MIDLAND AIR COMPRESSORS Caterpillar

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NOTICE
The safe and reliable operation of all motor vehicles depends on proper service and repair procedures. The procedures recommended and described in this manual are effective methods for performing service operations. This manual contains information which should be followed to minimize the risk of personal injury to service personnel or damage to vehicles through unsafe service procedures. This information does not cover all the possible service hazards. Accordingly, anyone using a service procedure or tool not recommended must first be satisfied that their safety or the vehicle's safety will not be jeopardized by the method selected.

General Description

The EL-1300 and EL-1600 Air Compressors are water-cooled, two cylinder, reciprocating piston-type air compressors that are designed for high performance with maximum durability for extended life. They can be base or flange mounted. The air compressor is an air pump that fills an air supply tank with compressed air. The crankshaft in the air compressor is driven by the engine and the air compressor operates when the engine is running.

Air Compressor Operation

The EL-1300 and EL-1600 Air Compressors are identical except for the crankshaft stroke, the rated displacement, and the height.

EL-1300 Air Compressor

* The stroke is 38.1 mm (1.50 in).

* The rated displacement (at 1250 rpm) is 12.9 cubic feet per minute.

EL-1600 Air Compressor

* The stroke is 47.5 mm (1.87 in).

* The rated displacement (at 1250 rpm) is 16.1 cubic feet per minute.

* The height of the EL-1600 Air Compressor is greater by 4.8 mm (.19 in) when compared to the height of the EL-1300 Air Compressor.

Two Cylinder EL-1300 Air Compressor

(1) Coolant outlet (to the engine cooling system).

(2) Air outlet (to the air supply tank).

(3) Cover over unloader valves.

(4) Cylinder head.

(5) Coolant inlets, either one (coolant from engine cooling system).

(6) Air inlet (from inlet air manifold of the engine).

(7) Cylinder block.

(8) Passage (to the top of each unloader valve in the cylinder head).

(9) Crankcase.

Two Cylinder EL-1600 Air Compressor (Side View and Top View)

(1) Coolant outlet (to the engine cooling system).

(2) Air outlet (to the air supply tank).

(3) Cover over unloader valves.

(4) Cylinder head.

(5) Coolant inlet (coolant from engine cooling system).

(6) Air inlet (from inlet air manifold of the engine).

(7) Cylinder block.

(8) Passage (to the top of each unloader valve in the cylinder head).

(9) Crankcase.

Coolant from the engine enters coolant inlet (5). Coolant inlet (5) on some air compressor installations is in cylinder head (4). The coolant from the air compressor flows through coolant outlet (1) and to the engine cooling system. The engine water pump moves the coolant through the air compressor when the engine is running.

Cylinder Head, Air Inlet Section

(10) Inlet valve.

(11) Unloader valve.

(12) Spring.

Cylinder Head, Air Outlet Section

(13) Outlet valve.

(14) Outlet valve stop.

(15) Spring.

The lubricating oil pump for the engine forces compressed oil through a passage in the air compressor crankshaft to each of the connecting rod journals of the crankshaft. The lubricating oil flows from the air compressor crankcase through holes and into the timing gear housing of the engine.

There are two inlet valves (10), two unloader valves (11) and two outlet valves (13) in cylinder head (4) of the air compressor. Each piston in cylinder block (7) has one each of the three valves. The air compressor cylinder head (4) gets filtered air from the engine air inlet manifold through a line that connects to air inlet (6).

When the crankshaft of the air compressor is turned, the two pistons move up and down in the cylinder block. When a piston goes down, the pressure of the air in the cylinder head is greater than the pressure of the air in the piston cylinder. The pressure of the air in the cylinder head now opens inlet valve (10) and goes into the piston cylinder.

As a piston goes up the pressure of the air in the piston cylinder increases. The pressure of the air and spring (12) now closes inlet valve (10). The piston moves further up and the pressure of the air in the piston cylinder increases until the air has more force than both spring (15), that keeps outlet valve (13) closed, and the pressure of the air in the other compartment in cylinder head (4). The high pressure of the air from the piston opens outlet valve (13), goes through the compartment in the cylinder head and through air outlet (2) that goes to the air supply tank.

