Clogged Atmospheric Pressure Sensors Caterpillar

OFF-HIGHWAY TRUCKS

OFF-HIGHWAY TRACTORS

WHEEL TRACTORS

WHEEL LOADERS

EXCAVATORS

Problem:

The atmospheric pressure sensors on the 3500 and 3500B electronic engines in these machines are vented to the atmosphere through a 3K-6905 or 9G5127 Breather Valve. These valves, which are located behind the engine Electronic Control Module (ECM) on the front of the engine (see the illustration), may become clogged with dirt, oil, and debris under normal operating conditions. A clogged breather valve may cause the engine to derate unexpectedly due to false high air filter restriction warnings or high altitude derates.

Solution:

To eliminate unexpected high air filter restrictions warnings or high altitude derates, the 3K-6905 or 9G5127 Breather Valves should cleaned or replaced periodically or when clogged. Valve may be cleaned with water or solvent. However, do NOT wash the valve with a pressure washer because of the valve's proximity to the ECM.

FRONT VIEW OF TYPICAL MACHINE ENGINE

Alternator (A).

1923 ECM (B).

Water Pump (C).

3K-6905 or 9G-5127 Breather Valve (1).

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