BASIC ENGINE ARRANGEMENT 4N3571 - Caterpillar

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Service indicator
Some engines may be equipped with a different service indicator.Observe the service indicator. Clean the air cleaner element or replace the element when the following conditions occur:
The yellow diaphragm enters the red zone.
The red piston locks in the visible position.
The air restriction reaches 3.7 kPa (15 inches of H2O).Inspect the service indicator daily for cracks, holes, or loose fittings. If any of these conditions are present, repair the service indicator or replace the service indicator.Test the Service Indicator
Service indicators are important instruments.
Check for ease of resetting. The service indicator should reset in less than three pushes.
Check the movement of the yellow core when the engine is accelerated to the engine rated rpm. The yellow core should latch approximately at the greatest vacuum that is attained.If the service indicator does not reset easily, or if the yellow core does not latch at the greatest vacuum, replace the service indicator. If the new service indicator will not reset, the fitting for the service indicator may be plugged.
Illustration 2 g00351792
Porous filter
A porous filter is part of a fitting that is used for mounting of the service indicator. Inspect the filter for cleanliness. Clean the filter, if necessary. Use compressed air or a clean, nonflammable solvent.The service indicator may need to be replaced frequently in environments that are severely dusty. Replace the service indicator annually regardless of the operating conditions. Replace the service indicator when the engine is overhauled, and whenever major engine components are replaced.Note: When a new service indicator is installed, excessive force may crack the top of the service indicator. Tighten the service indicator to a torque of 2 N m (18 lb in).