All Other Models

From a cold engine, disconnect vacuum amplifier-to-thermo valve vacuum tube. Disconnect No. 1 purge control valve-to-thermo valve vacuum tube from thermo valve (under intake manifold). Start engine and run at 2000 RPM (1500 RPM for GLC Wagon and 626). No vacuum should be felt at either port. See Fig 1.

Fig 1: Testing Water Thermo Valve (Exc. Mazda B2000 Models)
Courtesy of MAZDA MOTORS CORP.
Warm engine until coolant temperature is 131°F (55°C) on GLC, 138°F (59°C) on GLC Wagon or 114-129°F (46-54°C) on 626. With engine at proper temperature, vacuum should be felt. If valve does not respond as outlined, replace water thermo valve.

NOTE: Testing of Mazda 626 thermo switch is explained in "Mazda Piston Engine Air Pump Air Injection" article in this section.