C-15 and C-16 Industrial Engines – Aftercooler – Test

Table 1
Tools Needed    
Part Number     Part Name     Quantity    
1U-5470     Engine Pressure Group     1    
FT-1984     Aftercooler Testing Group     1    

Visual Inspection

Inspect the following parts at each oil change:

  • Air lines

  • Hoses

  • Gasket joints

Pressurized air can cause personal injury. When pressurized air is used for cleaning, wear a protective face shield, protective clothing, and protective shoes.

Ensure that the constant torque hose clamps are tightened to the correct torque. Check the specifications for the correct torque. Check the welded joints for cracks. Ensure that the brackets are tightened in the correct positions. Ensure that the brackets are in good condition. Use compressed air to clean any debris or any dust from the aftercooler core assembly. Inspect the fins in the aftercooler core for the following conditions:

  • Damage

  • Debris

  • Corrosion

Use a stainless steel brush to remove any corrosion.

Note: When parts of the air-to-air aftercooler system are repaired or replaced, a leak test is recommended.

The use of winter fronts or shutters is discouraged with air-to-air aftercooled systems. Winter fronts can only be used on certain vehicle models. On these vehicles, tests have shown that the engine jacket water will overheat before the inlet manifold air temperature is excessive. These vehicles use sensors and indicators that are installed in order to indicate engine operating conditions before excessive inlet manifold air temperatures are reached.

Inlet Manifold Pressure

Normal inlet manifold pressure with high exhaust temperature can be caused by blockage of the fins of the aftercooler core. Clean the fins of the aftercooler core. Refer to “Visual Inspection” under this topic for the cleaning procedure.

Low inlet manifold pressure and high exhaust manifold temperature can be caused by any of the following conditions:

Plugged air cleaner – Clean the air cleaner or replace the air cleaner, as required. Refer to the Operation and Maintenance Manual, “Engine Air Cleaner Element – Clean/Replace”.

Blockage in the air lines – Blockage in the air lines between the air cleaner and the turbocharger must be removed.

Aftercooler core leakage – Aftercooler core leakage should be pressure tested. Refer to “Aftercooler Core Leakage” under this topic for the testing procedure.

Inlet manifold leak – An inlet manifold leak can be caused by the following conditions: loose fittings and plugs, missing fittings and plugs, damaged fittings and plugs and leaking inlet manifold gasket.

Aftercooler Core Leakage

Illustration 1 g00295702

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) Dust plug

(9) Chain

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


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.

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:

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

    Illustration 2 g00298658

    A typical example of the tooling that is installed is shown above.

    (1) Coupler

    (2) Chain

    (3) Dust plug

    Dust plug chains must be installed to the aftercooler core or to the radiator brackets to prevent possible injury while you are testing. Do not stand in front of the dust plugs while you are testing.

  1. Install couplers (1) on each side of the aftercooler core. Also, install dust plugs (3) .

    These items are included with the FT-1984 Aftercooler Testing Group .

    Note: Installation of additional hose clamps on the hump hoses is recommended in order to prevent the hoses from bulging while the aftercooler core is being pressurized.


    Do not use more than 240 kPa (35 psi) of air pressure or damage to the aftercooler core can be the result.

    Illustration 3 g00298678

    (5) Regulator and valve assembly.

  1. Install the regulator and valve assembly (5) on the outlet side of the aftercooler core assembly. Also, attach the air supply.
  1. Open the air valve and pressurize the aftercooler to 205 kPa (30 psi). Shut off the air supply.
  1. Inspect all connection points for air leakage.
  1. The pressure in the aftercooler system should not drop more than 35 kPa (5 psi) in 15 seconds.
  1. 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.

    To help prevent personal injury when the tooling is removed, relieve all pressure in the system slowly by using an air regulator and a valve assembly.

  1. 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

Pressure measurements should be taken at the inlet manifold and the turbocharger outlet.

Use the differential pressure gauge of the 1U-5470 Engine Pressure Group. Use the following procedure in order to measure the restriction of the aftercooler:

  1. Connect the vacuum port of the differential pressure gauge to a port on the inlet manifold.
  1. Connect the pressure port of the differential pressure gauge to a port on the turbocharger outlet.
  1. Record the value.

The air lines and the cooler core must be inspected for internal restriction when both of the following conditions are met:

  • Air flow is at a maximum level.

  • Total air pressure drop of the charged system exceeds 13.5 kPa (4 in Hg) for engines with a 14.6 L (890 in3) displacement.

  • Total air pressure drop of the charged system exceeds 15.2 kPa (4.5 in Hg) for engines with a 15.8 L (964 in3) displacement.

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

  • Clean

  • Repair

  • Replacement

Turbocharger Failure

Personal injury can result from air pressure.

Personal injury can result without following proper procedure. When using pressure air, wear a protective face shield and protective clothing.

Maximum air pressure at the nozzle must be less than 205 kPa (30 psi) for cleaning purposes.

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.


Do not use caustic cleaners to clean the air-to-air aftercooler core.

Caustic cleaners will attack the internal metals of the core and cause leakage.