SUPPORT AS 4211974 - Caterpillar

Measuring the Air Temperature and Air Pressure Across the Aftercooler
Remove all air leaks from the system to prevent engine damage. In some operating conditions, the engine can pull a manifold vacuum for short periods of time. A leak in the aftercooler or air lines can let dirt and other foreign material into the engine and cause rapid wear and/or damage to engine parts.
Illustration 1 g02646399
Test locations for the aftercooler temperature and pressure measurements (left side engine view)
(1) Port for measurements at outlet of the turbocharger compressor
(2) Ports for measurements at the inlet of the intake manifold (aftercooler air outlet) Perform measurements for pressure and temperature at the locations that are shown Illustration 1. Perform the measurements while the engine is under a normal mode operation. Record the test results in the following Table:
Table 2
Aftercooler Temperature and Pressure Measurements
Parameter 100% Load 75% Load 50% Load
"Compressor Out Pressure" (Inches Hg (ABS))
"Inlet Manifold Pressure" (Inches Hg (ABS))
"Compressor Out Temperature" (°F)
"Aftercooler Air Outlet Temperature" (°F) Compare the results of the test to values that are given in Technical Marketing Information (TMI). Look for similar results. If a large change in the temperature or the pressure differential is noticed, there may be a problem in the aftercooler circuit.If a large change for the pressure differential is discovered, check the air inlet system and the aftercooler circuit for restriction. Perform any necessary repairs. Refer to the topic "Inlet Manifold Pressure" for details that are related to troubleshooting the inlet air system.If a large change for the temperature differential is discovered, check the SCAC cooling system for a problem. Ensure that the aftercooler core is not restricted. If a restriction in the aftercooler core is suspected, refer to the topic "Measuring the Coolant Pressure Across the Aftercooler Core" for details.If a leak in the aftercooler core is suspected, refer to the topic "Aftercooler Core Leakage" for details.Measuring the Coolant Pressure Across the Aftercooler Core
Illustration 2 g02646019
Ports for measurement of the aftercooler coolant pressure (right side engine view)
(3) Outlet port for the aftercooler coolant
(4) Inlet port for the aftercooler coolant Perform measurements for the coolant pressure across the aftercooler core at the locations that are shown Illustration 1. Perform the measurements while the engine is under a normal mode operation.Compare your results to the following specifications that are for a new aftercooler core:These specifications were obtained under the following test conditions:Water flow in the SCAC system ... 79.5 L/min (21 US gpm)Specification for the water temperature at the inlet of the aftercooler core ... 54° to 75°C (129° to 134°F)Note: Ensure that consideration is given for the test conditions during the test.The following specification is for the pressure drop across the aftercooler core:Water pressure differential ... 9.6 kPa (1.4 psi)If the pressure drop across the core is out of specification, clean or replace the aftercooler core. Aftercooler Core Leakage
Typically, a leak from the coolant circuit of the aftercooler core can be found by performing a visual inspection of the core. Perform the following procedure:
Remove the