Restriction Of Air Inlet And Exhaust
There will be a reduction in the performance of the engine if there is a restriction in the air inlet system or the exhaust system.
The air flow through a used air cleaner may have a restriction. The air flow through a plugged air cleaner will be restricted to some degree. In either case, the restriction must not be more than the following amount:
- 6.25 kPa (25 inches of H2O)
Back Pressure is the difference in the pressure between the exhaust at the outlet elbow and the atmospheric air. Back pressure from the exhaust must not be more than the following amount:
- 10 kPa (40 inches of H2O)
Measurement Of Pressure In Inlet Manifold
| Tools Needed | ||
|---|---|---|
| Part Number | Part Description | Qty |
| 1U-5470 | Engine Pressure Group | 1 |
The efficiency of an engine can be checked by making a comparison. Compare the pressure in the inlet cover and the information in the Technical Marketing Information (TMI).
This test is used when there is a decrease of horsepower from the engine, yet there is no actual sign of a problem with the engine.
The correct pressure for the inlet manifold is also given in the Technical Marketing Information (TMI), "Fuel Setting and Related Information". These standards are established under the following conditions:
- 96 kPa (29 inches of Hg) dry barometric pressure
- 29°C (85°F) outside air temperature
- 35 API rated fuel
Any change from these conditions can change the pressure in the inlet manifold. The outside air may have a higher temperature and a lower barometric pressure than the values that are given above. This will cause a lower inlet manifold pressure measurement than the pressure in the TMI. Outside air that has both a lower temperature and a higher barometric pressure will cause a higher inlet manifold pressure measurement.
A difference in fuel density will change horsepower (stall speed) and boost. If the fuel is rated above 35 API, the pressure in the inlet manifold can be less than the pressure that appears in the TMI. If the fuel is rated below 35 API, the pressure in the inlet manifold can be more than the pressure that appears in the TMI. BE SURE THAT THE AIR INLET OR THE EXHAUST DOES NOT HAVE A RESTRICTION WHEN YOU ARE MAKING A CHECK OF THE PRESSURE.
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| Illustration 1 | g00557590 |
Pressure Test Locations (A) Plugs | |
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| Illustration 2 | g00295554 |
1U-5470 Engine Pressure Group | |
The 1U-5470 Engine Pressure Group can be used to check the pressure in the inlet manifold.
The 1U-5470 Engine Pressure Group has a gauge that indicates pressure inside the inlet manifold. Refer to Special Instructions, SEHS8907 which is included with the engine pressure group for complete instructions.
Measurement Of Exhaust Temperature
| Tools Needed | ||
|---|---|---|
| Part Number | Part Description | Qty |
| 1U-8865 | Infrared Thermometer | 1 |
When the engine runs at low idle, the temperature of an exhaust manifold port can indicate the condition of a unit injector.
A low temperature indicates that no fuel is flowing to the cylinder. An inoperative unit injector pump could cause this low temperature.
A very high temperature can indicate that too much fuel is flowing to the cylinder. A malfunctioning unit injector could cause this very high temperature.
Use the 1U-8865 Infrared Thermometer to check this exhaust temperature. You can find operating instructions and maintenance instructions inside the Operator's Manual, NEHS0510, "1U-8865 Infrared Thermometer".
Air-to-Air Aftercooled Systems
| Tools Needed | ||
|---|---|---|
| Part Number | Part Description | Qty |
| FT-1984 | Air-to-Air Aftercooler Testing Group | 1 |
| FT-1438 | Dynamometer Testing Aftercooler | 1 |
Visual Inspection
Inspect the following components of the air-to-air aftercooler system:
- all lines
- all hoses
- all gasket joints
Make sure that the constant torque hose clamps are tightened to the correct torque. Check the truck manufacturer's specifications for the correct torque.
