fat]

Don't some pistons nowadays need to be wound back?

 

[Wallace]

Don't some pistons nowadays need to be wound back?

Usually calipers with the handbrake.

 

[KemppiFrog]

Little trick i was taught is to crack the bleed nipple when putting pressure on the piston. Fronts usually retract with little pressure and rears need a little more thinking about with the left or right hand thread twist motion.
I also bleed brakes every year, put silicone grease on visible bit of piston and red rubber grease in grouve where gaiter fits on piston...prevention better than cure.

The only problem with easing the bleed nipple, is that it would have masked the problem with the hose. So we would have reassembled the brake and had the same wear on the pads.

 

[p0689109]

Mr Fuzzy As mentioned I checked the pistons for freedom during the rear brake shoe replacement and they were good. having said that I have bought 2 new ones in case the master cylinder is not the problem. But it was/is strange that when they locked on they released when reversed a touch immediately.

 

[CompoSimmonite]

Our Chrysler Neon was diagnosed with ABS module fault by main agent who wanted £1500 + labour + vat to sort out. I did the repair myself and cost £26 as all that was wrong was front flexible hoses that were also acting as one way valves !
BTW main agent, Cumbo's, went bust !

 

[123hotchef]

Don't some pistons nowadays need to be wound back?

some yes some even need a computer to tell them to retract

 

[garethp]

some yes some even need a computer to tell them to retract

My dads mate owns a garage and whilst talking to my dad about brakes he mentioned that some (I think) mercs have plastic gears in the mechanism in the rear calipers, if the caliper isn't spotlessly clean when you use the computer to rewind the piston it strips one of the gears and of course the gears aren't available as spares so a caliper is needed.

 

[Turbo]

Some abs systems don't like you forcing the pistons back & pushing the fluid backwards through the system. On most modern cars it's recommended to release the bleed nipple before pushing in the piston, just to be on the safe side.