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protection valve maintains air in the tractor brake system in the event of the trailer air lines becoming compromised.for example, if a trailer line is leaking, broken or disconnected
Off.
Run the motor to air up the air system. Once this is done, cut off the motor. With the motor off, put the vehicle into gear. Then, you push in the tractor protection valve, which will release the spring brakes. You then pump the brake pedal (or the Johnson bar, if you prefer) repeatedly, and this will bleed out air pressure. When the air pressure gets low (below 60), the tractor protection valve should pop out automatically.
With the vehicle aired up, push in the clutch, put the vehicle into gear, and turn off the ignition (leaving the tractor protection valve pushed in). When the motor is shut off, release the clutch. The motor will be off and the vehicle will be in gear, which will prevent you from rolling. Now, you simply pump on the brake pedal. This will reduce air pressure in the tanks (which won't build back up, as the motor is cut off). The tractor protection valve should pop out automatically when air pressure gets below 60.
Turn on the motor and let the air system charge. Put the vehicle into gear and keep your foot on the clutch. Turn the motor off and let your foot off the clutch once the motor has stopped turning. Turn the key to the 'on' position. Push in the tractor protection valve. Pump the brakes repeatedly. Once the air pressure drops to around 60, the low air warning light will come on. Continue pumping on the brake, and the tractor protection valve should pop out shortly afterwards.
Turn on the motor and let the air system charge. Put the vehicle into gear and keep your foot on the clutch. Turn the motor off and let your foot off the clutch once the motor has stopped turning. Turn the key to the 'on' position. Push in the tractor protection valve. Pump the brakes repeatedly. Once the air pressure drops to around 60, the low air warning light will come on. Continue pumping on the brake, and the tractor protection valve should pop out shortly afterwards.
If it's an on-road vehicle manufactured during or after 1975, then yes, it must. It must also have a dual circuit air system, in accordance with FMVSS 121. On a related note, a lot of drivers seem to think the tractor protection valve is the valve which releases the spring brakes on the power unit, and pokes through the dash with a (usually) yellow knob - it is not; that is the brake control valve, which must also be present.
Charge the trailer air brake system and check that the trailer rolls freely then stop and pull out the trailer air supply control also called tractor protection valve control the trailer emergency valve or place it in with the tractor to check that the trailer emergency brakes are on.
left atrioventricular valve and left mitral valve
MV3 valve is specifically a Bendix product. It's basically the (tractor) brake control valve and trailer supply valve in one housing.
Yellow for the tractor brake control valve, red for the trailer supply valve.
EGR Valve