Check the welded joints for any cracks. Check the brackets for correct positioning. Also, make sure that these brackets are in good condition. Use compressed air to clean any debris or any dust from the aftercooler core assembly. Inspect the aftercooler core assembly's fins for the following conditions:
- damage
- debris
- salt corrosion
Use a stainless steel brush to remove any corrosion. Make sure that you use soap and water.
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Pressurized air can cause personal injury. When pressurized air is used for cleaning, wear a protective face shield, protective clothing, and protective shoes. |
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Note: When air-to-air aftercooler parts are repaired and air-to-air aftercooler parts are replaced, a leak test should be completed.
Do not use winter fronts and shutters with aftercooler systems. Winter fronts can only be used on certain truck models. The jacket water pumps on these models will overheat before the air temperature of the inlet manifold becomes excessive. These truck models use special alarms or other indicators. These instruments warn the operator about an engine overheating. Check with the manufacturer about the use of both winter fronts and shutters.
Air System Restriction
Periodically, take pressure measurements at the turbocharger outlet and at the inlet manifold. The air lines and the cooler core must be inspected for internal restriction under both of the following conditions:
- The air flow is at a maximum level.
- The total of the air pressure drop of the charged system has exceeded the following value: 13.5 kPa (4 Inches Hg)
If a restriction is discovered, proceed with the following tasks, as required:
- clean
- repair
- replacement
Turbocharger Failure
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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. |
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If a turbocharger failure occurs, remove the air-to-air aftercooler core. Flush the air-to-air aftercooler core internally with a solvent that removes oil and other foreign substances. Shake the aftercooler core assembly in order to remove any trapped debris. Wash the aftercooler core assembly with hot, soapy water. Thoroughly rinse this assembly with clean water, and then blow dry the assembly 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.
| NOTICE |
|---|
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. |
Inlet Manifold Pressure
Normal inlet manifold pressure with high exhaust temperature can be caused by blockage in the aftercooler core assembly's fins. Clean the aftercooler core assembly's fins. Refer to "Visual Inspection" for the correct 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, as required. Replace the air cleaner, as required.
Blockage in the air lines - Blockage in the air lines between the air cleaner and the turbocharger must be removed.
Aftercooler core leakage - An aftercooler core leakage should be pressure tested. See "Aftercooler Core Leakage" for the correct procedure to clean parts. Use the same manual for information on repairing parts and on replacing parts.
Leakage of the induction system - Any leakage from the pressure side of the induction system should be repaired.
Inlet manifold leak - An inlet manifold leak can be caused by both loose fittings and loose plugs. Missing fittings, missing plugs, damaged fittings, and damaged plugs can also cause these leaks. Finally, problems with the manifold to cylinder head gaskets can cause this same problem. Check all of these items.
Aftercooler Core Leakage
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| Illustration 3 | g00295702 |
Using FT1984 Air-to-Air Aftercooler Test Group (1) Regulator and valve assembly. (2) Nipple. (3) Relief valve. (4) Tee. (5) Coupler. (6) Aftercooler core assembly. (7) Dust plug. (8) Dust plug. (9) Chain. | |
Aftercooler leakage can cause the following conditions to occur:
- low engine power
- low boost pressure
- black smoke
- high exhaust temperature
| NOTICE |
|---|
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 in the aftercooler core can be found through a visual inspection. To check for smaller leaks, use the following procedure:
- Disconnect the air pipes from the inlet side of the aftercooler core assembly and from the outlet side of the aftercooler core assembly.
- Install couplers (1) on each side of the aftercooler core. Also, install dust plugs (3).
These items are included with the FT-1984 Air-to-Air Aftercooler Test Group .
Note: The installation of additional hose clamps on hump hoses is recommended. This additional installation should prevent the hump hoses from bulging while the aftercooler core is being pressurized.
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| Illustration 4 | g00298658 |
A typical example of the tooling that is installed is shown above. (1) Coupler. (2) Chain. (3) Dust plugs. | |
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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. |
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- Install the regulator and valve assembly (5) onto the outlet side of the aftercooler core assembly. Also, attach the air supply.
| NOTICE |
|---|
Do not use more than 240 kPa (35 psi) of air pressure or damage to the aftercooler core can be the result. |
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| Illustration 5 | g00298678 |
(5) Regulator and valve assembly. | |
- 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.
