SWING BRAKE VALVES
SWING BRAKE VALVES
to the brake circuit. Since the oil in the brake circuit was
SWING BRAKE VALVE (36Q45)
vented to tank when the brake pedal was depressed, a pres-
sure differential exists on each side of the check valve. This
pressure differential allows the oil at the pressure port to
lift the check valve from its seat, and flow into the brake
Swing brake valve 36Q45 is operated by the swing brake
circuit. When the pressure in the brake circuit equals the
pedal in the upper cab, and is used to control the operation
pressure at the pressure port, the check valve spring will
of the swing brake. The operation of the valve is as follows
seat the check valve and the brake will be maintained in the
released position until the brake pedal is again depressed.
To remove the swing brake valve, proceed as follows:
1. Depress and hold the brake pedal for several seconds to
vent trapped pressure from the brake circuit.
2. Loosen the brake port connections, but do not remove
the fitting nut completely. Tap the tube gently to ensure
that the oil tight connection is broken. This will allow any
pressure which might still be trapped in the brake circuit
3. Disconnect the pressure, tank and brake port tubes from
Figure 6F-1. Swing Brake Valve (36Q45)
the valve. Cap the tubes to prevent the entry of dirt into
When the brake pedal is in the released position, hydraulic
pressure in the swing brake circuit is prevented from re-
4. Disconnect the brake pedal linkage from the valve spool.
turning to tank by the check valve in the valve body. This
Remove the capscrews and washers which secure the valve
trapped pressure will maintain the swing brake in the re-
to the cab floor, and remove the valve.
leased position until the swing brake pedal is depressed.
When the brake pedal is depressed, the valve spool is pulled
outward from the valve body. The outward movement of
GENERAL. All parts in this valve are replaceable sepa-
the valve spool will first block the pressure port, and then
rately, with the exception of the valve body and spool
lift the check valve off its seat and open the tank port.
which must be replaced as a unit. It is recommended, how-
Lifting the check valve off its seat, allows the oil in the
ever, that the complete valve assembly be replaced when the
brake circuit to return to tank, thereby allowing the brake
spool or body are no longer serviceable.
springs to apply the swing brake.
DISASSEMBLY. If the valve is to be overhauled, use the
When the brake pedal is returned to the released position.
the valve spool moves into the valve body. Inward move-
ment of the valve spool blocks the tank port first, and then
allows the check valve to seat and opens the pressure port
1. Clamp the valve in a vise with the brake port up. Use