Rear Callipers

In the words of a noted presenter... "How hard can it be?"

So I thought I would at least attempt the clean up and servicing of the rear XJ6 callipers. All they are made up of is two chambers bolted together with a piston in each, linked by a pipe to transfer fluid between the two sides plus bleed screws.

So here is what they looked like in their unwashed state before removing the (overly complex - that's a separate post coming up) handbrake callipers. The handbrake parts are removed leaving just the single pot disk brake parts.

I have already split these apart - unlike the front callipers there isn't a seal between the halves so just a case of undoing the 4 bolts - torqued to a value known as FT.

Once undone the fairly rotten rubber boots peel off leaving the inside of the piston exposed.

Looking at the muck you'd think these things have been totally compromised but you can't really tell until you get the piston out.

Which I confess I foolishly thought would be dead easy. A bit of prying with a screwdriver and they'd pop out I thought. Wrong!

After prying, head scratching and self beratingly telling myself off for believing I was able to do this I resorted to the internet. After reading tales of people firing calliper pistons with compressed air and them then embedding in brick walls my fears grew (not least because of not having a compressor).

And then eureka. The grease gun method. Brilliant. One order to Machine Mart, one order to the Nipple Shop - yes it does exist and it's valid - for grease nipples to fit where the hydraulic lines connectors (3/8 UNF incase you need the info) and then pump.

 The pressure that the grease gun delivered is in the region of 10,000 psi and unlike air it does not compress. A rather immoveable force against which the piston is powerless.

Simply keep pumping until the piston is free. Clean out the new grease and clean out / check the bore and remove old seal ring.

Cleaned up and then painted with VHT Calliper paint they look as good as new. Now just need to source seals and new pistons. Whilst the old ones look in reasonable shape if I'm putting new seals in it makes sense to put in perfect new pistons to ensure full integrity and no opportunity for pressure / fluid loss.