1979 Models

Drain engine coolant and remove thermal vacuum valve from engine. Submerge valve in a container of water. See Fig 1. Apply vacuum to top port of valve and check that valve opens and closes according to water temperature specified in THERMAL VACUUM VALVE TEST SPECIFICATIONS table. If not, replace thermal vacuum valve.

NOTE: A 3-port thermal vacuum valve may be used on some models. The bottom port of the 3-port valve is used with the Transmission Controlled Spark system.

THERMAL VACUUM VALVE TEST SPECIFICATIONS

Application

Valve Closed
°F (°C)

Valve Open
°F (°C)

210 & 310

2-Port Valve

Below 104 (40)

Above 145 (63)

3-Port Valve

Below 122 (50

Above 145 (63)

280ZX & 810

⁽¹⁾

⁽²⁾

All Others

Below 104 (40)

Above 127 (53)

⁽¹⁾	Below 117°F (47°C) and above 208°F (98°C).

⁽²⁾	Between 122°F (50°C) and 203°F (95°C).

Fig 1: Thermal Vacuum Valve Test (2-Port Valve)

Courtesy of NISSAN NORTH AMERICA, INC.