Lubricating Oil System Diagnostics (007-048)
B3.9 and B5.9 Series Engines
Section 7 - Lubricating Oil System - Group 07
Using a filter for a six-cylinder engine on a four-cylinder
engine does not allow extended change interval. Never
use a filter for a four-cylinder engine on a six-cylinder
engine because of the reduced material holding capa-
bility and increased chance of plugging. Failure to do
so can cause engine damage.
Lubricating Oil Filter
After the oil is cooled, it flows through the full-flow oil filter.
The filter for the six-cylinder engine is longer than the filter
for the four-cylinder engine.
A plugged filter will cause a gradual loss of oil pressure by
approximately 69 kPa [10 psi]. The pressure will return to
normal when the filter bypass valve opens. If not corrected,
this will result in severe engine wear, as the engine is
running on unfiltered oil when the bypass valve is open.
Lubricating Oil Gauge
Check the lubricating oil gauge and sending unit to make
sure they are operating correctly by verifying the pressure
with a manual gauge connected to the main oil rifle.
Lubricating Oil Suction Tube
A loose suction tube, damaged gasket, or crack in the
suction tube can cause a temporary loss of prime for the
oil pump. The engine will have low pressure or no oil
pressure at starting, followed by normal oil pressure.