The tightening torque for spark plugs varies depending on the thread diameter of the plug. If a plug is tightened with a torque exceeding the recommended torque, the thread could break. See Photo 1.
- 1) Apart from overtightening, another possible cause of a thread break in a plug is the application of an anti-seizure agent or oil when fitting the plug, since this lowers the friction resistance and means that the thread can be turned more than necessary.
Never use an anti-seizure agent or oil.
- When fitting a spark plug, use a torque wrench and tighten it with the recommended torque.
For situations where it is not possible to use the list of recommended torques and a torque wrench, the turning angles to achieve correct tightening are also given below.
| Plug thread diameter |
Tightening torque |
|---|
| 18mm |
35 – 40N · m(3.5 – 4.0kgm) |
| 14mm |
25 – 30N · m(2.5 – 3.0kgm) |
| 12mm |
15 – 20N · m(1.5 – 2.0kgm) |
| 10mm |
10 – 12N · m(1.0 – 1.2kgm) |
| 8mm |
8 – 10N · m(0.8 – 1.0kgm) |
| Tightening torque |
|---|
| Taper seat type (plug with no gasket) |
10 – 20N · m(1.0 – 2.0kgf-m) |
| Plug thread diameter |
New plugs |
Reused |
|---|
| 18,14mm( * is excluded. ) |
About 1/2 – 2/3 rotations(180° – 240°) |
About 1/12 rotations(30°) |
| * BCPR6ED BCPR7EKD |
About 1/3 rotations(120°) |
About 1/12 rotations(30°) |
| BKR5EKUC BKR6EKUC |
| BKR6EKE HB6AIX-11P |
| IZFR5C R6469-9 |
| BCPR6EKD BCPR7EDIX |
| BKR5EKUD BKR6EKUD |
| BKR5ETUA HB6BIX-11P |
| PZFR5C R6918C-9 |
| 12mm( * is excluded. ) |
About 1/2 rotations(180°) |
About 1/12 rotations(30°) |
| * DILZKR7A11GSILZKR7B-11SR2556B-*ILZKR7B11GSSILKR8A-SR2558A-* |
About 1/4 rotations(90°) |
About 1/8 rotations(45°) |
| 10mm( * is excluded. ) |
About 1/2 rotations(180°) |
About 1/12 rotations(30°) |
| *CPR6EA-9SCR9EH-9SIMR9C-9HESIMR9E-9HESSILMAR10A9SSILR7A7SR0409B *CR8EH-9SIMR8C-9HESIMR9D-9HSILMAR9A9SSILR6A7SSPMR8A6HDGR0451B-8 |
About 1/6 rotations(60°) |
About 1/12 rotations(30°) |
| 8mm |
About 1/3 rotations(120°) |
About 1/12 rotations(30°) |
| Taper seat type (plug with no gasket) |
About 1/16 rotations(22.5°) |
About 1/16 rotations(22.5°) |
| Copper gasket type |
About 1/12 rotations(30°) |
About 1/24 rotations(15°) |
The heat value enters for * of the end of R2556B-*, R2558A-*, and R0409B-*.
