Withdrawal
1. Remove the oil filter (see chapter 1, section 12).
2. Remove the oil filter flange mounting bolts, remove the pressure regulator valve and spring (see section 14).
3. Remove the camshaft chain cover (see section 13).
4. Turn away bolts of fastening of a cover of the oil pump and a cover of the gas-distributing mechanism (see illustration).
15.4. The oil pump cover is attached to the inside of the timing cover. To loosen the screws, a Torx T-30 wrench is required
5. Remove the oil pump cover and gear assembly (see illustration). Pay attention to how the gears are installed; they must be installed in the same way.
15.5. Oil pump disassembled: 1 - screw, 2 - cap, 3 - outer gear, 4 - inner gear, 5 - camshaft chain cover
Examination
6. Clean all parts with solvent and dry with compressed air (if there is appropriate equipment).
Attention! Don't forget eye protection.
7. Check all parts for wear and scratches. Replace worn and damaged parts.
8. Check the bypass valve (see section 14).
9. Replace the gears in the timing cover.
10. Measure the gap between the outer gear and the housing with a feeler gauge (see illustration).
15.10. Measuring the clearance between the outer gear and the housing using a thickness gauge
11. Measure the gap between the outer and inner gears with a feeler gauge in several places (see illustration).
15.11. Measuring the gap between the inner and outer gears using a thickness gauge
12. Using an indicator or a feeler gauge, measure the end clearance of the gear (distance from gear to cover gasket surface) (see illustration).
15.12. Measuring the end clearance of gears using a special clamp and a dial gauge
13. Check for deformation of the pump cover by placing a precision straight edge across the cover and trying to insert a feeler gauge between the cover and the ruler.
14. Compare the measurements with the technical data in this chapter. Replace any worn or damaged parts with new ones.
Installation
15. Remove all gears and fill pump cavity with grease.
16. Insert gears. Check that the grease is squeezed out into each cavity. Failure to do so may result in damage to the pump due to lack of oil pressure on initial start-up.
17. Install the pump cover using only a new GM gasket; the thickness of this spacer is essential to maintain the correct clearance.
18. Install pressure regulator valve and spring.
19. Install the timing cover.
20. Install oil filter and check oil level (see chapter 1, section 12). Start the engine, let it run and check for correct oil pressure, then carefully inspect for oil leaks at the timing cover.