Component Description

EGR VALVE
The EGR valve is mounted on the intake manifold and controls exhaust gas flow into the intake manifold. The vacuum diaphragm chamber is connected to the carburetor flange vacuum port through the thermal vacuum valve. Opening the throttle valve applies a vacuum to the vacuum diaphragm. When the vacuum reaches a predetermined value, the diaphragm overcomes spring tension and moves to its fully raised position. The upward motion of the diaphragm opens the EGR valves allowing exhaust gas to be drawn into the engine intake system.

THERMAL VACUUM VALVE (TVV)
The TVV is mounted on the intake manifold and is connected in series with the carburetor vacuum port and EGR valve. Valve operation is provided by a bi-metal switch. The valve remains closed and the EGR system does not operate as long as the coolant temperature remains below a predetermined value. As coolant temperature rises above the predetermined value, the valve will open and the EGR system will begin to operate.