Volvo Penta D4 Operator's Manual page 54

Maintenance: Engine general
52
Changing the air filter
Remove the air filter cover. Remove the old air filter.
Clean the air filter cover/housing if necessary. Take
care not to allow impurities to enter the engine. Fit the
new air filter and the air filter cover.
Changing the crankcase ventilation filter
Unscrew the lid and remove the old filter. Clean the fil-
ter cover/housing if necessary. Take care not to allow
impurities to enter the engine. Fit the new filter.