W123-ADS, -3ADS Revision 3
9)
Brake fluid and bleeding the system
a)
After completing all hydraulic connections, install new brake fluid (at master cylinder
reservoir). Remove the master cylinder and bench bleed the master cylinder. Pump
brake pedal several times to initially fill the system and advance the caliper pistons to
their working position.
WHEN BLEEDING THE SYSTEM, PUMP FLUID SLOWLY INTO THE NEW
SYSTEM. IF FLUID “FOAMS”, IT WILL TAKE A LOT OF FLUID TO BLEED THE
BRAKES. SOFT PEDAL IS A RESULT OF POOR BLEEDING. TAKE YOUR TIME!
9A)
Bleeding the system
a)
When pressure bleeding is employed the correct pressure setting is 10-15 psi. (max.)
for the bleeder tank.
b)
If power brakes are fitted, the engine should not be running and the vacuum reserve
should be reduced to zero by pumping the brake pedal or pulling the booster vacuum
hose.
c)
Tapping the caliper with a rawhide mallet, before fluid is flowing, may assist in
obtaining a better bleed job.
d)
Brake bleeding can be simplified by assuring that there are no line restrictions, by
using the gravity bleed approach as follows:
1)
Leave all bleeder screws open when installing calipers.
2)
Fill master cylinder reservoir, do not pressurize master cylinder or pump brake
pedal; instead observe bleeder ports until brake fluid flows out; then shut
bleeder valves.
3)
No further procedure is required if brake pedal is hard after shutting off all
bleeder valves. Make sure that the master cylinder is "topped-off."
e)
With bleeders closed and system bled, a hard pedal should be experienced so that at
full application and with the engine running, the toe of your left foot can still be placed
between the bottom of the pedal and the floor.
1)
In addition there should be brake pedal end-play of 3/4 to 1" inch (from full
release until initial braking action takes place).
2)
Power brake cars will experience a "drop-off" of the pedal when the engine is
started. This is a normal condition, and signifies that the booster is working
correctly.
DO NOT DRIVE THE CAR UNTIL THE BRAKES STOP THE CAR SAFELY,
INITIAL BRAKING TESTS SHOULD BE DONE IN A SAFE OPEN AREA! LOOK
FOR LEAKS AND INTERFERENCES!
f)
If brake pedal "end-play" is excessive, adjust push-rod between the brake pedal
and booster (to lengthen) in 1/4 turn increments until 1" of "end-play" is
achieved.
11)
Final inspection
4