Thermo valves are used on feedback carburetor equipped vehicles only. Multi-point fuel injection equipped vehicles use the ECU to activate the purge control solenoid valve. The valve, which is incorporated in the EGR system, is used for sensing the coolant temperature at the intake manifold. It closes the purge control valve when the coolant temperature is lower than a preset value, its function is to reduce CO and HC emissions under warm up conditions and to open the purge control valve when the coolant temperature rises above the preset temperature.
See Figures 1
When removing and installing the thermo valve, do not attempt to loosen the resin portion of the valve with a wrench. When disconnecting the vacuum hoses, make sure they are labeled for proper reassembly.
- Disconnect vacuum hose A from its nipple on the valve.
- Connect a suitable hand vacuum pump to nipple A and apply vacuum to the valve.
- At engine coolant temperatures below 56-66°deg;F (13-19°deg;C), the valve should not hold vacuum. At temperatures above 60-68°deg;F (16-20°deg;C), the valve should hold vacuum.
- Disconnect the remaining 3 hoses from the valve.
- Connect the vacuum pump to either nipple B, C or D of the valve. Plug the valve nipples that are not being used. Apply a vacuum to the nipple.
- At engine coolant temperatures below 140-150°deg;F (60-66°deg;C), the valve should not hold vacuum. At temperatures above 145-153°deg;F (63-67°deg;C), the valve should hold vacuum.
- If the valve does not function as described, replace the valve.