3508, 3512 and 3516 Engines Caterpillar

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 the air cleaner may have a restriction. The restriction must not be more than 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 6.75 kPa (27 inches of H₂O).

Measurement Of Pressure In Inlet Manifold

The efficiency of an engine can be checked. Compare the pressure in the inlet manifold with the specifications that are given in the Fuel Setting and Related Information in the TMI (Technical Marketing Information). This test is used when there is a decrease in horsepower from the engine, yet there is no real sign of a problem with the engine.

The correct pressure for the inlet manifold is given in the TMI. Development of this information is done with these conditions:

• 96 kPa (28.8 inches of Hg) dry barometric pressure

• 29°C (84°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 horsepower and a lower inlet manifold pressure measurement than the pressure that is given in the TMI (Technical Marketing Information). Outside air that has a lower temperature and a higher barometric pressure will cause a higher horsepower and a higher inlet manifold pressure measurement.

A difference in fuel rating will change horsepower and the pressure in the inlet manifold. If the fuel is rated above 35 API, the pressure in the inlet manifold can be less than the pressure that is given in the TMI. If the fuel is rated below 35 API, the pressure in the inlet manifold can be more than the pressure that is given 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 IN THE INLET MANIFOLD.

Illustration 1	g00322855
Pressure Test Location (Typical Example) (A) Pipe plug.

In order to check the inlet manifold pressure, remove the 1/2-14-NPTF pipe plug (A). Connect the 1U-5470 Engine Pressure Group to this opening in the inlet manifold.

This tool group has a gauge to read pressure in the inlet manifold. Special Instruction, SEHS8524 is with the tool group and gives the instructions.

Illustration 2	g00284796
1U-5470 Engine Pressure Group (1) Pressure indicators. (2) Zero adjustment screw. (3) Pressure indicator. (4) Pressure tap. (5) Pressure indicator.

Measurement Of Exhaust Temperature

Use the 1U-8865 Infrared Thermometer in order to check the exhaust temperature. The Operating Manual, NEHS0510 for the 1U-8865 Infrared Thermometer gives complete operating and maintenance instructions for this tool.

Individual cylinder head exhaust temperatures can be checked with the 4C-6090 Temperature Selector Group, the 6V-9130 Temperature Adapter, and the 6V-7070 Digital Multimeter. Refer to Operating Manual, NEHS0537 for the complete operating instructions for the 4C-6090 Temperature Selector Group .

Crankcase (Crankshaft Compartment)

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 coming 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 that would not normally have leakage.

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. Removal of the head and inspection of the valves and valve seats is necessary to find those small defects that do not normally cause a problem. Repairs of these problems are normally done when you are reconditioning the engine.

Cylinder Heads

The cylinder heads have valve seat inserts, valve guides, and bridge dowels that can be removed when the parts are worn or damaged. Refer to Disassembly And Assembly for the replacement of these components.

Valves

The removal and the installation of the valves is easier with use of the 1P-3527 Valve Spring Compressor .

Valve Seat Inserts

Use the 6V-4805 Valve Seat Extractor Tool Group for the removal and the installation of the valve seat inserts. Lower the temperature of the insert before the inset is installed in the head.

Valve Guides

The tools for the removal and the installation of the valve guides are the 5P-1729 Valve Guide Driver Bushing and the 7M-3975 Valve Guide Bushing Driver. The counterbore in the driver bushing installs the guide to the correct height. Use a 1P-7451 Valve Guide Honing Group in order to make a finished bore in the valve guide after the guide is installed in the head. Refer to Special Instruction, SMHS7526 for an explanation for this procedure. Grind the valves after the new valve guides are installed.

Checking Valve Guide Bores

Use the 5P-3536 Valve Guide Gauge Group in order to check the bore of the valve guides. Refer to Special Instruction, GMG02562 for the instructions for the use of this tool.

Illustration 3	g00285313
5P-3536 Valve Guide Gauge Group

Bridge Dowels

Use a 5P-0944 Dowel Puller Group and a 5P-0942 Dowel Extractor. Remove the bridge dowels. Install a new bridge dowel with a 6V-4009 Dowel Driver. This dowel driver installs the bridge dowel to the correct height.

Valve Lash

Valve lash is measured between the rocker arm and the bridge for the valves. All of the clearance measurements and the adjustments must be made with the engine stopped. The valves must be FULLY CLOSED.

Valve Lash Check

An adjustment is NOT NECESSARY if the measurement of the valve lash is in the acceptable range. The range is given in Table 1.

If the measurement is not within this range adjustment is necessary. See Testing And Adjusting, "Valve Lash And Valve Bridge Adjustment".

