I am running standard Cortina uprights with Girling callipers. I have had a piston or two sticking in the past and after freeing them up by winding them in and out it has cured the problem for a while. Just had my MOT and the tester says the braking efficiency is just the right side of failing so I have decided to rebuild them with new pistons and seals and a full repaint. I have read that you shouldnt split callipers but I see no reason why. I want to give them a full clean up and paint so as long as the mating surfaces are totally clean and the O ring seal is in perfect condition when reassembled why not? Any comments?

the O ring should be replaced as it swells with the brake fluid,the O ring is AFAIK not available hence the reason.

The rings are available. I bought a spacer kit for girling 16pb calipers, and it came with the rings.

Try big red?

From much earlier posts here, and from former colleagues at work (Girling) the bolts holding the 2 caliper housing together have to be replaced. And they are (or were) unobtainable.

I rebuilt my old M16 calipers without splitting them. Just replaced seals and pistons.

Have you seen the price of new ones compared to the price of the rebuild kit new bolts and paint etc? Unless you really want to do it just because you want to(nothing wrong with that) its better to buy new,

http://www.rallydesign.co.uk/product_info.php?cPath=562_1182_1189&products_id=10537

Then stick yours on ebay for some else to refurb.