Engine System Operation and Tests
CHECK FOR EXCESSIVE ENGINE
CRANKCASE PRESSURE (BLOW-BY)
Excessive blow-by coming out of the crankcase breather
tube (A) indicates that either the turbocharger (if
equipped) seals are faulty or the piston rings and cylinder
liners are not adequately sealing off the combustion
chamber. This is a comparative check that requires some
experience to determine when blow-by is excessive.
Run engine at high idle and check crankcase breather
tube. Look for significant fumes and/or dripping oil coming
out of the breather tube at fast idle, with no load.
If excessive blow-by is observed, perform the following to
determine if the turbocharger (if equipped) is causing the
1. Remove the turbocharger oil drain line where it
connects to the engine block and run line into a
2. Run engine at high idle, slightly loaded and determine
if boost pressure is forcing oil through the drain line,
and check crankcase breather tube to determine if
blow-by has decreased.
3. If it appears that boost pressure is forcing oil through
the drain line, and/or blow-by decreases with the drain
line disconnected from block, replace the turbocharger,