Note: If the pressure drop is more than the specified amount, use a solution of soap and of 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 you test the aftercooler core assembly, remove the FT1984 Air-to-Air Aftercooler Test Group. Reconnect the air pipes on both sides of the aftercooler core assembly.
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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. |
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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's temperature must be monitored. Also, monitor the inlet air temperature, which may need a power correction factor. These other measurements may also need a power correction factor:
- fuel API rating
- fuel temperature
- barometric pressure
Note: Refer to Special Instructions, LEBT3477, "Truck Performance And Driveability Diagnostic Guide" and Special Instructions, SEHS8025, "Using The Caterpillar Performance Analysis Report (PAR) Program For On-Highway Truck Engines". The Special Instructions will provide more detailed instructions concerning the preparation of the truck. The publications will also provide more detailed instructions concerning the proper use of the dynamometer.
With dynamometer tests for engines, use the FT1438 Dynamometer Testing Aftercooler. This tool provides an air to a water cooled aftercooler. The tool controls the inlet air temperature to a temperature of 43°C (109°F).
Crankcase (Crankshaft Compartment)
| Tools Needed | ||
|---|---|---|
| Part Number | Part Description | Qty |
| 8T-2700 | Blowby/Air Flow Indicator | 1 |
Pistons or rings that have damage can be the cause of too much pressure in the crankcase. This condition will cause the engine to run rough. There will be more than the normal amount of fumes rising from the crankcase breather. This crankcase pressure can also cause the element for the crankcase breather to have a restriction in a very short time. This crankcase pressure can also be the cause of any oil leakage at the gaskets and at the seals. These areas would not normally have leakage.
Note: The electronic service tool (ET) can be used to measure crankcase pressure.
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| Illustration 6 | g00286269 |
8T-2700 Blowby/Air Flow Indicator | |
The 8T-2700 Blowby/Air Flow Indicator checks the amount of blowby. See Special Instructions, SEHS8712 for more information on using this tool.
Compression
An engine that runs roughly can have a leak at the valves. An engine that runs roughly can also have valves that need an adjustment. Remove the cylinder head and inspect the valves and valve seats. Removal of the cylinder head is sometimes necessary in order to find small defects. Repairs are normally done when the engine is being reconditioned.
Cylinder Heads
The cylinder heads consist of three main components that can be removed:
- valve seat inserts
- valve guides
- bridge dowels
When any of these components are worn or when these components are damaged, these components can be removed. Refer to Disassembly and Assembly for the replacement of these components.
Valves
The following tools make removing and installing the valves easier:
Valve Seat Inserts
The 166-7441 Valve Seat Extractor Tool is needed in order to remove the valve seat inserts. The 166-7441 Valve Seat Extractor Tool is also needed to install the valve seat inserts. Refer to Special Instruction, SMHS7935 for an explanation on the removal procedure for the valve seat inserts. For easier installation, lower the temperature of the insert before the insert is installed in the head.
Valve Guides
The following tools are needed in order to remove the valve guides:
The tools are also used to install the valve guides.
The counterbore in the driver bushing installs the valve guide to the correct height. After the installation of the valve guide in the head, use a 1P-7451 Valve Guide Honing Group in order to make a finished bore in the valve guide. Refer to Special Instruction, SMHS7526 for an explanation on this procedure. Grind the valves after the new valve guides are installed.
Checking Valve Guide Bores
Use the 5P-3536 Valve Guide Gauge Group to check the bore of the valve guides. Refer to Special Instruction, GMG02562 for detailed instructions on the use of the 5P-3536 Valve Guide Gauge Group .
