A Brake Servo problem? Engine stalls on braking.

[TRTerry]

A brake servo problem?

The engine falters, then stalls on braking. It's not the lights draining on the battery. I can hear a hiss from the servo when the brake pedal is depressed. The hiss is slight on a partially depressed pedal and louder on a fully depressed pedal like a 'sshh' and you can hear the engine note change to lower revs then die. I have never noticed a hiss before, but I don't normally have the bonnet up while pressing the brake pedal, so don't know if this is normal. The brake pedal moves freely on its shaft.

Any ideas?

[bmcecosse]

Idle too slow? The servo uses air pressure - so yes there will be a bit of a hiss - but it's not usually noticeable. Has the problem just started - or is it ongoing?

[TRTerry]

It was the servo!

Upon inspection it had a 5cm gash in the large rubber diaphragm. Replaced and brake feel now as good as new. Can even lockup the wheels using forceful pedal pressure now.

[bmcecosse]

If the brakes are working as they should be - the wheels should lock WITHOUT a servo...........