Rear Callipers part 2

Right, back from many trips to Ireland visiting a customer plus a holiday in Devon I'm ready to finish off the rear callipers (thanks to Ed Ward of Wards for supplying the parts at a reasonable cost) by a final clean out and rebuild.

Not going into masses of detail here, summary is that the halves need a very good clean and de-dust. Using red rubber grease on the seal insertion and pistion insertion. Pop the dust boot and ring on and then put the halves back together and then assemble the hand brake callipers onto the completed brake assembly. All pretty straightforward.

Rear hubs, front callipers

I have been undecided about whether to send rear hubs off for refurb or do myself. There are some relative complexities when putting bearings in to ensure the correct amount of float - i.e. play in the bearings to ensure they are running at optimal pressure, not too tight or loose.
There's videos on youtube showing how and plenty documented too.

I looked at costing up all the parts for the bearings etc to do the refurb and realised it was going to be cheaper to send to Wards to get a better result! The final thing that did it was whilst it took alot of thumping just to free one hub from it's bearings I then I discovered that someone in the past had clearly mashed one of the wheel studs and instead of replacing with another stud, had welded a bold through from the other side of the hub!

I can't imagine what this did to the balance of the rotating assembly but in the end speaking to Ward's they could resolve relatively easily...

Given that I would be sending off to Wards I sent the front callipers too.

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.

Two posts in the same day... well, trying to get the hang of this blogging site and catching up on bits hit - and it does seem to mainly be hitting things that gets them apart - I got behind with the narrative.

One lone front caliper - not much for several hours work.

Front hub carrier - amazing how much stuff gets picked up and stuck to these things but I guess not surprising for a 17 year old car. I gave the end closest to bottom with photo with a couple of taps of the rubber mallet to get the stub axle out for it to shoot 6ft across the garage in a beautiful ballistic arc and dent the garage door.

Still thinking about how I'm going to clean all the grease and crud off. The Sand / grit blasters I've spoken to don't like grease as it plays havoc with their machines. Researching online there are a number of products that claim superior degreasing capabilities - I have a feeling this will be a trial and error process.