Mazda RX-8 Workshop Manual page 2566

3. Connect the vacuum pump hose to the center joint of the manifold gauge.
4. Connect the vacuum pump hose to the vacuum pump.
5. Connect the charging hose to the refrigerant tank.
6. Place the refrigerant tank on the scale.
7. Open all the valves of the manifold gauge.
CAUTION:
Close the manifold gauge valve immediately after stopping the vacuum pump.
If the valve is left open, the vacuum pump oil will back flow into the
refrigeration cycle and cause a decrease in the efficiency of the air conditioner.
8. Start the vacuum pump and let it operate for 15 min.
9. Verify that high– and low–pressure side readings of the manifold gauge are at –101 kPa {–
760 mmHg, –29.9 inHg}. Close each valve of the manifold gauge.
10. Stop the vacuum pump and wait for 5 min.
11. Inspect the high– and low–pressure side readings of the manifold gauge.
If the reading has changed, inspect for leakage and then repeat from Step 7.