Volvo D11F - Manual (Page 67)

Maintenance and Service 63
ENGINE AIR FILTER
Continued operation with the gauge showing in the red may cause damage to
the engine. Operating the engine with a damaged filter allows dust to pass
directly into the engine, causing damage. Replace damaged or clogged filters.
The engine air filter is monitored by a pressure restriction gauge mounted on
the air filter housing. The gauge may be connected to the instrumentation to
give a telltale signal when the air filter needs to be changed; see the vehicle
Operator's Manual. A manual gauge needs to be inspected regularly. Replace
the filter according to the gauge or after a maximum of two years, whichever
comes first. Optional extra filter insert should be changed with every third
main air filter.
Pressure Restriction Gauge
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