HYDRAULIC CLUTCH SYMPTOMS - BLEED AND DIAGNOSIS PROCEDURE

VEHICLES AFFECTED: 1985 'J' Series

The bleeding and diagnosis procedures for the hydraulic clutch were omitted from the 1985 'J' Series Service Manual.

BLEEDING HYDRAULIC SYSTEM

The process of removing air from the pipe line and cylinders is known as 'bleeding' and is necessary whenever any part of the system has been disconnected, or level of fluid in the reservoir has been allowed to go below the minimum level so that air has been drawn into the master cylinder.

NOTICE: Never, under any circumstances, use fluid which has been bled from a system to fill the reservoir a s it may be aerated, have too much moisture content and possibly be contaminated.

1. Clean dirt and grease from the cap to ensure no foreign substances enter the system.

2. Remove cap and diaphragm and fill reservoir to the top with approved brake fluid only. (Brake fluid must be certified to DOT 3 specification).

3. Full loosen bleed screw which is in the slave cylinder body next to the inlet connection.

4. Fluid will now begin to move from the master cylinder down the tube to the slave. It is important that for efficient gravity fill, the reservoir must be kept full at all times.

5. It will be noticeable at this point, that bubbles will appear at the bleed screw outlet. This means that air is being expelled. When the slave is full, a steady stream of fluid will come from the slave outlet. At this point, tighten bleed screw to a torque of 2 N.m.

6. Assemble diaphragm and cap to the reservoir, fluid in reservoir should be level with step.

7. The hydraulic system should now be fully bled and should release the clutch. Check vehicle by starting, pushing clutch to the floor and selecting reverse gear. There should be no grating of gears, if there is, the hydraulic system still contains air. If this is the case, repeat bleed procedure.

ON - VEHICLE SERVICE

CLUTCH HYDRAULIC SYSTEM

NOTICE: The clutch hydraulic system is serviced as a complete unit, it has been bled of air and filled with fluid. Individual components of the system are not available separately.

CLUTCH HYDRAULIC DIAGNOSIS

FAULT CAUSE ACTION ----- ----- ------ Pedal travels to floor. Master or slave cylinder Check components and No pressure or very faulty. Hose/ pipe burst replace. Then bleed little resistance. or leaking. Connections system. leaking. No fluid in reservoir.

Pedal travels to floor. Rear seal failure in master Service or replace No pressure or very little cylinder. unit. Then bleed resistance. Fluid in master system. cylinder dust cover.

Pedal travels to floor. No Master cylinder center Service or replace pressure or very little valve seal faulty. unit. Then bleed resistance. Fluid level in system. reservoir rises as pedal is depressed.

Fluid in ares of master Rear seal failure in Service or replace cylinder dust cover and master cylinder. unit. Then bleed on pedal. system.

Fluid in slave cylinder Slave cylinder plunger Service or replace and on cylinder body. seal faulty. unit. Then bleed system.

Pedal feels "spongy" when Air in system. Check fluid level. depressed. Bleed system. Check and replace parts if symptom recurs.

Pedal effort high with Incorrect size master Check and fit correct long pedal travel. or slave cylinder fitted. unit. Then bleed system.

Unable to select gears. Clutch mechanism faulty. Check and replace Pedal effort and travel Gearbox faulty. clutch or gear box normal. components.

Clutch slip. Clutch plate worn. Master Check and replace. and/or slave cylinder seal Clean and service or worn or damaged. Over- replace units. Remove filled reservoir. excess fluid.

Pedal effort and travel Clutch or gearbox mechanism Check and replace normal. Difficulty in faulty. Wear in clevis faulty or worn selecting gears. linkages. components.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.