Brake Fluid Equalizer

[Max Hoepli]

Hi all,

Just had the original brake fluid equalizer/proportioner [C$355] changed. Found in front of the left rear wheel.
Anyone know what the equalizer has inside? Mechanic says equalizer was seized, practically only the front brakes were working. Anyone can give some knowledge of the function of the equalizer? The car with the old equalizer was making boing-boing spring noises at the back, most noticeable in an underground garage. With the new equalizer very smooth, quiet boingless braking.
The rotors in the back were rough, rusty on the inner surfaces. only the outer surfaces were touched by disc pads. 

Should the mechanic 3 weeks earlier who changed the front brake shoes C$135 and both front rotors, each C$140 have noticed that the equalizer was defective? The car was making rubbling noises when the brakes were applied after this service, with time I was aware that this noise was coming from the back, which prompted me to see my other mechanic.

There has never been discussion of the brake fluid equalizer as far as I know in this group.
It seems to me it might be a good idea to grease the shoulder joint of an equalizer to prolong its life.

Max
1986 Quattro type 44