Screeching sound when pressing the brake pedal


Well-known member
Hi all,

This happened twice in two days, after starting the car the first time in the day (ambient +-34C).


It doesn't happen after driving around and then starting the car again.

I went past my mech yesterday, and he tightened the bolts on the brake booster. They were not loose, but there was some give in them.

Funnily enough, I saw the replies to my question on another two forums, and got similar feedback. Someone posted this TSB, which affects the booster, it may be helpful to others:

"Reference: SSM72903
Models: Range Rover/ L405 Range Rover Sport/ L494
Title: Air Leak Noise When Brake Pedal Is Pressed
Category: Chassis
Last modified: 29-Jul-2016 00:00:00
Symptom: 301000 Service Brake System
Attachments: D7u Booster Fixings Secure Sequence.pdf (D7u Booster Fixings Secure Sequence.pdf)

Air-leak noise when brake pedal is pressed.

Low or high clamp load on brake servo fixings.

If an air-leak noise is exhibited during brake pedal depression, then slacken the 4 fixings off and re-torque to 24Nm. Ensure when torquing you follow the pattern detailed in the

Re-apply the torque (following the attached pattern) a second time 30 minutes later to ensure the fixings have not relaxed.

If the noise is still present then please progress with replacement of the component."



Well-known member
Ok, so the noise was present again today, so it looks like the brake booster needs to be replaced.

Although I've seen posts from others where they have had the noise for years with no ill effects, so...


I had that noise on a Jeep a long time ago. The diaphragm in the booster gets a pinhole in it and creates the noise. The amount of vacuum that can be pulled through such a pinhole is small, but the noise is not. Your brakes will probably work well for a while, but I'd go ahead and replace it if it were me because I like everything in my brake system to be up to spec and because that noise would take about 3 seconds to drive me completely and utterly insane.