An air compressor governor, that senses the amount of air (pressure), is installed on cylinder head (4) over passage (8) that goes to unloader valves (11).

Governor Operation (Midland)

Air Compressor Governor
(Valve Cap Assembly in Cut-in Position)

(1) Springs.

(2) Passage (in outlet housing).

(3) Air outlet (to unloader valves in cylinder head).

(4) Valve cap assembly.

(5) Diaphragm valve.

(6) Spring.

(7) Passage (in inlet housing).

(8) Air chamber.

(9) Air inlet and filter (air from supply tank).

Air Compressor Governor
(Valve Cap Assembly in Cut-out Position)

(1) Springs.

(2) Passage (in outlet housing).

(3) Air outlet (to unloader valves in cylinder head).

(4) Valve cap assembly.

(5) Diaphragm valve.

(6) Spring.

(7) Passage (in inlet housing).

(8) Air chamber.

(9) Air inlet and filter (air from supply tank).

Cylinder Head, Air Inlet Section (Inlet Valve Open)

(10) Inlet valve.

(11) Unloader valve.

(12) Spring.

The air compressor governor can be installed on the cylinder head of the air compressor or can be remote mounted. Air outlet (3) is in alignment with the passage, in the cylinder head, that goes to the top of each unloader valve (11).

The compressed air from the supply tank, through a line that is connected to the air inlet and filter (9), is kept in passage (7) by diaphragm valve (5). Springs (1) and spring (6) keep the diaphragm valve against the inlet housing of the governor.

The pressure (force) of the air, from the supply tank in passage (7) against diaphragm valve (5), increases as the air compressor puts more air in the tank. When the pressure of the supply tank air has more force than the force of springs (1) and spring (6), the air moves diaphragm valve (5) and valve cap assembly (4). When the diaphragm valve moves, the high compressed air in passage (7) goes into air chamber (8) and the air then moves valve cap assembly (4) against the output housing. The compressed air in air chamber (8) goes past spring (6) and through small orifices in the flange of valve cap assembly (4) into passage (2). The compressed air in passage (2) is also through air outlet (3) and is in the chamber of the top of each unloader valve (11) in the cylinder head. The pressure of the air in both passage (2) and passage (7) is the same and, with the same air pressure on both sides of diaphragm valve (5), spring (6) moves the diaphragm valve against the inlet housing.

The compressed air kept in passage (2) by diaphragm valve (5) and in the chamber at the top of each unloader valve (11) moved the unloader valves which opened each inlet valve (10).

The pistons cannot push air through the outlet valve when inlet valve (10) is open. The movement of the pistons lets air move freely in and out of the cylinder head and piston cylinder through inlet valve (10) that cannot close.

The air supply tank pressure (and the pressure of the air in the inlet passage of the governor) decreases as the air is used for the components on the vehicle. When the pressure of the air in the supply tank and in passage (7) decreases to cut-in pressure, the compressed air in passage (2) moves the outside edges of diaphragm valve (5) enough to let the compressed air move from passage (2) and air chamber (8) into passage (7). Now, the pressure (force) of the air in air chamber (8) on valve cap assembly (4) is less than the force of springs (1) so the springs move the valve cap assembly away from the outlet housing and against diaphragm valve (5).

(3) Air outlet (to unloader valves in cylinder head).

(9) Air inlet and filter (air from the supply tank).

(13) Exhaust hole.

(14) Adjusting screw.

When valve cap assembly (4) is not against the outlet housing, air from the chamber over unloader valve (11) goes into passage (2) and into the chamber for springs (1). The air in the chamber for springs (1) goes through a small exhaust hole (13). With no compressed air in the chamber over unloader valve (11) the spring moves the unloader valve away from inlet valve (10). When the inlet valve operates, the pistons again push air into the supply tank until the pressure of the air increases to cut-out pressure.

The cut-out pressure setting of the governor can be changed. Turn adjusting screw (14) to change the cut-out pressure setting. The cut-in pressure setting also changes when adjusting screw (14) is turned. The cut-in pressure is approximately 170 kPa (25 psi) less than the cut-out pressure setting.

Governor Operation (Bendix)

Air Compressor Governor (Piston in Cut-out Position)

(1) Pressure setting spring.

(2) Piston.

(3) Exhaust stem.

(4) Passage.

