Subaru LEGACY 2002 Quick Reference Index page 432

Brakes
A: PRESSURE HOLD VALVE (PHV)
! The PHV is located on the piping that connects the master cylinder and the ABS control module/
hydraulic control unit. It has a camshaft which turns either way by rotation of the lever which is
linked to the clutch pedal. The cam of the crankshaft allows the pushrod in the PHV to move right-
ward (in the drawing below) under the force of a spring when the clutch pedal is depressed and
pushes it leftward against the force of the spring when the clutch pedal is released. At the left of
the pushrod, there is a ball housed in a chamber which has a seat for the ball. When the vehicle
is on a level road, this ball stays at the left (front) of the chamber, but on an uphill road, it tends to
move rightward by the gravity. In the latter case, the ball makes contact with the seat unless it is
forced to leave the seat by a leftward movement of the pushrod (resulting from release of the clutch
pedal).
! When the vehicle is stopped on an uphill road, the driver depresses both the brake and clutch
pedals. In this condition, the ball is in the rear (right) position, making contact with its seat and pre-
venting flow of the brake fluid toward the master cylinder. The driver then release the brake pedal
while keeping the clutch pedal depressed to restart the vehicle. The brakes, however, remains ap-
plied because the pressure in the line to the wheel cylinders is kept unreleased. Then, the driver
can release the clutch pedal in the same way as with on a level road while depressing the accel-
erator pedal since the release of the clutch pedal causes the pushrod to push the ball away from
its seat and the brakes are released.
(1) Body
(2) Camshaft
(3) Ball
(4) Ball guide
(5) Seal
HILL HOLDER
(6) Plate spring
(7) Cap
(8) Pushrod
(9) Spring
(10) Boot
BR-12
(11) Cover
(12) Lever
(13) O-ring
(14) O-ring
B4H1937A