Kohler CV11-16 Service Manual page 23

Basic Engine Tests
Crankcase Vacuum Test
A partial vacuum should be present in the crankcase
when the engine is operating at normal temperatures.
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 a water
manometer or vacuum/pressure test gauge. See
Section 2. Complete instructions are provided with the
testers.
Test the crankcase vacuum with the manometer as
follows:
1. Insert the rubber stopper into the oil fill hole. Be
sure the pinch clamp is installed on the hose and
use the tapered adapters to connect the hose
between the stopper and one of the manometer
tubes. Leave the other tube open to the
atmosphere. Check that the water level in the
manometer is at the "0" line. Make sure the pinch
clamp is closed.
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 with
cylinder leakdown test.
4. Restricted exhaust.
2. Start the engine and run at no-load, high idle
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 the same as the
open side (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.
To perform the test with the vacuum/pressure
gauge, insert the stopper as in step 1. Insert the
barbed gauge fitting into the hole in the stopper.
Be sure the gauge needle is at "0". Run the
engine, as in step 2, and observe the gauge
reading. Needle movement to the left of "0" is a
vacuum, and movement to the right indicates a
pressure.
Incorrect Vacuum in Crankcase
1. Disassemble breather, clean parts thoroughly,
reassemble, and recheck pressure.
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
Solution
3
3.3