(5) Inlet and exhaust valve.

Air Compressor Governor (Piston in Cut-in Position)

(1) Pressure setting spring.

(2) Piston.

(3) Exhaust stem.

(4) Passage.

(5) Inlet and exhaust valve.

Cylinder Head, Air Inlet Section (Inlet Valve Open)

(6) Inlet valve.

(7) Unloader valve.

(8) Spring.

Some Midland Air Compressors, as used on Caterpillar equipment, have a Bendix governor. The main components of this governor are pressure setting spring (1), piston (2), exhaust stem (3), and inlet and exhaust valve (5).

Compressed air from the supply tank goes through the passage at the bottom of the governor. This air pressure is felt against the bottom of piston (2). The piston and inlet and exhaust valve (5) move up as the air pressure in the tank increases.

When the tank air pressure increases to the cut-out setting, exhaust stem (3) will lift inlet and exhaust valve (5) off its seat. This lets compressed air from the supply tank go through passage (4) and then through the outlet to the air compressor unloader valves.

The compressed air moves unloader valve (7) down. This opens inlet valve (6). When the inlet valve for each piston is open, there can be no compression of air. The air from the pistons can move freely through the open inlet valves and through the cylinder head.

The air pressure in the supply tank decreases as the air is used for the components on the vehicle. When the air pressure in the supply tank (and against the governor piston) decreases to the cut-in pressure, pressure setting spring (1) will move piston (2) down. The piston movement closes inlet and exhaust valve (5).

The piston moves until the compressed air at the top of unloader valve (7) can go back through passage (4). The air can flow from passage (4), through the center of exhaust stem (3) and then through the exhaust port.

With no air pressure in the chamber over unloader valve (7), the spring will move the unloader valve away from the inlet valve. This lets the inlet valve to operate normally and compression of air starts again.

Disassembly And Assembly

Cylinder Head

Remove Cylinder Head (11-1803)

1. Remove six bolts (2) from cylinder head (1).

2. Place marks (4) on cylinder head (1), cylinder block (3) and crankcase (5). The location for these parts must not change when the air compressor is assembled.

3. It may be necessary to hit cylinder head (1) with a soft hammer to remove the cylinder head from cylinder block (3).

Install Cylinder Head (12-1803)

1. Clean the valve surface of cylinder head (1).

2. Clean the surface of cylinder block (3).

3. Install cylinder head (1) with a new head gasket.

4. The long head bolt is through the cover for the unloader valves.

5. Tighten cylinder head bolts (2), in the numbered sequence, with a torque of 24 to 28 N·m (18 to 22 lb ft). Tighten the cylinder head bolts again in the same numbered sequence to a torque of 27 to 33 lb ft (38 to 34 N·m).

6. Torque for the two small bolts in the cover over the unloader valves is 11 to 17 N·m (100 to 150 lb in).

Disassemble Cylinder Head (15-1803)

start by:

a) Remove the cylinder head.

Remove cover (1) from the cylinder head.

2. Remove unloader valve (2) and spring (3).

3. Use a Kent-Moore #J-25447 tool (4) and remove cage (9). Remove spring (7), inlet valve (8) and valve seat (5) (both inlet valves).

4. Remove washer (6). Use a new washer under each valve seat at assembly.

5. Remove cage (14), exhaust valve (12) and spring (13). Remove exhaust valve stop (11), if necessary (both exhaust valves).

6. Remove washer (10). Use a new washer under each cage at assembly.

Assemble Cylinder Head (16-1803)

1. Install a new washer (1) for each exhaust valve.

2. Install exhaust valve stop (2).

3. Install spring (3), exhaust valve (4) and cage (5). Tighten the cage to a torque of 95 to 120 N·m (70 to 90 lb ft) for both exhaust valves.

4. Install a new washer (6) for each inlet valve.

5. Install valve seat (7), inlet valve (8), spring (9) and cage (10). Use a Kent-Moore #J-25447 tool (11) to tighten cage (10) to a torque of 95 to 109 N·m (70 to 80 lb ft) for both inlet valves.

6. Install spring (12) and the spring for the other unloader valve.

7. Install a new V-seal (13) on unloader valve (14). Apply plenty of 4L-7464 Grease-Silicone on the V-seal and the end of the unloader valve [a 12.7 mm (1/2 inch) bead of silicone grease on both seals].

