Open all valves while pumping down. (The port valves are opened by turning clockwise). Leave port valves open, close high & low valves on manifold, turn off vac pump in that order. Observe vacuum on gauges. It should hold steady. If it drops you've got a leak. Technically you only need to open one side, either high or low, to evacuate since it's one looped system, but most techs prefer to open both.

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82 300SD 202K
82 300SD 233K
83 300TD 340K
82 300TD 98k euro (parts on the hoof)
85 300TD 282K
83 300TD 197K