FAW Jiefang Automotive 485, Руководство по эксплуатации и техническому обслуживанию

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Inspect the open gap, before the piston ring is fitted. Lie the piston ring flat to the place, which is
15
～
20mm away from the top face of cylinder; The open gap should, measured with a feeler gage,
be 0.25
～
0.4 mm. See Fig.6. Trimming with a file is possible if the gap is too small, and match it
again if the gap is too big. Additionally, it is necessary to use the feeler gage to measure the
end-face gap between piston ring and piston ring groove. The end-face gap for first gas ring
should be 0.05
～
0.082 mm; for second gas ring should be 0.03
～
0.062 mm; and for oil ring
should be 0.03
～
0.062 mm. See Fig.7.
1-Feeler gage 2-Piston ring 3-Cylinder liner
Fig. 6 Measuring the end-face gap of piston ring
Fig. 7 Measuring the end-face gap of piston ring
The piston rings should be removed and fitted back, by special tools. When fitting the rings,
opening of each ring should be staggered each other for 120
°
, and should not be at the direction
of piston pin.
During maintenance/repair, if the piston ring is found seized/dead and cannot move, it is
possible to immerse the ring in diesel oil (kerosene or gasoline) for 24h or longer, then tap gently
the ring to make it to be loosened. After that the ring should be taken out and then cleaned with
diesel oil or carbon tetrachloride.
Check each position of the piston for crack and scar. If defect(s) is found, renew it, and
replace the piston ring.
3. Piston pin
Before removing or fitting back the pin, fit a retaining ring at one end (or remove retaining
rings at two ends). Place the piston in engine oil (or boiled water), where the piston is heated to
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