Xantia rear brake pads - looking bad

addo · Post by **addo** » 07 Sep 2010, 10:21

Mike T wrote:I also want to question the wisdom of using copperslip where corrosion occurs between two dissimilar metals? Would a tri-metal meet be even worse?

Hi Mike,

There are indeed shims and an anti-rattle clip in the X2 rears.

As to copper grease - there seems to be a great deal of difference between brands. The standard issue CU grease is maybe not a good idea, but the Wurth CU-800 is quite a different animal - the grease base being very waterproof. As it's water ingress that's crucial to "driving" the dissimilar metals reaction, you are starting well ahead.

However! It's the water repellent aspect that's needed; the "wire rope grease" cited recently sounds excellent. It's just that copper grease is really handy for other car jobs...

Cheers, Adam.

Post by **myglaren** » 07 Sep 2010, 10:23

MikeT wrote: I also want to question the wisdom of using copperslip where corrosion occurs between two dissimilar metals? Would a tri-metal meet be even worse?

It does seem to be a fairly obvious flaw in the hypothesis but in practice it seems to work.

Someone (apologies, forgot who) advocates the use of rope grease, which seems a reasonable solution for anyone able to get some without jumping through hoops - it is quite expensive to buy 'over the counter'
I reckon a gasket made from polythene or even better Teflon of mica would do the trick.

Mine were just greased with LHM (I didn't do them) and appear to be ok, about time to do them again as a preventative measure though (2 years).

Xaccers · Post by **Xaccers** » 07 Sep 2010, 10:55

Careful no one uses a shopping bag as these are now biodegradeable making them useless to store things in too (unless you like filling your workshops with plastic bag dust!).

MikeT · Post by **MikeT** » 07 Sep 2010, 11:05

So much for the Gold Service (that shows the spark plugs were changed) in this car's history!

After I'd refitted the caliper with (Carlube) copperslip did I remember a little tube of PAGID CERA TEC anti-squeal lubricant I once bought just for this occasion. I was actually trying to hunt down aluminium grease at the time when a GSF assistant mentioned this non-metallic brake grease so I bought it. Best I make use of it and get the copperslip off.

Another worry surely must be the now pitted and contoured caliper face - surely such air gaps will allow it to corrode that much quicker? Has anyone had their caliper mating surface skimmed, can it be done or will it eventually lead to new calipers?

Post by **RichardW** » 07 Sep 2010, 11:14

Mike,

When I did the ones on my first Xantia which were heavily corroded (so much so I had to saw one the brake pads in half to get it out of the caliper!) I filed the surface flat before refitting - you will probably need to do this to get the caliper to sit centrally over the disc anyway. Of course you will notice that the calipers are only handed by the location of the feed pipe and bleed screw

So if you want a nice new flat face just swap them side to side, and swap the bleed screws to the other hole - you will need to have the bleed screws out anyhow to bleed to the brakes afterwards. Heat, Plus Gas, a 6 point 8mm ring spanner and patience are required to extract the bleed screws intact!

Old-Guy · Post by **Old-Guy** » 07 Sep 2010, 13:30

RichardW wrote: ...Of course you will notice that the calipers are only handed by the location of the feed pipe and bleed screw. So if you want a nice new flat face just swap them side to side, and swap the bleed screws to the other hole - you will need to have the bleed screws out anyhow to bleed to the brakes afterwards. Heat, Plus Gas, a 6 point 8mm ring spanner and patience are required to extract the bleed screws intact!

Like so many of the best ideas, so obvious and simple once some clever Richard has pointed it out.

I found that, after an overnight soak with PlusGas, a decent 'flat-driving' ¼" drive socket on a 'T'-bar (to avoid side-ways load) was deep enough to get my bleed screws undone without any trouble.

MikeT · Post by **MikeT** » 07 Sep 2010, 15:40

The surprises keep coming - the wheel bolts were no more than finger tight on the O/S rear! There's a head missing off one of the bolts holding the torsion bar to the chassis. Shims and springs also missing of this caliper as well as wrong pads fitted and worn at an angle.

Oops, I sheared the pad retaining pin on the O/S caliper - Toby to the rescue again by robbing his Activa's pin so I'll get him a new replacement this afternoon or tomorrow.

The caliper bolts came out easier this side but there was roughly the same amount of corrosion.

Great tip about them being ambidextrous! I would certainly think about painting/protecting the surface somehow, probably make a gasket from water-resistant material. Hopefully, this won't be a job that needs revisiting again in my ownership?

I'm happy to say Xantia bleed nipples have never given me trouble unlike just about every other vehicles I've worked on.

All back together - minus shims and springs and ready for a touch of Citrobics before I head off to the Stealers.

Thanks everyone for your advice, suggestions and input