879979T 1 Mercury HARNESS ASSEMBLY, Tachometer (SC1000-3)

Visual Inspection
Inspect the following parts at each oil change:
Air lines
Hoses
Hose clamps
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 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 cooler core fins for the following conditions:
Damage
Debris
CorrosionUse a stainless steel brush to remove any corrosion. Ensure that you use soap and water.Note: When parts of the air-to-air aftercooler system are repaired, a leak test is recommended. When parts of the air-to-air aftercooler system are replaced, a leak test is recommended.Inlet Manifold Pressure
Normal inlet manifold air 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" 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" topic for the testing procedure.Leakage of the induction system - Any leakage from the pressure side of the induction system must be repaired.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) ChainA 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:
Disconnect the air pipes from the inlet and outlet side of the aftercooler core.
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.
Install couplers (5) on each side of the aftercooler core. Also, install dust plugs (7) and (8). 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.
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's 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.
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.
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
Illustration 2 g00581364
Pressure measurements should be taken at the inlet manifold (1) and at the turbocharger outlet (2) .Use the differential pressure gaug