1. Not enough oil in the tank 2. Clogged filters on the suction hydraulic lines of the pumps 3. Jammed and pinched sections of the hydraulic lines
1. Check the oil level in the tank and, if necessary, top up 2. Check the readings of the vacuum gauges on the filters when the engine is in steady state and the oil in the system is warm. The arrows should not be in the red sector, exceeding the value of 0.2 bar. Replace if necessary