With the suspicions of missing or malfunctioning relief please keep in mind that overpressured gauges can blow as well. For safety you need a small restrictor in the gauge line. I have done this by threading an appropriate sized set screw into the input end of the hose crimp ID....[the minumum size where your tap will grab]. The hole is tapped in the direction of flow and setscrew is stopped by the bottom of the threaded region so it cant unscrew. The oil is restricted by the helix to just a drop or three a second on the output where your gauge is. Once the line is filled with oil the pressure reads fairly quick -- several seconds cold to about a second hot.... and safe if the gauge blows.
larry
