DUSTER BRAKE PEDAL ISSUE
My 2017 Renault Duster has had a stubborn, apparently complex, braking problem since new. I have repeatedly tried to have the fault diagnosed, so far without success. The brake master cylinder has been replaced. I remember one of the CAR testers mentioning a similar problem with a Duster driven in 2017 and its brake pedal “travelled too far”.
Half the time, the brakes work normally (it helps to pump them before starting the car). During this phase, the brakes gently start to bite right from the top of the pedal stroke as per normal and are easy to modulate. Then, for some unknown reason, the pedal needs to travel a bit further from the top of its stroke. As it travels downward, the pedal starts to harden and the driver has to increase pedal pressure until the brakes suddenly bite, making the car lurch forward as if the brakes had been applied in an emergency.
According to the owner’s handbook, the vehicle is equipped with ABS and EBA with EBD for detecting an emergency braking situation. Do you think it’s possible that one of these systems is faulty? What course of action do you suggest I take? JOHN HOLTZHAUSEN Somerset West
We agree the braking feel should at least be constant and not vary as you described. Firstly, the vehicle is under warranty and the problem should be xed by a Renault dealer, especially if it behaves differently to other Dusters of similar vintage. CAR ran the previous and current Dusters as part of its long-term eet and we never experienced such variance on pedal feel and performance.
Factors in uencing pressure build-up and pedal travel are: • Brake uid level – if too low, air
will enter the system.
• Brake master cylinder – when the seals start to leak, pressure will struggle to build.
• Brake booster – if not functioning as normal, the assistance of force on the pedal will vary. • Leak – may lead to loss of brake
uid and air into the system. • An ABS fault resulting in varying pedal behaviour. We assume the dealer performed a diagnostic check on the ABS pump to rule out faults. The master cylinder was replaced and a leak or low brake- uid level would have been picked up. This leaves the brake vacuum booster. Request that the dealer investigate the complete booster system with a focus on the vacuum pump (if a diesel model), piping and booster itself. Pumping the brake when the engine has not started bypasses the assistance from the booster and this may explain why it helps to pump the brake before starting.