740 & 760 Brakes dragging - master cylinder?
Car is a 1990 740GL sedan with Bendix twin piston calipers at the front and ATE at the rear and ABS.
All four wheels are difficult to turn by hand. The front wheels are slightly harder than the rears but the difference is minimal. As the wheels are rotated there is a definite hard-rubbing sound from the brake pads.
I have tried removing the brake pads and the wheels then turn freely. I had a lot of difficulty retracting the pistons on the front calipers as there was a lot of resistance.
Since this is affecting all four wheels could this be the master cylinder at fault? Is there a way I could test if it is the master cylinder? The brakes seem to operate fine, this car has always had good brakes. The pedal doesn't sink to the floor.
It had new pads and discs on the front about a year ago and new brake hoses about 2 years ago. New pads on the back a couple of years ago, rear rotors are fine. It's just about due for a brake fluid flush but I doubt that the fluid itself could be the cause.
Thanks for any advice.