Firebird V8-305 5.0L (1982)
Thermal Vacuum Valve: Testing and Inspection
EGR-TVS
COLD CHECK
1. Drain engine coolant below level of switch.
2. Disconnect vacuum lines and remove switch from thermostat housing.
3. Connect a vacuum gauge to "EGR" port and a hand held vacuum pump to "CARB" port of switch.
4. Place switch in water that is below the calibration temperature of the switch, and submerge for two minutes while agitating water.
5. Apply 12 inches Hg vacuum to "CARB" port and observe vacuum gauge. The switch should be closed and hold vacuum.
6. If operation of switch is not as specified, it should be replaced.
NOTE: Leakage of up to 2 inches Hg vacuum in 2 minutes is acceptable.
HOT CHECK
NOTE: The EGR-TVS should be open when coolant temperature is above the calibrated switching point, permitting ported vacuum to reach the
EGR valve.
1. Disconnect hose from EGR valve and connect a vacuum gauge to hose.
2. Start engine and partially open throttle. As throttle is opened, the vacuum gauge should respond with an increase in vacuum.
NOTE: Engine coolant temperature must be above the calibration temperature.
3. If operation is as specified, remove gauge and reconnect hose to EGR valve.If operation was not as specified, proceed to step 4.
4. Remove Carb-to-Switch hose from switch and connect hose to vacuum gauge, then repeat Step 2.
5. If vacuum gauge responds to throttle opening, the EGR-TV is defective and should be replaced.
6. If gauge does not respond to throttle opening, then check for obstructed hoses, fittings or defective carburetor.
NOTE: Refer to the number stamped on the base of the switch or valve for calibrated switching or activation temperatures.
