TM 5-3805-258-24-1
A I R S Y S T E M A N D B R A K E S
T E S T I N G A N D A D J U S T I N G
HOT OR DRAGGING BRAKES
T o o l s N e e d e d : 0 t o 1 3 8 0 k P a ( 0 t o 2 0 0 p s i ) G a u g e .
6 . 4 m m ( . 2 5 i n . ) d i a m e t e r b y 1 5 0 mm
( 6 i n . ) l o n g b o l t .
Hot or dragging brakes are caused when the
brakes do not release correctly. When the stroke
of the master cylinder is too much, the brake fluid
pressure indicator, master fault light and fault
alarm will come ON. Brake hydraulic pressure is
16 times the amount of air pressure.
WARNING
Make reference to WARNING on first page of
AIR SYSTEM AND BRAKES TESTING AND AD-
JUSTING section.
Use the procedure that follows to correct a prob-
lem of hot or dragging brakes:
L O C A T I O N T O I N S T A L L G A U GE
1. Drain valve for the air reservoir.
NOTE: If the brake fluid pressure indicator is on, go
to Step 9b.
1. Install a 0 to 1380 kPa (0 to 200 psi) gauge in
drain valve (1) of the air reservoir.
2. Remove brake fluid pressure switch (2), and
the indicator rod from the air/hydraulic cyl-
inder. Use a 6.4 mm (.25 in.) diameter bolt
that is 150 mm (6 in.) long, in place of the in-
dicator rod.
NOTE: Two bolts can be used to check both master
cylinders at the same time.
A I R / H Y D R A U L I C C Y L I N D E RS
2. Brake fluid pressure switch for rear wheel brakes. 3.
Brake fluid pressure switch for front wheel brakes (under
b r a c k e t ) .
3. Start the engine and let the air pressure go up to
cutout pressure. Stop the engine. (See Chart,
page 4-60).
NOTE: Make sure air pressure is above 620 kPa
(90 psi) when the master cylinder stroke is checked.
4.
5.
6.
7.
8.
9.
I N D I C A T O R R O D R E M O V E D A ND
6 . 4 m m ( . 2 5 i n . ) B O L T I N S T A L L E D
4.150 mm (6 in.) bolt.
With the brake fully released, push bolt (4)
down until it comes in contact with the piston
in the air chamber.
Measure the length of the rod.
Push and hold the right brake pedal down.
Push bolt (4) down again, until it comes in
contact with the piston.
Measure the length of the rod at this point.
The difference in the two lengths is the stroke
of the master cylinder.
4-64