8. Install the unloader valves, a new gasket (15) and cover (16).

end by:

a) Install the cylinder head.

Pistons And Connecting Rods

Remove Pistons And Connecting Rods (11-1803)

NOTE: An oversized 0.50 mm (.020 in) piston and connecting rod assembly is available.

NOTE: An undersized 0.25 mm (.010 in) connecting rod bearing assembly kit and an undersized 0.51 mm (.020 in) connecting rod bearing assembly kit is available.

start by:

a) Remove the cylinder head.

1. Remove bolts (1) and bottom cover (2).

NOTE: Some air compressors have a drain in the bottom cover.

2. Turn the crankshaft and look for the alignment arrows (5) on the connecting rods and the connecting rod bearing caps.

NOTE: Make a record to indicate which end the crankshaft arrows (5) face, and which piston and connecting rod is number one and number two. They must be installed in the same locations they were removed.

3. Remove bolts (3) and connecting rod cap (4). Turn the crank enough to push piston (6) to the top of the cylinder block and remove the piston and connecting rod.

NOTE: Place connecting rod cap (4) and bolts (3) in the connecting rod until they are to be installed on the crankshaft.

4. Remove snap ring (7) and press pin (8) out of piston (6).

5. Remove rings (9) from the piston.

6. Remove the cylinder block from the crankcase.

NOTE: The piston diameter, measured 90 degrees from the piston pin, must not be 0.20 mm (.008 in) less than the bore in the cylinder block. The bore at the top of the cylinder block can not be more than 0.03 mm (.001 in) larger than the bore at the bottom of the cylinder block.

Install Pistons And Connecting Rods (12-1803)

1. Place each piston ring in the bore of cylinder block (1) approximately 38 mm (1.5 in) from the top. Use a thickness gauge (2) to measure the ring end gaps for a 69.85 mm (2.750 in) bore.

For compressors built 1994 and before, compression ring (3) end gap is 0.18 to 0.43 mm (.007 to .017 in), oil ring (5) end gap is 0.25 to 1.02 mm (.010 to .040 in).

For compressors built 1995 and later, compression ring (3) end gap is 0.08 to 0.28 mm (.003 to .011 in), oil ring (5) end gap is 0.15 to 0.66 mm (.006 to .026 in).

2. Press pin (7) into the piston and connecting rod. Install snap ring (8).

3. Use a piston ring installation tool to install the rings on the pistons. Compression rings (3) have "TOP" or dots to indicate the surface of the ring that must face the top of the piston. Side clearance (4), for compression rings, is 0.013 to 0.074 mm (.0005 to .0029). Side clearance (6), for oil rings, is 0.013 to 0.165 mm (.0005 to .0065 in).

4. Install cylinder block (1), with a new gasket, on the crankcase. (The marks placed on the crankcase and block must be in alignment.) Tighten the two center bolts to a torque of 11 N·m (8 lb ft), then tighten the other four bolts to the same torque. Next, tighten the two center bolts to a torque of 23 to 26 N·m (17 to 21 lb ft), tighten the other four bolts to the same torque.

5. Use a ring compressor and install the connecting rods and pistons through the top of cylinder block (1). Ensure each piston and connecting rod are in the same location in the cylinder block and crankcase as before they were removed. Install bearing caps (9) on the connecting rods with the point of each arrow, on the bearing cap, toward the point of the arrow, on each connecting rod. Torque for bolts (10) is 21 to 26 N·m (185 to 225 lb in).

6. Install bottom cover (11). Torque for bolts (12) is 13 to 17 N·m (110 to 150 lb in).

end by:

a) Install the cylinder head.

Crankshaft

Remove Crankshaft (11-1803)

start by:

a) Remove the cylinder head.

b) Remove the pistons, connecting rods, and cylinder block.

1. Remove four bolts (1) and bearing cap (2).

NOTE: The bearing cap on some air compressors does not have oil line connections.

2. Remove the crankshaft (3) through the opening where bearing cap (2) was removed.

NOTE: If the bearing cap has a seal and spring, check the condition of the seal. If scratches in the seal are more than 0.13 mm (.005 in) deep, replace the seal.

