TOOL 6V4145 - Caterpillar

The Retarder Air Control Valve is in the ON Position
Illustration 5 g00911593
(1) Air compressor governor (2) Air compressor (3) Air dryer (4) Air pressure relief valve (5) One-way check valve (6) Service air reservoirs (7) Drain valve (8) Diverter valve (9) Relay valve for rear wheel brakes (12) Double check valve (16) Pressure protection valve (17) Retarder brake control valve (19) Service brake control valve (23) Rear brake master cylinder (26) Secondary air reservoir (A) Air pressure switch for the retarder brake indicator (C) Air pressure switch (stop lamp for rear brakes) (E) Air pressure switch (F) Sensor for brake air pressure (G) Standard air lines (H) Air lines for the automatic retarder control (ARC) valve and for the air startNote: Darkened lines show air pressure and arrows show the direction of flow.Note: Air pressure switch (A), air pressure switch (C), air pressure switch (E) and sensor (F) are activated.When the engine is started, the air flow from air compressor (2) flows to air dryer (3). From air dryer (3), the air flows to one-way check valve (5) then into service air reservoirs (6). When the pressure in service air reservoirs (6) reaches 550 kPa (80 psi) pressure protection valve (16) will open. The air pressure will then flow to secondary air reservoir (26) through the one-way check valve (5) .When the air pressure in all of the air reservoirs reaches 830 kPa (120 psi), air compressor governor (1) will control the system pressure. An air pressure gauge in the cab will indicate the air pressure in the system. If the air pressure in the system falls below 483 kPa (70 psi), the needle on the brake air pressure gauge will be in the red area. The master action light will come on and the master action alarm will sound.Air pressure from service air reservoirs (6) will flow through the supply junction of service brake control valve (19). When the handle on retarder brake control valve (17) is moved to the ON, pressure air will flow through the retarder brake control valve. This air then flows through double check valve (12) to the control passage in relay valve (9) for rear wheel brakes.Air pressure to the control passage in relay valve (9) will cause an internal valve inside the relay valve to open. Supply air from service air reservoirs (6) will flow through relay valve (9) to the air chamber in rear brake master cylinder (23). Oil pressure from rear brake master cylinder (23) flows into the slack adjuster. The oil then flows to the rear brake housing and the rear wheel brakes will be applied. Engine speed must remain between 1500 rpm and 1900 rpm in order to keep the brake oil cool.
Do not increase machine speed while the pulled unit brake is ON.
Relay valve (9) also routes some air to the control passage of diverter valve (8). The air pressure to the control passage of diverter valve (8) causes oil that is flowing to the plates and