Service Manual

ISB, ISBe and QSB (Common Rail [...] Crankcase Blowby, Measure
Section 14 - Engine Testing - Group 14 Page 14-27
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Crankcase Blowby, Measure (014-010)
General Information
Excessive crankcase blowby can indicate an engine or
engine-related component malfunction that allows
combustion gases or air to enter the crankcase. This
results in the buildup of higher than normal crankcase
pressure, which results in increased levels of blowby.
This procedure describes how to measure crankcase
blowby and how to determine what component is
malfunctioning.
Blowby is typically measured for the following situations:
• Verifying engine break-in after an engine rebuild
• Troubleshooting for excessive lubricating oil out of the
crankcase breather tube, commonly referred to as oil
carryover (for open crankcase ventilation systems)
• Troubleshooting oil in the air intake system (for closed
crankcase ventilation systems)
• Troubleshooting high crankcase pressure (for engines
equipped with a crankcase pressure sensor)
• Troubleshooting possible internal engine damage
(worn piston rings, valve stem seals, or guides,
turbocharger, air compressor, etc.).
NOTE: For specific crankcase gases (blowby) symptom
information and direction, reference the Crankcase Gases
(Blowby) Excessive troubleshooting symptom tree in
Section TS of the appropriate engine service manual.
The following measure step will give general guidelines
for measuring blowby relative to the above situations.
NOTE: Some illustrations in this procedure do not show
actual engine configurations. However, the procedure is
the same.