Circuit ISUZU TFS SERIES 1997 Workshop Manual

BRAKES 5-21
Operation
The operation of the P-valve by the master cylinder
pressure is unchanged up to the brake points
A and B.
If master cylinder fluid pressure penetrates into the second
break point
B, the fluid pressure pressing against the seal
2, (which isolated route 4 and route 5), passing the route
4 of the master cylinder side, overcomes the operating
force of the spring
3 + fluid pressure affecting the seal 2 of
the wheel cylinder, and presses the piston
1 to the right
side, resulting in the opening of the routes
4 and 5, and
canceling of the P-valve operation.
Then, because the master cylinder fluid pressure and the
wheel cylinder fluid pressure, up to the point
C, operate on
the identical surface of the seal
2, both have identical
ascending ratio.
However, because of the operation of spring
3 in the wheel
cylinder side, wheel cylinder fluid pressure operate to
preserve the balance against the master cylinder fluid
pressure on the lower level with the difference in pressure
resulting from this spring.
Valve Maintenance
In the case of fluid leak or other abnormalities, faulty valve
should be replaced.
The valve is set up at the right hand side of the 5th
crossmember near the rear axle.
Note:
The blend proportioning valve is not repairable and must
be replaced as a complete assembly.
BLEEDING OF THE BRAKE HYDRAULIC
CIRCUIT
If air enters the bake lines, it will cause poor brake action.
Therefore, bleeding should be performed if the brakes have
been used with the level of brake fluid in the reservoir
excessively low or if brake pipes have been disconnected in
the course of brake servicing.
Bleeding operation calls for co-operative action of 2 persons.
Set the parking brake firmly while bleeding.
Perform bleeding operation with ENGINE RUNNING, to
prevent damage to push rod seal.
Make sure exhaust is suitably ventilated.
Bleed the hydraulic system with the fluid reservoir filled to
the specified level.
Bleed the system starting with the rear wheel cylinder
farthest from the master cylinder.
A : Load sensing proportioning valve (If so equipped).

BRAKES 5-67
TROUBLESHOOTING
Condition and Cause Correction
Poor Brake Action
Master cylinder faulty Correct or replace
Power cylinder faulty Correct or replace
Level of brake fluid in reservoir too low Replenish and bleed
Air in hydraulic circuit Bleed
Front disc brake caliper faulty Clean or replace
Rear brake wheel cylinder faulty Clean or replace
Water or oil on brake pads or linings Clean or replace
Brake pads or linings hardened Replace
Brake pads or linings in poor contact with rotor or brake drum Correct
Brake pads or linings worn Replace
Brake disc or drum rusted Grind or replace
Check valve in vacuum hose faulty Correct or replace
Brake Squeak
Brake pads or linings worn Replace
Brake pads or linings hardened Replace
Brake pads or linings in poor contact with rotor or brake drum Correct
Brake disc(s) warped, worn or damaged Grind or replace
Disc brake anti-squeak shims fatigued Replace
Front hub bearings loose or preload is incorrect Adjust or replace
Brake disc or drum rusted Grind or replace
Brake Pull
Tire inflation pressures unequal Adjust
Front wheel alignment incorrect Adjust
Water or oil on brake pads or linings Clean or replace
Brake pads or linings hardened Replace
Brake pads or linings worn excessively Replace
Brake drum or rotor worn or scored Grind or replace
Front or rear wheel cylinder or disc brake caliper malfunctioning Clean or replace
Front hub bearing preload incorrect Adjust or replace
Brake pad or lining clearances unequal Adjust or replace
Brake Drag
Parking brake maladjusted Adjust
Brake pad or lining clearance insufficient Adjust
Brake pedal free play insufficient Adjust brake pedal height or power cylinder operating rod
Piston in master cylinder sticking Clean or replace
Pistons in disc brake caliper sticking Replace piston seals
Pistons in rear brake wheel cylinders sticking Clean or replace
Brake pads sticking in caliper Clean
Return springs weakened Replace
Parking brake binding Overhaul rear brakes
Front hub bearing preload incorrect Adjust or replace
Rear brake shoes not returning Correct or replace brake back plate, check automatic adjuster and
replace as necessary
Obstructions in hydraulic circuit Clean
Rotor warped excessively Grind or replace
Rear brake drum distorted Grind or replace
Piston cups swollen Replace brake fluid and piston cups
Check valve ; vacuum hose faulty Replace
Parking cable sticking Clean or replace
Rear disc brake over adjust Adjust or overhaul rear brakes
Excessive Brake Pedal Travel
Air in hydraulic circuit Bleed hydraulic circuit
Level of brake fluid in reservoir too low Replenish brake fluid reservoir to specified level and bleed hydraulic
circuit as necessary.
Master cylinder push rod clearance excessive Adjust
Leakage in hydraulic system Correct or replace defective parts
Rear disc brake autoadjuster malfunction Overhaul rear brakes

7C-44 CLUTCH
2. CLUTCH DOES NOT RELEASE PROPERLY
Checkpoint Trouble Cause Countermeasure
Driven plateReplace the driven plate
Adjust the push rod play
Driven plate warped or
unevenly worn
Too much push rod play in the
slave cylinder
Hydraulic circuitBleed the hydraulic circuit
Adjust the push rod play
Air in the hydraulic circuit
Too much push rod play in the
master cylinder
OK
NG NG NG NG
OKClutch pedal free play
Clean or repair the top gear
shaft spline
Replace the top gear shaft
Corrosion or step wear on the
top gear shaft spline
Pressure plateReplace the pressure plate
assembly
Clean and grease the splined
contact surface
Pressure plate unevenly worn
Insufficient grease on the
spline contact surface of the
splined hub
OKNG NG NG
OK
Continued on the next page