Impreza RS Coupe AWD F4-2.5L SOHC (1999)
1. Measure inside diameter of valve rocker arm and outside diameter of valve rocker shaft, and determine the difference between the two (= oil
clearance).
Clearance between arm and shaft:
Standard: 0.020 - 0.054 mm (0.0008 - 0.0021 inch)
Limit: 0.10 mm (0.0039 inch)
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If oil clearance exceeds specifications, replace valve rocker arm or shaft.
NOTE: Replace valve rocker arm or shaft, whichever shows greater amount of wear.
Rocker arm inside diameter: 22.020 - 22.041 mm (0.8669 - 0.8678 inch)
Rocker shaft diameter: 21.987 - 22.000 mm (0.8656 - 0.8661 inch)
2. Measure inside diameter of rocker shaft support and outside diameter of valve rocker shaft, and determine the difference between the two (=
oil clearance).
Clearance between support and shaft:
Standard: 0.005 - 0.039 mm (0.0002 - 0.0015 inch)
Limit: 0.05 mm (0.0020 inch)
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If oil clearance exceeds specifications, replace rocker shaft support or shaft.
NOTE: Replace rocker shaft support or shaft, whichever shows greater amount of wear.
Rocker shaft support inside diameter: 22.005 - 22.026 mm (0.8663 - 0.8672 inch)
Rocker shaft diameter: 21.987 - 22.000 mm (0.8656 - 0.8661 inch)
3. If cam or valve contact surface of valve rocker arm is worn or dented excessively, replace valve rocker arm.
4. Check that valve rocker arm roller rotates smoothly. If not, replace valve rocker arm.
2. INTAKE AND EXHAUST VALVE ROCKER SHAFT
Visually check oil relief valve of shaft end for any of the following abnormalities.
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Breaks in check ball body
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Foreign particles caught in valve spring
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Oil leakage at check ball
CAUTION: Repair or replace valve rocker shaft as necessary.