Kohler LH630-775 Service Manual page 24

• Check the condition of the oil. Drain the oil into a
container - the oil should flow freely. Check the
appearance (color) of the oil, and for metal chips
or foreign particles. A milky, opaque color denotes
the presence of engine coolant in the crankcase oil.
Sludge is a natural by-product of combustion;
a small accumulation is normal. Excessive
sludge formation could indicate overrich
carburetion, weak ignition, overextended oil
change intervals or wrong weight or type of oil
was used, to name a few.
NOTE: It is good practice to drain oil at a
location away from the workbench. Be
sure to allow ample time for complete
drainage.
Cleaning The Engine
After inspecting the external condition of the engine,
clean the engine thoroughly before disassembling it.
Also clean individual components as the engine is
disassembled. Only clean parts can be accurately
inspected and gauged for wear or damage. There are
many commercially available cleaners that will quickly
remove grease, oil, and grime from engine parts. When
such a cleaner is used, follow the manufacturer's
instructions and safety precautions carefully.
Make sure all traces of the cleaner are removed before
the engine is reassembled and placed into operation.
Even small amounts of these cleaners can quickly break
down the lubricating properties of engine oil.
Possible Cause
1. Crankcase breather clogged or inoperative.
2. Seals and/or gaskets leaking. Loose or
improperly torqued fasteners.
3. Piston blowby or leaky valves. (Confirm by
inspecting components.)
4. Restricted exhaust.
No Crankcase Vacuum/Pressure in Crankcase
Basic Engine Tests
Crankcase Vacuum Test
A partial vacuum should be present in the crankcase
when the engine is operating. Pressure in the
crankcase (normally caused by a clogged or
improperly assembled breather) can cause oil to be
forced out at oil seals, gaskets, or other available spots.
Crankcase vacuum is best measured with either a
water manometer or a vacuum gauge (see Section 2).
Complete instructions are provided in the kits.
Test the crankcase vacuum with the manometer as
follows:
1. Insert the stopper/hose into the oil fill hole. Leave
the other tube of manometer open to atmosphere.
Make sure the shut-off clamp is closed.
2. Start the engine and run at no-load full throttle
speed (3200 to 3750 RPM).
3. Open the clamp and note the water level in the
tube.
The level in the engine side should be a minimum
of 10.2 cm (4 in.) above the level in the open side.
If the level in the engine side is less than specified
(low/no vacuum), or the level in the engine side is
lower than the level in the open side (pressure),
check for the conditions in the table below.
4. Close the shut-off clamp before stopping the
engine.
Solution
1. Replace breather assembly (valve cover).
2. Replace all worn or damaged seals and gaskets.
Make sure all fasteners are tightened securely.
Use appropriate torque values and sequences
when necessary.
3. Recondition piston, rings, cylinder bore, valves,
and valve guides.
4. Repair/replace restricted muffler/exhaust system.
Section 3
Troubleshooting
3.3
3