Checking the side clearance of the new piston rings
Prerequisite
Piston cleaned.
- Note the arrangement of the piston rings:
Upper piston ring (1): Plain rectangular compression ring (engraving must point upwards)
Center piston ring (2): Taper faced piston ring (engraving must point upwards)
Oil scraper ring (3): consisting of 2 piston rings (O1) and (O3) with spring (O2) in the center
Check
- Use a feeler gauge to check the side clearance of the new upper piston ring (plain rectangular compression ring) .
- Determining the correct set of the piston ring (1) (see applicable BMW parts catalogue):
| Engine | Set of piston rings | Pistons | Side clearance of the upper piston ring |
|---|---|---|---|
| B38M1 ECE | 8 693 017 | 8 678 931 | 0.02 - 0.07 mm |
| B38M1 ECE | 8 693 017 | 9 494 399 | 0.04 - 0.08 mm |
| B48M1 ECE | 8 693 017 | 8 678 931 | 0.02 - 0.07 mm |
| B48M1 ECE | 8 693 017 | 9 494 399 | 0.04 - 0.08 mm |
| B38M1 CN | 8 693 017 | 8 678 931 | 0.02 - 0.07 mm |
| B38M1 CN | 9 847 276 | 8 681 079 | 0.035 - 0.085 mm |
| B48M1 CN | 8 693 017 | 8 678 931 | 0.02 - 0.07 mm |
| B48M1 CN | 9 847 276 | 8 681 079 | 0.035 - 0.085 mm |
| B48O1 ECE+CN | 8 693 017 | 8 678 934 | 0.02 - 0.07 mm |
| B48T1 ECE+CN | 9 846 014 | 9 488 343 | 0.03 - 0.07 mm |
| B58M1 | 9 847 276 | 8 681 079 | 0.035 - 0.85 mm |
| B58O1 | 9 693 017 | 8 678 934 | 0.02- 0.07 mm |
Result
» The side clearance is outside the tolerance.
Measure
- Replace the piston.
- Note the arrangement of the piston rings:
Upper piston ring (1): Plain rectangular compression ring (engraving must point upwards)
Center piston ring (2): Taper faced piston ring (engraving must point upwards)
Oil scraper ring (3): consisting of 2 piston rings (O1) and (O3) with spring (O2) in the center.
Check
- Use a feeler gauge to check the side clearance of the new middle piston ring (taper faced piston ring) .
- Determining the correct set of the piston ring (1) (see applicable BMW parts catalogue):
| Engine | Set of piston rings | Pistons | Side clearance of the piston ring in the center |
|---|---|---|---|
| B38M1 ECE | 8 693 017 | 8 678 931 | 0.03 - 0.07 mm |
| B38M1 ECE | 8 693 017 | 9 494 399 | 0.03 - 0.07 mm |
| B48M1 ECE | 8 693 017 | 8 678 931 | 0.03 - 0.07 mm |
| B48M1 ECE | 8 693 017 | 9 494 399 | 0.03 - 0.07 mm |
| B38M1 CN | 8 693 017 | 8 678 931 | 0.03 - 0.07 mm |
| B38M1 CN | 9 847 276 | 8 681 079 | 0.015 - 0.06 mm |
| B48M1 CN | 8 693 017 | 8 678 931 | 0.03 - 0.07 mm |
| B48M1 CN | 9 847 276 | 8 681 079 | 0.015 - 0.06 mm |
| B48O1 ECE+CN | 8 693 017 | 8 678 934 | 0.03 - 0.07 mm |
| B48T1 ECE+CN | 9 846 014 | 9 488 343 | 0.025 - 0.07 mm |
| B58M1 | 9 847 276 | 8 681 079 | 0.015 - 0.06 mm |
| B58O1 | 9 693 017 | 8 678 934 | 0.03 - 0.07 mm |
Result
» The side clearance is outside the tolerance.
Measure
- Replace the piston.