I have a slight hissing coming from around the brake pedal area when engine is running. It stops when I put slight pressure on the foot on brake, so after reading the service manual I’m guessing there is a vacuum leak in the servo on the back part of the diaphragms. The servo is a Dunlop with a split clamp so I presume it can be taken apart. Has anyone rebuilt one of these and if so is there a service kit you can get??
I have a feeling it the lip seal on the back part that’s leaking …