Power Assisted Steering (PAS) Pump and Reservoir The PAS fluid pumps used on both the Td6 and V models are of the vane type and are similar in their operation. The pumps are driven by a polyvee belt from the engine crankshaft pulley. A tensioner is used to maintain the correct tension on the belt.
STEERING 57-20 DESCRIPTION AND OPERATION V8 PAS Pump and Reservoir 1 Cap 2 Reservoir 3 Reservoir mounting bracket 4 Engine mounting bracket 5 Pump assembly 6 Pulley 7 Screw M (2 off) 8 Bolt M (2 off) 9 Bracket The V PAS pump comprises a body which houses the internal components of the pump. A pressure relief valve, which also incorporates a flow control valve, is installed in the housing. The pressure relief valve limits the maximum pressure to between 124 and 132 bar (1800 and 1915 lbf/in 2 ). The flow control valve limits the maximum flow to between 9.75 and 11.25 l/min (2.14 and 2.47 UK gal/min). A shaft runs longitudinally through the pump. One end of the shaft has a drive flange which accepts the drive pulley. The opposite end is closed by a cover. The shaft runs in bearings located in the body. Oil seals at each end of the shaft prevent leakage. An oval cam ring is located in the body. Ten vanes are housed in a carrier and rotate within the cam ring. The carrier is mounted in the centre of the shaft and receives positive drive from the shaft via a drive pin. The carrier is seated against an end plate which is located in the cover. The front of the carrier is covered by a port plate which is located against a seal plate in the body. The port plate controls the fluid flow into and out of the vanes during their cycle. The fluid reservoir used on the V model is mounted remotely on the LH side of the engine compartment, adjacent to the engine coolant reservoir.