Disassembly
Remove plug 1, spring 2 and plunger 3 of the pressure reducing valve.
Remove cover 4 of the oil pump.
Rinse and blow out the oil pump parts with compressed air.
Checking the technical condition of parts
Measure the free length of the pressure reducing valve spring, which should be 68 mm.
Check the clearances between the outer rotor and the oil pump housing and between the inner and outer rotors, as well as the alignment of the outer rotor relative to the end face of the oil pump housing.
If the clearance between the outer rotor and the pump housing is excessive, replace the pump housing. If the clearance between the inner and outer rotors exceeds the limit, replace the rotors. If the outer rotor sink exceeds the limit, replace the oil pump housing.
To remove the inner rotor, press the oil pump drive flange using a universal two-lever puller. It is forbidden to press out the flange with a lever.
When pressing on the oil pump drive flange, it is necessary to maintain the dimension «A» (see photo), equal to 32.7±0.1 mm (models «518», «520») or 44.3±0.1 mm (models «525», «528»).
On models «525» And «528» there is a vent hole in the oil pump housing connecting the discharge cavity with the pressure reducing valve (it is forbidden to drill such a hole on pumps in the design of which it is not provided). Clean this hole with copper wire and blow with compressed air.