Engine Maintenance
119
Crankcase Breather
Gases formed in the crankcase are directed to the
intake manifold. Harmful vapors that would
otherwise collect in the crankcase and
contaminate the oil, or escape to the outside, are
drawn back into the engine and burned.
The crankcase breather is located in the valve
cover. A restrictor is cast into the fitting for the
breather hose on the intake manifold. The
restrictor limits the flow of gases from the
crankcase to the intake manifold and keeps the
crankcase pressure from getting too low in
vacuum. A breather hose connects the crankcase
breather to the intake manifold.
Normal crankcase pressures with a new air
cleaner are 0 to 12 in. (0 to 300 mm) H
2
O of
vacuum. The vacuum will increase as the air
cleaner gets dirty and becomes more restrictive.
Check the air restriction indicator before checking
the crankcase pressure. Replace the air cleaner if
the reading on the air restriction indicator exceeds
20 in. (508 mm) H
2
O of vacuum. A dirty air
cleaner may cause excessive vacuum, leading to
oil carry over and high oil consumption.
The crankcase breather and the breather hose
should be inspected when the air cleaner element
is replaced to make sure they are not plugged or
damaged. Inspect the insulation to make sure it is
in place and undamaged. The insulation is used to
prevent freezing in cold weather.
The following items can effect the crankcase
pressure readings.
EMI 3000 Air Cleaner
The EMI 3000 air cleaner is a dry element air
cleaner. Replace the EMI 3000 air cleaner element
at 3,000 hours or 2 years, whichever occurs first.
Figure 199: EMI 3000 Air Cleaner Assembly
Figure 200: EMI 3000 Air Filter Element
1.
Breather Hose
5.
Baffle Breather
2.
Insulation
6.
Baffle Plate
3.
Breather Cover
7.
Intake Manifold
4.
O-Ring
8.
Restrictor Location
Figure 198: Crankcase Breather
3
4
5
6
7
2
1
8
Crankcase
Pressure
Effect
Typical Cause
Increase
Piston Rings Stuck or Worn
Increase
Breather Hose or Restrictor
Plugged with Dirt or Ice
Decrease
Air Cleaner Dirty or Plugged
ARA1914
ARA1915
