C4.4 and C6.6 Industrial Engines and Engines for Caterpillar Built Machines Caterpillar

Probable Causes

• High ambient air temperature

• Intake air restriction and/or high altitude

• Intake air from a heated area

• Intake manifold air temperature sensor and/or circuit

• Insufficient ambient air flow over the engine

• Reduced ambient air flow through the air charge cooler

• Reduced flow of intake air through the air charge cooler

Recommended Actions

High Ambient Air Temperature

1. Determine if the ambient air temperature is within the design specifications for the cooling system and the air charge cooler.

2. When the ambient temperature exceeds the capability of the cooling system or the air charge cooler, operate the engine at a reduced load or operate the engine at a reduced speed.

3. When possible, modify the cooling system and the air charge cooler in order to make the system suitable for local conditions.

Intake Air Restriction and/or High Altitude

Low air pressure at the air intake for the turbocharger can be caused by a restriction in the air intake or a high altitude. When the pressure of the intake air is low, the turbocharger (if equipped) works harder in order to achieve the desired intake manifold pressure. This increases intake air temperature.

Measure the intake manifold pressure while the engine is operating under load. For specific data, refer to the Technical Marketing Information (TMI) for the engine.

Intake Air Restriction

1. Check for blocked air filters. Check for obstructions in the air intake.

2. Replace the air filters or remove the obstruction from the air intake.

High Altitude

Make sure that the settings for the engine are correct for the altitude.

Intake Air from a Heated Area

1. Ensure that the air inlet system is not receiving air from a heated area.

2. If necessary, relocate the air supply to the intake manifold to the outside of the engine enclosure.

3. Check for air leaks in the pipe between the air inlet and the inlet to the turbocharger compressor.

Intake Manifold Air Temperature Sensor and/or the Circuit

1. Allow the intake manifold air temperature sensor to cool and remove the sensor. Check the reading for the intake air temperature. If the sensor is operating correctly, the reading and the ambient temperature are approximately equal.

2. If the readings are approximately equal, reinstall the sensor.

3. If the reading is not correct, replace the sensor with a sensor that is known to be good. Verify that the fault is eliminated.

Insufficient Ambient Air Flow over the Engine

1. If equipped, check the condition of the cooling fan and the drive belt.

2. If equipped, check that the cooling fan is operating correctly.

Reduced Ambient Air Flow through the Air Charge Cooler

1. Check that the ambient air flow through the air charge cooler is not obstructed.

2. Inspect the air charge cooler for contamination and/or bent fins or damaged fins.

3. If necessary, clean the air charge cooler.

4. If necessary, carefully straighten any bent fins on the air charge cooler.

Reduced Flow of Intake Air through the Air Charge Cooler

1. Check for contamination in the air pipe that connects the turbocharger to the air charge cooler.

   1. If dirt is found in the air pipe from the turbocharger to the air charge cooler, check all of the air inlet pipes upstream of the turbocharger for leaks.

   2. Clean all contaminated air inlet pipes or replace all contaminated air inlet pipes.

   3. Service the air cleaner and replace the air cleaner element.

2. If a thick oil film is found in the air pipe, inspect the turbocharger compressor housing. Examine both the inlet to the turbocharger compressor housing and the outlet from the turbocharger compressor for oil.

   1. If oil is found in the inlet to the turbocharger compressor housing, the oil originates from the engine crankcase breather.

   2. If oil is found in the outlet from the turbocharger compressor housing but oil is not found in the inlet to the compressor housing, the oil originates from the seals for the turbocharger bearings.