ENGINE DIAGNOSTIC TEST PROCEDURES
Figure 14. Checking Air Cleaner Restriction
400-Series On-Highway and OEM Only
(Turbocharged Application Shown)*
Remote Mounted Air Cleaner
Restriction Test Gauge (Magnehelic)
Figure 15. Top View of Dual Element Air Cleaner
Air Cleaner Restriction Connection
Secondary (Inner) Element
Air Cleaner Housing
Test the restriction of the secondary (inner) element as
Refer to Figure 16.
Remove and tap the air cleaner outlet pipe (1
approximately 3 inches below the air clean housing
(2). Always tap in a straight section o pipe+ and
clean tap thoroughly and reinstall Do not allow debris
to enter air intake system
+ Cover intake piping to prevent entrance of foreign
material into the engine.
Attach restriction test gauge (magnahelic) (3) to air
cleaner outlet pipe tap.
Test restriction with both the primary and secondary
elements installed in the housing. Maximum
allowable restriction is 6.2 kPa (2E in. H20) under full
load and rated speed for turbocharged engines.
If maximum restriction is exceeded, remove outer
element* and recheck restriction to determine useful
life of inner element.
*Primary (outer) element is serviceable. (Can be
cleaned). The primary element must be replaced after
six cleanings or annually whichever occurs first.
Secondary (inner) element is not serviceable and
must be replaced if maximum restriction is sensed.
NOTE: A low air cleaner restriction reading or a lack
of movement by the air cleaner restriction indicator
could be a plugged sintered fitting. There are two
different types of this fitting (Figure 17). The first
fitting has a filter screen in the fitting. This screen
can become plugged and not allow a correct air
cleaner restriction reading to be taken. If this type of
fitting is found, drill center of screen with a 1/32"
size drill. This fitting is welded in place and is not a
serviceable part. The other type of fitting has a 0.51
mm (0.020 in) orifice fitting. This type of fitting can
be easily cleaned with a fine piece of wire.
Reworking the first type fitting and cleaning the
second type fitting before running (diagnostic tests
will eliminate false air cleaner restriction readings.
Printed in United States of America