This is the second in a series of articles over the course of several months that are focussing upon the repair, maintenance and troubleshooting of the braking system of Series I, II and III Land Rovers. Last month the focus was upon squealing brakes and binding brakes. We look at two further possible topics of concern with the braking system this month.
Brake pedal travel is excessive
This the situation when the brake pedal travels a significant distance towards the floor before you feel hard and firm resistance; it can have several possible causes and it is best to tackle the problem as soon as it is noticed. If the probl
em is allowed to develop, and you have to press the brake pedal almost to the floor before braking commences, then you have no margin for error should a little air enter the fluid system via a damaged seal, or a brake shoe loses its set adjustment. This scenario is of particular concern to drivers of Series I, II, IIA or early III Land Rovers as these models have only a single circuit braking system.
The first place to check for a problem is at the business end of the system - where the brake linings contact the brake drum. All brake shoes are adjustable as to the distance they remain from the drum lining when they are not in use. This distance is the main reason why the brake pedal descends a little before any pedal pressure is felt and actual braking action is observed. In the case of Series I and II LWB models, the brake shoes have a single adjuster between the brake shoes which operates on a plunger system, whereas all other models have one cam adjuster for each individual brake shoe. Over time, these snail-shaped cam adjusters have their serrated edges worn down and they tend to slip over the steady post they rest against. Parts catalogues list these cam adjusters as an integral part of the brake back plate but a brake adjuster repair kit is available (part No. RTC3176); the kit supplies adjusters for one complete axle. Each individual replacement adjuster bolts together, and over time, if the two components become loosened, then it becomes possible to rotate the cam adjuster around completely without actually moving the location of the brake shoe. This is easily resolved by just gaining access to the adjuster and tightening it up. There is usually no need to remove the brake shoe to achieve this adjustment.
When setting the brake shoe adjustment, it can be done by jacking up the vehicle and leaving the wheels on, but it is more accurately done, and more likely to gain you better mileage economy, if each wheel is removed in turn; supporting the vehicle supported on axle stands. The brake drum can then be more sensitively adjusted for free movement. You can also whilst gain access to the shoe adjusters without having to get underneath the Land Rover. When adjustment has been made, it is important to depress the brake pedal a few times to centralise the brake shoes and ensure that clearance has been maintained before re-fitting the wheel and lowering it to the ground.
Brake pedal feels 'spongy'
This is the situation when there is no hard and firm resistance felt at the pedal as the brakes are applied. It can be confirmed by rapidly 'pumping' the brake pedal up and down - the 'sponginess will disappear and firm resistance will be felt. But the next time you depress the brake pedal, the 'sponginess' will reappear.
This problem is most commonly caused by a small amount of air (a bubble)
somewhere in the brake fluid. The strategy is to find out roughly where this air bubble is, and then flush it out of the system - a technique widely known as bleeding the brakes (earlier homepage).
To help locate where the air is, it is useful to be able to clamp the flexible rubber brake pipes to prevent the flow of brake fluid through them when the brake pedal is depressed. This reduces the volume of brake fluid under investigation by eliminating the brake fuid beyond the clamp(s).
If there is a flexible rubber brake pipe leading to the back axle, then this should be clamped first, as it will indicate immediately if the problem is located on the rear axle or elsewhere. If it is on the rear axle then bleeding the brakes should start with the rear wheel furthest from the brake fluid reservoir and then proceeding the other rear wheel. There will probably be no need to bleed the front wheel system if the pedal was firm when the rear pipe was clamped.
If the problem is not on the rear axle then the individual problem wheel can be identified by clamping the flexible brake pipe on each front wheel in turn. If the brake pedal becomes firm, then the clamped wheel is where the problem is. You may be able to solve the problem by simply bleeding the fluid from the offending wheel cylinder. But if this fails, then it could be that there is air in more than one place and then you need to start with the rear wheel furthest from the brake fluid reservoir and then bleed all the wheels individually.
Another possible cause of loss of brake pedal pressure is leakage past one of the rubber seals in the system. Rubber tends to perish and harden with age and so then provides a less secure seal under pressure. Rubber seals are located in each of the wheel brake cylinders and also in the brake master cylinder. A damaged wheel cylinder seal can usually be spotted by a slight leak of brake fluid from the cylinder itself, but you need to remove the associated brake drum to inspect for this. Wheel cylinder repair kits are available, but if there is any corrosion on the cylinder wall then a new brake cylinder is required.
The only real way to confirm a brake master cylinder
seal failure is to completely bleed the brake system then clamp all the flexible brake hoses simultaneously and check the brake pedal for sponginess. If it is not firm then probably the seals in the master cylinder are the cause. Repair kits are available with new seals. New brake cylinders are available froma numbe of sources but avoid some cheap ones. Don't risk your life for a few extra pounds.
Finally, there is also the possibility that a flexible rubber brake hose has become weakened somehow, and is ballooning out slightly under pressure. This is unlikely to be visibl,e
unless the hose is clearly damaged. You will need to apply clamps diagnostically to locate the problem.
Photo showing improvised brake bleeding kit, using a transparent tube and an empty washing-up liquid bottle.
You can block the end of the tube and slit it above the blockage to facilitate 'blow ... but no suck'.
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