1. Remove the oil pump from the vehicle (see "Removal and installation the oil pump").
2. Drain the oil from the pump.
3. Remove the five screws securing the oil pump cover...
4. ...and remove the cover.
5. Remove the pressure reducing valve spring retainer.
Warning: The pressure reducing valve spring is installed with tension. To avoid the spring "shooting" and causing injury, remove the retainer very carefully and hold the spring stop.
6. Remove the spring stop...
7. ...spring...
8. ...and the plunger of the pressure reducing valve.
9. Measure the radial clearance between the gears and the pump body. It should be 0.110-0.249 mm.
10. Measure the axial clearance of the gears. It should be 0.020-0.086 mm. If the measured clearances do not correspond to the permissible values, replace the housing or the pump assembly.
11. Wash the pump body and dismantled parts from dirt and deposits. Remove dense varnish deposits from the internal cavities of the pump, having softened them with a solvent beforehand.
Helpful advice: Varnish oil deposits are easily removed with commercially available engine flushing products (so-called "five-minute" products).
12. Inspect the pump body and cover. If there are cracks, scratches, casting defects, damaged threaded holes, replace the body (because it is not repairable) or the pump assembly.
13. Check the relief valve plunger for scratches and signs of seizure. Small dents and burrs can be removed with a fine-grained sanding stone.
14. Check the pressure reducing valve spring for residual deformation and bending. Replace the damaged spring.
15. Check the gears for metal chipping, scoring and tooth wear. Replace damaged gears or gears with noticeable increased one-sided tooth wear.
16. Assemble the pump in the reverse order of disassembly.