Kohler LH630-775 Service Manual page 89

Section 7
Cooling System
5. Observe the system pressure on the gauge.
Gauge Needle Holds Steady
If the gauge needle holds steady, there should be no
serious leaks in the system. It is however,
recommended that all connections be checked for
overall condition anyway, using a flashlight.
Gauge Needle Drops Slowly
If the gauge needle drops slowly it indicates the
presence of a small leak or seepage. Check all
components and connections for signs of leakage.
Check the condition of the radiator hoses. If they swell
excessively while testing the system, they may be
weak and should be replaced.
Gauge Needle Drops Quickly
A steady drop or loss of pressure indicates serious
leakage is occurring within the system, which must
be located and corrected before the engine is returned
to service.
7.8
If a pressure loss is noted:
1. With pressure on the system, apply a soap/water
solution and check all joint connections, hoses,
and cooling system components for external
leakage. Repair or replace as required.
2. Remove the dipstick and check the appearance of
the oil in the crankcase. Another method would
be to remove an oil drain plug and drain a small
amount of oil for inspection. A milky or an
opaque color, similar to chocolate milk, indicates
the presence of engine coolant in the oil. Check for
a blown head gasket (step 3 below) or a possible
crack or internal leakage from the water jacket.
3. Remove the spark plugs. Apply 14-15 lbs. of
pressure and listen/inspect for internal coolant
leakage into the cylinder/combustion chambers.
This can denote a head gasket failure/leak. If
required, further test by performing a ''Cylinder
Leakdown Test'' as described in Section 3.