C15 and C18 – Aftercooler – Test

Turbocharger Failure

If a turbocharger failure occurs, remove the air-to-air aftercooler core. Internally flush the air-to-air aftercooler core with a solvent that removes oil and other foreign substances. Shake the air-to-air aftercooler core in order to eliminate any trapped debris. Wash the aftercooler with hot, soapy water. Thoroughly rinse the aftercooler with clean water and blow dry the aftercooler with compressed air. Blow dry the assembly in the reverse direction of normal air flow. To make sure that the whole system is clean, carefully inspect the system.

Aftercooler Core Leakage

FT-1984 Aftercooler Testing Group

(1) Regulator and valve assembly

(2) Nipple

(3) Relief valve

(4) Tee

(5) Coupler

(6) Aftercooler

(7) Dust plug

(8) Chain

(9) Dust plug


A low-power problem in the engine can be the result of aftercooler leakage. Aftercooler system leakage can result in the following problems:

  • Low power
  • Low boost pressure
  • Black smoke
  • High exhaust temperature

A large leak of the aftercooler core can often be found by making a visual inspection. To check for smaller leaks, use the following procedure:

Disconnect the air pipes from the inlet and outlet side of the aftercooler core.

Install couplers (5) on each side of the aftercooler core. Also, install dust plugs (7) and (9). These items are included with the FT-1984 Aftercooler Testing Group.
Note: Installation of additional hose clamps on the hump hoses is recommended to prevent the hoses from bulging while the aftercooler core is being pressurized.

Install the regulator and valve assembly (1) on the outlet side of the aftercooler core assembly. Also, attach the air supply.

Open the air valve and pressurize the aftercooler to 205 kPa (30 psi). Shut off the air supply.

Inspect all connection points for air leakage.

The aftercooler system pressure should not drop more than 35 kPa (5 psi) in 15 seconds.

If the pressure drop is more than the specified amount, use a solution of soap and water to check all areas for leakage. Look for air bubbles that will identify possible leaks. Replace the aftercooler core, or repair the aftercooler core, as needed.

After the testing, remove the FT-1984 Aftercooler Testing Group. Reconnect the air pipes on both sides of the aftercooler core assembly.

Air System Restriction

Use the following procedure in order to measure the restriction of the aftercooler:

  1. Connect Caterpillar Electronic Technician (ET) to the ECM.
  1. Record channels “Aftertreatment #1 Secondary Air Pressure” and “Boost Pressure”.
  1. Run the engine at high idle speed.
  1. Record the values.
  1. Subtract the “Boost Pressure” value from the “Aftertreatment #1 Secondary Air Pressure” value. This value will be your total air pressure drop for the charged system.

The lines and cooler core must be inspected for restriction if the engine is operated at high idle with both of the following conditions:

  • Air flow is at a maximum level.
  • Total air pressure drop of the charged system exceeds 15 kPa (4.5 in Hg).

If a restriction is discovered, proceed with the following tasks, as required:

  • Clean
  • Repair
  • Replacement

Dynamometer Test

In hot ambient temperatures, chassis dynamometer tests for models with an air-to-air aftercooler can add a greater heat load to the jacket water cooling system. Therefore, the jacket water cooling system temperature must be monitored. The following measurements may also need a power correction factor:

  • Inlet air temperature
  • Fuel API rating
  • Fuel temperature
  • Barometric pressure

With dynamometer tests for engines, use the FT-1438 Aftercooler Gp (DYNAMOMETER TEST). This tool allows the water cooled aftercooler to control the inlet air temperature to 43 °C (110 °F).

Posted in C18

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