1. Remove the oil pump from the vehicle (see Removing and installing the oil pump).
2. Drain the oil from the pump.
3. Remove the front crankshaft oil seal from the housing bore using any pointed tool (e.g. a screwdriver).
4. Unscrew the pressure relief valve plug from the oil pump housing.
5. Remove the spring and plunger of the pressure reducing valve from the housing cavity.
WARNING: The pressure relief valve spring is pre-tensioned. Remove the plug very carefully to avoid injury.
6. Remove the screws securing the pump cover…
7….and remove the lid.
8. Remove the leading… from the housing cavity
9….and the driven gear of the pump.
10. Wash the pump body and removed parts, remove dirt and deposits. Remove dense varnish deposits from the internal cavities of the pump, having softened them with a solvent beforehand.
USEFUL TIP: Varnish oil deposits are easily removed with commercially available engine flushes (so-called "five-minute cleaners") or carburetor cleaners.
11. Inspect the pump body and cover.
If there are cracks, scratches, casting defects, damaged threaded holes, replace the housing (as it cannot be repaired) or the pump assembly.
12. Check the plunger of the pressure reducing valve for scratches and signs of sticking.
Small dents and burrs can be removed with a fine grit sanding block.
13. Check the pressure reducing valve spring for residual deformation and bending.
Replace a spring that is too compressed or damaged.
14. Check the gears for metal chipping, scoring and tooth wear. Replace damaged gears or those gears that show visually increased one-sided tooth wear.
15. Check the axial clearance between the ends of the gears and the surface of the pump cover.
This can be done in two ways.
16. In the first method, measure the thickness of the leading…
17….and the driven gear…
18….and also the depth of the bore in the housing for the gears. Calculate the axial clearance as the difference between the arithmetic mean of the bore depth and the thickness of the gears.
19. For the second method of checking, install the driven gear in the housing, place a metal ruler (or caliper) with the end on the housing and measure the gap between the housing and the ruler with a feeler gauge.
20. Measure the axial clearance of the drive gear in the same way.
21. The maximum allowable clearances measured by both methods should be 0.045–0.100 mm for the driven gear and 0.035–0.085 mm for the driving gear. If at least one of the clearances does not correspond to the specified value, replace the housing or the pump assembly.
22. Assemble the pump in the reverse order of disassembly. Before pressing into the pump cover, lubricate the front crankshaft oil seal with engine oil. Apply anaerobic thread lock to the threads of the pressure relief valve plug and tighten the plug.