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[PtP]

I know some of you will have seen this before, but I thought I’d post it here before it gets lost when I pull the JA site.


Well, I thought I would tackle the job and I’m glad I did so far as the job has been very easy.

I thought I would get away with just stripping the calliper, cleaning the rust and crud and rebuilding it!

Not quite as straight forward as I first thought.

I stripped the piston out and discovered there was a ridge of rust deposited around the edge and I also discovered that the piston is not made from steel, but some sort of resin material / Bakelite. Anyway, a very light rub on some 600 grit wet and dry and the rust deposit was removed.

This photo shows the piston after I removed the rust.



Next I realised the rust had come from the ring of metal by the seal in the casting.



So a gentle rub with the 600 paper and all the rust was removed.



In the process of rubbing this area of the cylinder, I realised that there must be a split in the outer seal to have let all the water in which had caused this to rust up. Sure enough, here is the split.



A quick call to Lighthouse who have the service kits in stock and I’m now waiting for the post in the morning.

Knowing that there is a new piston on its way I removed the internal seal from the cylinder and inserted the piston and to my surprise it got stuck despite having removed all the crud and rust! In some positions it was working, but if I rotated it a few degrees one way or another it became stuck again. I very gently rubbed the piston again on the 600 paper and now it’s a perfect fit! I will use the new piston though. But it just goes to show, what you thing is clean and back to size is not! I also rotated the piston in the cylinder after this second sanding and there was no sign of any interference, just a good close and snug fit.

The service kits include the piston, inner seal and outer seal are only £13.90 plus VAT and p&p. I’ve ordered 2 sets!

[PtP]

Just a follow up to this thread, since I’ve done this original service.

I’ve had to rebuild the callipers twice (once every couple of years) using the existing parts, as rust had built up in the same area again on both occasions restricting the piston movement. The last time I rebuilt them, I put a very light smear of Locktite silicone sealer around the edge of the outer seal where it sits in the casting to help prevent water ingress.
 
With hindsight I suspect I’d blasted the callipers too much with my pressure washer whilst cleaning it off and the water has got in past the seal either around the Bakelite or the casting. I think from now on I’ll keep the pressure washer away from the callipers.

[Dave69]

The same process can be used for the xj, complete kits like Pete has mention are available from lighthouse or he sells the seals seperate, For what it costs it's worth spending that little more for the complete set. Fit the rubber seal to the piston first then push the seal to the inner most part of the piston so that the seal looks like a skirt, then fit this "skirt" into the caliper as there is too much movement in the seal to fit the piston after the seal is fitted to the caliper