What do I do if my brakes fail?

Why a hard pedal is not a failed pedal, the order of things to try, how to use the gearbox and the parking brake to slow a car, and what actually stops it.

Difficulty: intermediate
Time: 12 min
Read: 5 min
Safety: restricted

Short answer

Press the brake pedal hard and pump it — dual-circuit systems mean one half often still works and pumping can restore pressure. If the pedal is rock hard rather than soft, the servo has failed: the brakes still work but need far more force than you have ever used. Lift off, change down through the gears for engine braking, and apply the parking brake progressively rather than in one movement. Get off the carriageway; an uphill gradient or a rough verge scrubs speed.

Every car sold in the UK for decades has had a dual-circuit braking system, split so that a single hydraulic failure leaves you with braking on two wheels rather than none. That design is why genuine total brake failure is now extremely rare, and it is why the first thing to do is press harder rather than panic. The far more common experiences are brake fade, where the brakes have overheated on a long descent and have temporarily lost their bite, and servo failure, where the vacuum assistance has gone and the pedal feels like a brick — in which case the brakes are entirely functional and simply need several times the pedal force you are used to applying.

Safety

Complete brake failure on a modern dual-circuit car is very rare, and almost every case people describe as brake failure is either brake fade from overheating or a servo problem that leaves the brakes working but needing far more pedal force. This guide describes emergency technique for an event you hope never to meet. It is not a substitute for maintenance: a soft pedal, a sinking pedal, a brake warning light or a falling fluid level all mean stop driving now and get the car recovered.

Step by step

Press hard, and keep pressing.Do not lift off to try again in a panic. If the pedal is firm but the car is not slowing, push much harder than feels reasonable — a servo failure removes the assistance, not the brakes, and the force required is genuinely large.
Pump the pedal if it feels soft or long.A soft or sinking pedal suggests air or a partial hydraulic loss. Rapid firm pumps can build enough pressure in the working circuit to give you meaningful braking. This is one of the very few situations where pumping is right.
Lift off and change down through the gears.Engine braking is substantial and it is available immediately. Change down progressively rather than dropping several gears at once, which can lock the driven wheels. In an automatic, select a lower gear range or use the paddles if it has them.
Use the parking brake progressively.On a car with a cable handbrake, pull it up gradually with the button pressed in so you can release it instantly if the rear wheels lock. On a car with an electronic parking brake, most will apply a controlled emergency braking function if the switch is held while moving — the handbook says. Do not simply yank either type on.
Get everyone's attention.Hazard lights, headlights, and the horn. You are about to do something unpredictable and the drivers around you need warning. This costs nothing and buys space.
Steer for a way out rather than trying to stop where you are.An uphill slip road, a rising verge, a rough grass bank, a stretch of gravel. Gradient and rolling resistance scrub speed effectively and safely. Aim off the carriageway early rather than braking hopefully in a queue.
Use friction as a last resort, deliberately.Brushing a nearside barrier, a hedge or a bank at a shallow angle will slow the car and is vastly preferable to a head-on or a rear-end impact. Choose the softest thing available and take it at the shallowest angle you can.
Never switch the engine off while moving.It removes the power steering assistance and, on some cars, can lock the steering. You also lose the vacuum reserve and the engine braking. Keep it running until the car has stopped.
Do not drive it afterwards.Once stopped, that is where the car stays. Call recovery. Whatever caused it — fluid loss, a failed servo, boiled fluid, a seized caliper — needs a garage, and none of it is diagnosable at the roadside.

Common mistakes

Yanking the handbrake on hard at speed — It locks the rear wheels, which makes the car unstable and can spin it. Progressive application with the release button held in, so you can back it off instantly, is the technique.
Switching the engine off to stop the car — You lose power steering, engine braking and any remaining servo vacuum, and on some cars the steering can lock. Leave it running until you are stationary.

If it doesn't work

Pedal goes to the floor with no resistance

Cause: Hydraulic failure — a burst line, a failed master cylinder, or a major fluid loss — Fix: Pump hard and use gears and the parking brake. This is the genuine failure case and it is rare. Stop the car and have it recovered; do not attempt to move it again.

Pedal is rock hard and the car barely slows

Cause: Vacuum servo failure — often a split hose or a failed vacuum pump — Fix: The brakes work. Push with both feet if necessary. Many drivers report this as total failure because they have never applied that much force to a brake pedal.

Brakes faded after a long descent

Cause: Overheating — pads, discs or boiled fluid — Fix: Use engine braking and stop safely to let them cool. Prevent it by selecting a low gear at the top of a descent rather than riding the brakes down. Boiled fluid usually means the fluid is overdue for changing.

Accelerator stuck open at the same time

Cause: A jammed mat, a sticking cable or a throttle fault — Fix: Select neutral immediately — this disconnects the engine from the wheels and lets you brake normally. Do not switch off while moving. Once stopped and in neutral, then switch off.

Brakes work but the car pulls violently to one side

Cause: One circuit or one caliper has failed — Fix: Expect it and hold the wheel firmly with both hands. Brake in a straight line, gently, and get off the road.

Brake warning light came on and then the pedal changed

Cause: Fluid loss or a circuit failure developing — Fix: This is the warning that precedes the event. A brake warning light with a changed pedal feel means stop immediately and call recovery, not carry on to a garage.

Questions people ask

How likely is total brake failure?

Very unlikely on a maintained modern car. Dual-circuit hydraulics mean a single failure leaves braking on two wheels, and a warning light usually appears before anything is noticeable at the pedal. Almost all reported brake failures turn out to be servo failure or brake fade, in both of which the brakes still work.

Does an electronic parking brake work as an emergency brake?

On most cars, yes — holding the switch while moving triggers a controlled emergency stop through the ABS system rather than simply clamping the rear wheels, which is safer than a cable handbrake. The procedure is in the handbook and it is worth reading before you need it.

How do I stop the brakes overheating on a long descent?

Select a low gear at the top and let the engine do the retarding, using the brakes in firm short applications rather than continuous light pressure. Riding the brakes down a long hill is what boils the fluid and glazes the pads.