Rear brake bleeding noise

[Dattebayo]

When I bleed the rear brakes a strange noise emanates from underneath the car I have a hard time describing... It sounds like a squeaking or something high pitched, but it only happens when I release the bleeder screw pressure. It goes away when the pedal bottoms out. So yeah, pretty much only when bleeding. Thoughts?

[MaximA32]

Could just be the brake master cylinder making a noise or it could be the brake booster. Have you checked out either of those?

[Dattebayo]

Could just be the brake master cylinder making a noise or it could be the brake booster. Have you checked out either of those?

The noise comes from the rear under the car. It happens ONLY when the bleeder is turned with someone putting pressure on the pedal and it's not from the bleeder it's self.

[MaximA32]

Could be a proportioning valve that splits the brake line coming back into 2 going to the rear wheels.

[Dattebayo]

Proportioning valve is on the firewall behind the intake manifold.

I wonder if the two problems are related? See my other thread...