Air Intake Restriction Gauge
The air intake restriction gauge indicates the vacuum on the engine side of the air cleaner. On standard installations, it is mounted on the air cleaner. As an option for easier viewing, an air intake restriction indicator (see Fig.) can be mounted on the auxiliary dash panel.
Fig. 1, Air Intake Restriction Indicator
Note: Rain or snow can wet the filter element and cause a temporary high reading.
Air intake restriction vacuum is measured in inches of water (inH2O). For vehicles equipped with a graduated indicator or a restriction gauge on the dash, check the gauge with the engine off. If the yellow signal stays locked in the red zone once the engine is shut down, or is at or above the values shown in Table., the air cleaner element needs to be replaced.
Table 1, Air Intake Maximum Restriction Values
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Air Intake Maximum Restriction Values: (inH2O) |
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|
Engine Make |
Pre-EPA07 Engines |
EPA07 Engines |
|
Caterpillar |
25 |
— |
|
Cummins |
25 |
25 |
|
Detroit™ |
20 |
22 |
|
Mercedes-Benz |
22 |
22 |
Table 1, Air Intake Maximum Restriction Values
Vehicles may be equipped with a go/no-go restriction indicator without graduations (see Fig.) instead of a graduated indicator.
Fig. 2, Manual-Reset Air Restriction Indicator, Go/No-Go
If air restriction exceeds the maximum allowable value, operate the vehicle for one more day, making sure not to run the engine over rated rpm. Refer to the engine operation manual for more information on rated rpm for your engine.
If air restriction exceeds the maximum value again, replace the air cleaner element. For instructions, refer to Group 09 of the Century Class Trucks Workshop Manual.