Kohler KDI 1903M Workshop Manual page 46

2
3 against the valve stem, thus eliminating any system
play. Thanks to the spring extension, the tappet extends",
creating a small depression in the chamber B, making the
non-return valve 4 open, and allowing the oil in the
chamber A to pass to chamber B, restoring the proper
amount of oil required to eliminate any play in the valves.
2.16.5.2 Difficult operating conditions
For proper operation on the hydraulic tappets it is essentia that the low pressure chamber of the piston
3 is always full of oil.
In some conditions this may not occur (due to the fact that the oil leaks away when the engine is
switched off, which can also partially drain the tappets). This situation will be the cause of clearances
that will result in a characteristic noise similar toa ticking sound.
1. When the engine is cold, the tappet filling time could be very long if the oil used is not suitable
for the specific environmental conditions
2. If the engine is very hot: at idle speed, oil pressure may be low, and small air bubbles could form
in the circuit. Because of this, this compressing the tappet slightly and producing valve play
which is responsible for the ticking sound. On account of this, the tappet compresses slightly
giving rise to a valve clearance, thus generating a slight ticking sound, which however
disappears rapidly (MAX 10 seconds) once normal operating conditions have been restored.
Anyway the duration of ticking Anyway the duration of ticking sound must be MAX 30 seconds. If not,
the problem is surely due to the poor quality of the oil, wear or impurities that, transported by the oil, can
infiltrate between the ball valve and its seat inside the piston, compromising the operation of the tappet
itself; In these cases, the only solution is to replace the oil or hydraulic tappets.
The prolonged persistence of the ticking sound or abnormal noise must be investigating in order to
prevent any malfunctions; if necessary, replace the hydraulic tappets and engine oil.
EN 46
TECHNICAL INFORMATION
(Tab. 2.2)