Bridge Dowel
Use a 5P-0944 Dowel Puller Group with a 5P-0942 Dowel Extractor to remove the bridge dowels. Install a new bridge dowel with a 5P-2406 Dowel Driver. This dowel driver installs the bridge dowel to the correct height.
Bridge Adjustment
When the head is disassembled, keep the bridges with the same cylinders. Adjustment of the bridge will be necessary after the valves are ground or other reconditioning of the cylinder head is done. Whenever the valves are adjusted, the bridges should be checked and/or adjusted. Use the following procedure to make an adjustment to the bridge:
Note: The valves must be fully closed.
- Put engine oil on the bridge dowel in the cylinder head and in the bore in the bridge.
- Install the bridge with the adjustment screw toward the exhaust manifold.
- Loosen the locknut for the adjustment screw. Loosen the adjustment screw.
- Put a light force on the bridge in order to keep the bridge in contact with the valve stem that is opposite the adjustment screw. Refer to Figure 7.
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| Illustration 7 | g00555807 |
- Turn the adjustment screw clockwise until the screw just makes contact with the valve stem. Turn the adjustment screw in the clockwise direction for 30 degrees. This straightens the bridge on the dowel. This also compensates for the clearance in the threads of the adjustment screw.
- Hold the adjustment screw in this position. Tighten the locknut to 30 ± 4 N·m (22 ± 3 lb ft).
- Put engine oil on the contact point between the rocker arm and the bridge.
Valve Lash Setting
Valve lash is measured between the rocker arm and the valve bridge. All of the clearance measurements and the adjustments must be made with the engine stopped. The valves must be FULLY CLOSED.
| Valve Lash | |
| Valves | Acceptable Range for Valve Lash |
| Inlet | 0.38 ± 0.08 mm (.015 ± .003 inch) |
| Exhaust | 0.76 ± 0.07 mm (.030 ± .003 inch) |
Note: An adjustment is not necessary if the measurement of the valve lash is in the acceptable range. Refer to 5 for the acceptable range. If the measurement is outside this range, an adjustment is necessary. The following procedure gives the correct procedure to adjust the valve lash.
| Valve Lash | |
| Valves | Gauge Dimension |
| Inlet | 0.38 mm (.015 inch) |
| Exhaust | 0.76 mm (.030 inch) |
- Put the No. 1 piston at the top center position.
Note: If the engine is equipped with an engine compression brake, loosen the adjusting screw for the engine compression brake slave piston lash prior to adjusting the engine valve lash. Refer to the Testing and Adjusting, "Compression Brake" topic in order to adjust the slave piston lash.
Note: See Testing and Adjusting, "Finding Top Center Position for No. 1 Piston" for further details.
- With No. 1 piston at the top center position of the compression stroke, an adjustment can be made to the valves.
Before any adjustments are made, lightly tap each rocker arm at the top of the adjustment screw. Use a soft mallet to ensure that the lifter roller seats against the camshaft's base circle.
- Make an adjustment to the valve lash on the inlet valves for cylinders 1, 2, and 4.
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| Illustration 8 | g00284836 |
Cylinder and Valve Location | |
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| Illustration 9 | g00555816 |
- Make an adjustment to the valve lash on the exhaust valves for cylinders 1, 3, and 5.
- After each adjustment, tighten the nut for the valve adjustment screw to 30 ± 4 N·m (22 ± 3 lb ft).
- Remove the top center bolt, and turn the flywheel by 360 degrees in the direction of the engine's rotation. This will position the No. 6 piston at the top center on the compression stroke. Install the top center bolt in the flywheel.
- Make an adjustment to the valve lash on the inlet valves 3, 5, and 6.
- Make an adjustment to the valve lash on the exhaust valves 2, 4, and 6.
- After each adjustment, tighten the nut for the valve adjustment screw to 30 ± 4 N·m (22 ± 3 lb ft).
- Remove the top center bolt from the flywheel after all valve lash adjustments have been made.
Refer to the Testing and Adjusting, "Compression Brake" topic for information on adjusting the slave piston lash.