STRIPPING THE FRONT BRAKES
ON THE earlier Tdi Discovery, Range Rover and Defender models, changing brake discs could be a tricky job. On those models not only did the brake pads and caliper need to be removed, but the hub had to be taken off the axle in order to remove the old disc. This invariably extended to re-packing bearings with grease, replacing the oil seals and fitting new hub gaskets.
It’s easier with the P38 Range Rover and Discovery 2 models. Each disc is held on the hub by a single grub screw. When that is removed, the brake disc slips straight off over the studs.
THE DESIGN of the rear braking system on Discovery 2 and P38 Range Rover is very similar to the set-up on the front. However, unlike the front discs which are of the vented type to assist cooling, the rear discs are solid metal and the calipers are much smaller (front brakes do most of the work because, under braking, the weight of the vehicle tends to load onto the front wheels). But everything is dismantled in a very similar fashion. Again, there is no need to remove the hubs, thus making the job faster and easier than on earlier models.
REBUILDING THE front and rear brakes on the Discovery 2 and P38 Range Rover is as easy as taking them apart in the first place – or arguably easier, without rusty or seized parts to deal with. However, the braking set-up is the most vital of systems and must be built up in an organised and methodical manner to ensure that there are no errors. The old adage of check and double-check again is very important with brakes. With that said, there is little that can go wrong, particularly as the stripdown has just taken place and is fresh in your mind and all is correctly bolted up.
The front brake caliper is held to the carrier by two flange head bolts. These bolts are removed with a 12 mm hexagonal socket wrench. With the two bolts removed, the brake caliper can be eased off the carrier and pads, using a suitable pry bar or large screw driver. As the brake caliper is lifted clear, the brake pads are revealed. They are held in place by slots in the carrier and appear to be quite worn.
The old brake pads are eased out of the carrier and are discarded into the metal recycling bin. Brand-new brake pads will be fitted all round. The brake carrier is fixed to the hub by two special bolts, with a 12-sided head. They are removed with a 14 mm bi-hex socket wrench. It is good practise to replace these bolts as a matter of course. With the rusty head, they will probably round at any future attempt at removal.
After successful removal of the bolts, the carrier is withdrawn and inspected. They are generally reusable unless the upper springs have seized. The brake disc is held to the hub by one screw. Correct Pozidrive #4 screwdriver prevents head damage. If tight, try tapping the disc’s centre hub. A gentle tap with a soft hammer will probably be enough to ease the old disc off the hub, and over the wheel nut studs.
All four of the brake discs on the Discovery are well worn and near to the end of their life, so new discs and brake pads are the minimum requirement. The brake calipers will be replaced too, so flexi hose is disconnected. Otherwise the caliper could be safely tied up, with the hose still attached.
As the single-pot rear brake caliper is removed, it can be seen that the cylinder itself is rusty. This will stick if pressed in to fit new brake pads. The rear brake pads are well worn and look somewhat glazed, so their braking performance will be well down on what it should be. The rear brake carrier is removed in much the same way as the front one, using a 14 mm bi-hexagonal on the 12-sided bolt head.
The carrier is now withdrawn after the bolts have been removed. The spring action will be tested, checked and lubricated ready for subsequent refitting. The screw securing the brake disc to the hub is removed and the disc tapped off over the wheel studs as before, using a rubber-faced mallet. The rear discs are not showing as much wear as the front brakes, but will be replaced with fresh new ones, due to some grooving in the surface.
The rear brake calipers are in poor condition, and externally pitted (though this will not impair performance) and they’re ready for replacement. Following removal of the flange bolts, the caliper is levered off the carrier in a very similar way as the front calipers were removed.
The new bolts have clean, sound 12-sided heads, which will be removable at the next brake service. Old rounded heads are difficult to remove. The caliper carrier bolts are initially tightened using a 14 mm socket wrench. They should then be tightened with a torque wrench to 129 lb ft. The new front brake calipers are OEM quality parts from the Britpart range and come complete with new bleed screws and bleed screw covers.
The shiny new vented brake disc is fitted over the studs and onto the front hub, ensuring that the screw hole is in line with the threaded hole in the hub. Copper grease has been applied sparingly to the disc securing screw thread, before it is tightened in position using the Pozidrive #4 screwdriver. New OEM quality bolts are used to fit each of the four brake caliper carriers – front and rear – with thread lock adhesive applied to all of the threads.
Before each of the brake calipers are fitted, new brake pads need to be put in place. These brake pad kits are supplied with new guide pin bolts. The new brake pads slot into the carrier in such a way, that they are conveniently held there, ready for the caliper to fit over them. The pistons in the new calipers are fully retracted, so fitting the caliper in place is very easy, with lots of clearance over the brake pads.
The front brake discs on Discovery 2 are of the vented type – the two friction surfaces are separated by an air cooling gap to improve efficiency. All of the new brake discs are cleaned using a brake cleaner solvent solution to remove the protective greasy coating applied at the factory.
The old and tired original rubber brake flexi hoses are being replaced – and upgraded – with this set of braided performance hoses. The brake flexi hose is fitted to the caliper with a banjo bolt. New copper washers are supplied with the hose kit. The front hoses will be attached to the brake pipe ends, still plugged with blank connectors (arrow) to keep fluid in and the ABS pump primed.
At the rear, a new copper brake pipe has been made and connected to the braided flexi hose – and fixed to the mounting bracket. The four brakes are now ready for the braking system to be bled via a vacuum bleeder, pulling new fluid through each circuit and expelling air.