Except Federal 4WD
- With engine coolant below 122°F (50°C), remove hose leading to thermo vacuum valve from vacuum switching valve (VSV). Blow air into hose toward thermo vacuum valve and check that air flow is blocked.
- Start engine and warm coolant above 147°F (64°C). Again blow air into hose toward thermo vacuum valve and check that air flows through valve. Replace thermo vacuum valve if it does not operate as outlined.