Ninety-Eight FWD V6-181 3.0L (1985)
Thermal Vacuum Valve: Testing and Inspection
EGR Thermal Vacuum Switch (EGR-TVS)
Hot Check
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. 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 vacuum source hose from switch and connect hose to vacuum gauge, then repeat step 2.
5.
If vacuum gauge responds to throttle opening, the EGR-TVS is defective and should be replaced.
6.
If gauge does not respond to throttle opening, then check for obstructed hoses, fittings, etc.
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 vacuum source 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 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. Leakage of up to 2 inches Hg vacuum in 2 minutes is acceptable.
