The Range Rover’s brakes were becoming less effective and I was getting frequent ABS and ETC warning lights, so I had to make time to fit the Zeus stainless steel calliper pistons I bought a while back (identical to those I fitted to the callipers on the brakes of the new axles for the 109).
The callipers were tackled one at a time, removing the pads first, pumping the pedal hard to extend the pistons from their cylinders, clamping the hoses and then removal of the calliper. Once removed to the workbench, they were split into their halves and the vice was used to pull each piston from its bore. This results in a lot of spillage, so make sure you have plenty of rags and make sure you do this well away from any flame or strong heat source – hydraulic fluid is inflammable.
With the pistons removed, the seals were hooked out of their grooves. In most cases, the outer “sweeper” seals and their retaining rings came off with the pistons. They’re not meant too – the pistons were just that rusty. The bleed nipples were removed (as were the blanking bolts on the rear callipers) so that all of the internal passageways could be cleaned out with a small steel rod. The pistons’ bores contained a large amount of grey “jelly”, some sort fungus that grows in the brake fluid, presumably once the fluid has ages and absorbed water. It is quite shocking how much filth accumulates inside the calliper cavities.
After a thorough clean out, including brushing and chipping away the external rust, soaking and flushing in petrol, the new seals were fitted. Make sure the seal grooves are scrupulously clean to prevent leaks, and ensure the outer seal grooves are free of all rust and are cleaned back to smooth metal, not rusty, in order to allow the retaining rings to fit without catching and distorting. Those can be tricky to fit, so it’s worth having several spares.
With the seals fitted, the bores were doused in fresh brake fluid and the pistons smeared with more before being inserted into the bores. Make sure that you fit them the right way – the hollow sides face the pads, and front calliper pistons are mush deeper than rears, though both have similar diameters. If the piston’s rim sits proud or recessed below the calliper’s surface once pushed all the way in, you have the wrong sort of piston fitted – the piston length matches the depth of its bore.  The calliper halves were then rejoined (vented disc callipers have an insert between the two halves), the bolts given an application of red (permanent) thread lock. The bleed nipples and blanking bolts/plugs were refitted and the completed calliper then cleaned and painted (black Hammerite).
The callipers were refitted, followed by the pads (make sure you refit them in their original locations if re-using the same ones) with a smear of copper grease on their backs. Bleeding the brakes on power assisted, ABS equipped systems is not like on simpler systems. There is a very specific sequence and technique to bleeding the more advanced systems, so make sure you have the appropriate manuals or have the vehicle delivered to a suitable garage for this part of the job – it’s quick compared to the calliper work, so won’t cost much but could save your life. You may also notice another new addition – heavy duty drive flanges on the front hubs to try to hold the stub axle and CV more securely, preventing the CV drifting out of range or contacting the ABS sensors in the top swivel pins, hopefully ridding me of the warning lights.
So far, so good. The brakes are really sharp and no longer drag, and I have had a clear dash once the warning systems self-test is completed on start up.
nice report! do you know if earlier type AP brakes on RRC has different calipers from Girling braking system or both use the same calipers? or should I first split the calipers prior to ordering pistons (it takes a month to get it delivered)
BTW, reportedly, landrover handbook prescribes to avoid splitting into halve – nobody knows why. You have any guess?
I know the callipers vary with age in several ways, with front callipers having one or two hose connections depending on model and year, and different models having different size callipers and pads. The calliper sizes vary not only to suit bigger pads, but also to accommodate wider or larger diameter discs, so compatibility needs to be checked carefully. While the combination of discs, callipers and brackets used on my Salisbury modification doesn’t match on paper and the clearance between the disc and the groove in the calliper is smaller than normal, they do work together. That isn’t the case for some combinations.
My RRC is one of the last built and has bigger callipers than the Discovery units used for the 109. The pads also fit with a different retaining pin and spring system. The RRC front brake discs are also vented, so the callipers have a spacer block between the halves.
I’d be guessing at why LR advise against splitting callipers, but I suspect it’s because the O-rings that seal each half’s fluid passages to each other aren’t easily available and because any dirt, damage or corrosion on the mating faces on reassembly would render the calliper unserviceable. However, if care is taken when working on the callipers and the bolts are correctly torqued, I see no reason that clean, undamaged callipers can’t be returned to service. Splitting them is the only way to replace the pistons and seals and is the only way to remove the dirt and biological growth from the fluid filled areas.