Rear pads binding, 306 HDi

[moodle]

I posted this across on the Citroen forum, no answer or clues so far, have done an extensive search but nothing simialr as yet:

Hi,

I have a really annoying problem which I havent been able to solve.

A while back I changed the rear pads on a 2001 HDi 306 Pug, no problems there wound back the piston and wedged in the new pads. Ok, it was a bit stiff to turn but I thought after a couple of miles they would bed in, but they never did.

Instead it seems as though the pads were permantly binding with the disc which I put up with until the current change of pads. When I took the old one out one was at an angle and certainly looked like it had been rubbing over a long period of time.

I replaced the pads again checking everything meticuously and winding back the pistions the their full extent, sloted the small pin into the grove of the disc on both pads - started the engine and pressed the brakes, took up the slack and all was fine, but no ! guess what these bind exactly the same as well.

The only thing I havent checked is the hand brake but pulling it up it travelas a long way before it engages - anyone any ideas


Thanks,

David

[AndersDK]

Hi David -

As mentioned in a Citroen thread, there is a common problem on PSA rear radius arm fitted brake calipers.

The problem is that the caliper alloy body tends to build up corrosion in the joint seat arm to caliper body. This corrosion will over time press the caliper body to sit in an angle relative to the disc, such the pads wear un-evenly.
This in turn causes binding pads, as there is a consequent sidewards force on the caliper pistons, making them stick.

The remedy is to remove the caliper complete and then clean the mating faces on radius arm and caliper body - using a file to re-generate a clean & level surface.
On reassembly the joint is treated with a smear of antirust mass, to seal off against penetrating salty water.

The same is true if the caliper is not directly fitted to the arm - but slides on bushings. Here the joint bushings to radius arms may show exactly the same problem, again making the caliper sit in an angle.
Remedy is the same as above, yet you will need new bushings as you can not hit the correct level end surface on the bushings if they are severely corroded.

[moodle]

Hi David -

As mentioned in a Citroen thread, there is a common problem on PSA rear radius arm fitted brake calipers.

The problem is that the caliper alloy body tends to build up corrosion in the joint seat arm to caliper body. This corrosion will over time press the caliper body to sit in an angle relative to the disc, such the pads wear un-evenly.
This in turn causes binding pads, as there is a consequent sidewards force on the caliper pistons, making them stick.

The remedy is to remove the caliper complete and then clean the mating faces on radius arm and caliper body - using a file to re-generate a clean & level surface.
On reassembly the joint is treated with a smear of antirust mass, to seal off against penetrating salty water.

The same is true if the caliper is not directly fitted to the arm - but slides on bushings. Here the joint bushings to radius arms may show exactly the same problem, again making the caliper sit in an angle.
Remedy is the same as above, yet you will need new bushings as you can not hit the correct level end surface on the bushings if they are severely corroded.

Thanks Anders for such a detailed reply,

I really couldnt understand what the problem was but this makes a lot of sense.

I must have freed off the calipers somewhat when I removed them this time as the binding quickley stops when you pull away. Now I know what it is I can do something about it, if its helpful to other folk I will take a few pics along the way and post them back here.

Best,

David

[moodle]

Havent forgot this but busy with Merc project at the moment - as mentioned will post back a few pics as there seem to be quiet a few threads on brake related issues

[moodle]

Ok, going to tackle the pads this weekend - Pug has been off the road while doing the Merc project.

Can anyone recomend a good grease to apply after the cleaning (as above), had a quick look in Halfrauds and there is a who line of copper, moly and such.

TIA

[CitroJim]

Personally, I use copper grease but the better one is the stuff that is just like copper grease but is aluminium if you get my meaning. Trouble is, it is not easy to get hold of.

I saw in another thread somewhere about using a sheet of polythene between the caliper and trailing arm. That seems like a cracker of an idea as that'll stop the electrolytic corrosion dead in its tracks. Just make sure the through bolts are a very tight fit in the polythene and coated with copper grease.

[moodle]

Personally, I use copper grease but the better one is the stuff that is just like copper grease but is aluminium if you get my meaning. Trouble is, it is not easy to get hold of.

I saw in another thread somewhere about using a sheet of polythene between the caliper and trailing arm. That seems like a cracker of an idea as that'll stop the electrolytic corrosion dead in its tracks. Just make sure the through bolts are a very tight fit in the polythene and coated with copper grease.

Thanks Jim,

Once i have got the wheels off in the dry I can have a look at the best approach - did I see you having the same problem on another thread? something about piping and 12mm tube to improve them?

Cheers,

David