MTU Detroit Diesel 183 Series Technical Publication page 149

Task Description
If pressure is too low:
Vent opening to diaphragm obstructed
Diaphragm does not close because spring force is too
high.
Spring is not properly secured or diaphragm is torn
If pressure is too high:
Leaks at connection points of the oil separator to the
intake pipe.
Intake depression is insufficient due to leakage in intake
ducts.
Filter section of oil separator contaminated.
20080/1 E 98-12
There is a vacuum in the cylinder crankcase if the
water column at the connected end of the tube (right) is
higher than at the free end (left) - (maximum - 100 mm
water column).
The correct level is indicated as the difference between
the two water surfaces.
Note
The pressure in the crankcase over the entire engine
speed range must lie between
+10 mm water column (overpressure) and -100 mm
water column (vacuum).
If the limit values are exceeded, this could have the
following causes:
Remedy:
Clear vent opening.
Replace vent hose.
Replace oil separator.
Remedy:
Check that connection points are correctly seated.
Check air filter and intake ducts to the exhaust
turbocharger (danger of damage due to dust).
Clean oil separator, replace if necessary.
Group 01
Subgroup 9751
Page 3