Valve Lash And Valve Bridge Adjustment

Illustration 4	g00286271
147-5482 Indicator Gauge Group (1) 147-2060 Wrench. (2) 147-2059 Torque Wrench. (3) 148-7211 Bridge Nut Socket. (4) 145-5191 Gauge Support Assembly. (5) 147-2056 Dial Indicator. (6) 147-5536 Indicator Contact Point. (7) 147-2057 Indicator Contact Point. (8) 147-2058 Indicator Extension .

Note: The 145-5191 Gauge Support Assembly (4), 147-2057 Indicator Contact Point (7), 147-2058 Indicator Extension (8) and 147-5536 Indicator Contact Point (6) are included in the 147-5482 Indicator Gauge Group.

Note: The 147-2056 Dial Indicator or the 147-5537 Dial Indicator (Metric, not shown) can be used with the 147-5482 Indicator Gauge Group.

Valve Bridge Adjustment

Note: When using the 147-5482 Indicator Gauge Group it is not necessary for you to remove the rocker arm shaft assemblies. The valves must be fully closed when the adjustment is made. Refer to Systems Operation, Testing And Adjusting, "Finding Top Center Position For No. 1 Piston"

Installation

1. Assemble the 147-2058 Indicator Extension and the 147-5536 Indicator Contact Point on the 147-2056 Dial Indicator or on the 147-5537 Dial Indicator .

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Illustration 5	g00286279
145-5191 Gauge Support Assembly. (1) Knurled knob.

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Illustration 6	g00286280
(2) Valve cover base rear bolt hole.

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Illustration 7	g00286281
(3) 147-5536 Indicator Contact Point. (4) Top edge of the valve bridge.

2. Install the 145-5191 Gauge Support Assembly in the rear bolt hole (2). The rear bolt hole is located in the valve cover base. Adjust the contact point (3) on the top edge of the valve bridge (4) .

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Illustration 8	g00286283
(5) Adjustment screw.

3. Loosen the locknut for the adjustment screw. Loosen the adjustment screw (5) several turns.

4. Apply a force of 5 N (1 lb) to 45 N (10 lb). Push down on the top contact surface of the valve bridge. Zero the indicator.

5. Turn the adjustment screw (5) clockwise until the dial indicator reads .038 mm (0.0015 inch). The correct measurement is equal to turning the adjustment screw 20 to 30 degrees after the screw contacts the end of the valve.

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Illustration 9	g00286364
(6) 148-7211 Bridge Nut Socket.

6. Hold the adjustment screw with the 148-7211 Bridge Nut Socket (6) in order to tighten the locknut to 30 ± 4 N (22 ± 3 lb). You may use a sliderule torque computer in order to determine the torque wrench dial reading for the different extensions. Refer to Special Instruction, SEHS7150 July 1991, "Snap On Torque Computer".

Valve Lash Adjustment

Note: The valve bridges MUST be adjusted before making the valve lash adjustments.

1. Ensure that the number 1 piston is at the top center position. Refer to Systems Operation, Testing And Adjusting, "Finding Top Center Position For No. 1 Piston"

2. The number 1 piston should be at the top center position of the correct stroke. Make adjustments to the valves as shown in the chart: Refer to Systems Operation, Testing And Adjusting, "Crankshaft Positions For Unit Injector Adjustment And Valve Lash Setting"

   Note: Tap each rocker arm on the top of the adjustment screw before making any adjustments. Use a soft hammer. Make sure that the lifter roller is seated against the base circle of the camshaft.

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Illustration 10	g00286365
(1) 145-5191 Gauge Support Assembly. (2) 147-2057 Indicator Contact Point.

3. Install the 145-5191 Gauge Support Assembly (1). Use the 147-2056 Dial Indicator or use the 147-5537 Dial Indicator. Use the 147-2057 Indicator Contact Point (2). Install the tool in the rear bolt hole. The rear bolt hole is located on the valve cover base.

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Illustration 11	g00286366
(3) 147-2060 Wrench. (4) 147-2059 Torque Wrench.

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Illustration 12	g00286367
(3) 147-2060 Wrench. (4) 147-2059 Torque Wrench.

4. Move the rocker assembly upward and move the rocker arm assembly downward. Move the rocker assembly several times. The oil film is removed in order to get a true zero reading on the dial indicator. Use the 147-2060 Wrench (3) and use the 147-2059 Torque Wrench (4). Install the socket wrench and install the torque wrench on the nut of the rocker arm. Apply upward pressure to the front of the rocker assembly. Set the dial indicator to zero. The weight of the torque wrench (4) allows the valve lash to be read. Do not apply any pressure on the torque wrench.

5. Loosen the locknut. The locknut is located on the adjustment screw of the push rod. Turn the adjustment screw until the valve lash is set to specifications. Tighten the nut for the adjustment screw to 70 ± 15 N·m (50 ± 11 lb ft ). The 147-2059 Torque Wrench is preset to the torque that is required. Check the adjustment again.