S 420 (140.043) V8-4.2L (119.981) (1996)
8. Detach rotor (7) from the drive shaft (11) with a plastic-headed hammer and take off together with the vanes (10 off). Check the vanes (16) in the
grooves of the rotor (7); they must slide easily in the rotor.
Check sliding face of vanes at cam insert for signs of wear. If necessary, repair steering pump by using the "Pump insert" repair kit.
9. Take off thrust washer (5).
NOTE: On tandem pumps (1st version) no thrust washer (5) is fitted. If, on these tandem pumps, it is found that the drive shaft does not move
freely,is seized or fractured, the tandem pump must be replaced.
10. Number screw cartridges (40) consecutively from 1-4, then unscrew all 4 screw cartridges (40) from the housing with the pin wrench (010) part
no. 129 589 02 07 00.
11. Check seals (39), replace if necessary. Take piston (37) and spring (38) out of the screw cartridge (40). Examine piston and piston track for signs
of damage and wear. It must be possible to move the piston in the screw cartridge (40) easily and without it jamming. If this is not the case. replace
the screw cartridge.