Yanmar 3TNV Series, Service Manual

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2. Inspection and Adjustment
(2) V-belt tension check
When there is not enough tension in the V-belt, the
V-belt will slip making it impossible for the alternator to
generate power and cooling water pump and cooling
an will not work causing the engine to overheat. f
Check and adjust the V-belt tension (deflection) in the
following manner.
[NOTICE]
Be especially careful not to splash engine oil on the
V-belt, because it will cause slipping, stretching and
aging of the belt.
1) Press the V-belt with your thumb [approx.
98N(10kgf)] at the middle of the V-belt span to
check the tension (deflection).
Available positions to check and adjust the V-belt
tension (deflection) are at the A, B or C direction
as shown in the illustration right.
You may choose a position whichever you can
easily carry out the check and adjustment on the
machine unit.
"New V-belt" refers to a V-belt, which has been
used less than 5 minutes on a running engine.
"Used V-belt" refers to a V-belt, which has been
used on a running engine for 5 minutes or more.
The specified deflection to be measured at each
position should be as follows.
(Unit: mm)
Direction A B C
For used V-belt 10 14 7 10 9 13
For new V-belt 8 12 5 8 7 11
2) If necessary, adjust the V-belt tension (deflection).
To adjust the V-belt tension, loosen the set bolt
and move the alternator to tighten the V-belt.
After replacing with a new V-belt and adjusting it,
run the engine for 5 minutes and readjust the
deflection to the value in the table above.
3) After replacing with a new V-belt and adjusting it,
run the engine for 5 minutes and readjust the
deflection to the value in the table above.
4) Visually check the V-belt for cracks, oiliness or
wear. If any, replace the V-belt with new one.
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