3. Check the condition of crankshaft (3) connecting rod bearing journals. Damaged journals are ground smooth and undersize bearing inserts are installed in the connecting rods.

4. Check the condition of the main bearings (4). A damaged bearing must be removed.

Install Crankshaft (12-1803)

1. When it is necessary to install a new main bearing (1), heat the main bearing in oil to a temperature of not over 175°C (350°F) and immediately place the main bearing on crankshaft (2).

NOTE: The main bearing must be against the shoulder of the crankshaft.

2. Install the crankshaft and main bearings in the crankcase (3). Main bearing (1) must extend 3.5 mm (.14 in) from crankcase (3).

3. Install bearing cap (4). Tighten bolt (5) to a torque of 9 N·m (80 lb in). Then tighten bolt (6) and, afterwards, the other two bolts to the same torque.

4. Tighten bolt (5) to a torque of 14 to 18 N·m (120 to 160 lb in), tighten bolt (6) and then the other two bolts to the same torque.

end by:

a) Install the cylinder block pistons and connecting rods.

b) Install the cylinder head.

Air Compressor Governor (Midland)

Disassemble Governor (15-1804)

1. Remove the governor from the air compressor.

2. There are three springs, in compression, in the governor. Have a support on outlet housing (2) so the springs cannot push the outlet housing into the air. Then remove four bolts (1).

3. Remove adjusting screw (3), if necessary.

4. Clean springs (4), (5) and (7), outlet housing (2), inlet housing (10) and inlet filter (8) in an acceptable solvent. Inspect the parts for damage.

NOTE: It is a recommendation that new replacements be made for the valve cap assembly (6), diaphragm valve (9) and the O-rings on inlet filter (8) and inlet housing (10).

Assemble Governor (16-1804)

1. Place new O-rings on inlet housing (8) and inlet filter (9).

2. Place springs (3) and (4) in outlet housing (2).

NOTE: If adjusting screw (1) was removed, inner spring (4) and the adjusting screw can be installed after the governor is assembled.

3. Place spring (6) on a new valve cap assembly (5) and place a new diaphragm valve (7) on the spring. The diaphragm valve and spring must move freely on the valve cap assembly.

4. Place the valve cap assembly with the spring and diaphragm on springs (3) and (4).

5. Place inlet housing (8) on the valve cap assembly, spring and diaphragm. Use an adjustable clamp to move inlet housing (8) near outlet housing (2). Install four bolts (10). Torque for the bolts is 3.4 to 6.8 N·m (30 to 60 lb in).

NOTE: As inlet housing (8) moves into outlet housing (2), ensure the O-ring on the inlet housing does not get damaged when the housings join together.

6. Install inlet filter (9) with a torque of 3.4 to 6.8 N·m (30 to 60 lb in).

7. Install the air compressor governor on the air compressor. Torque for the screws is 13 to 17 N·m (110 to 150 lb in).

Air Compressor Governor (Bendix)

Disassemble Governor (15-1804)

1. Remove the governor from the air compressor.

2. Remove the rubber cover from governor body (3).

3. Use snap ring pliers to remove snap ring (1). Pull adjusting screw and spring assembly (2) from the body.

4. Remove the nut and washer from adjusting screw (7). For use during assembly, make a note of the distance from the end of the adjusting screw to upper spring seat (4). Turn the upper spring seat to release tension on pressure setting spring (5).

5. Remove the upper spring seat and pressure setting spring (5) from the adjusting screw.

6. Remove lower spring seats (6) and (8) with spring guide (9).

7. Slide piston (12) from the governor body.

8. Remove exhaust stem (10) and spring (11) from the piston. Remove inlet and exhaust valve (13) and its spring (14).

9. Remove the filter from the reservoir and unloader port.

Assemble Governor

1. Place new filters in the reservoir and unloader ports.

2. Install new O-ring seals in piston (3). Place exhaust stem (1) and spring (2) in place on the piston. Install a new inlet and exhaust valve (4) and spring (5) in the piston.

3. Put a small amount of lubricant on the piston outside diameter and in the bore of governor body (6). Slide the piston into the body.

4. Assemble adjusting screw and spring assembly (14).

a. Place lower spring seat (11), spring guide (12) and lower spring seat (9) on adjusting screw (10).

b. Install pressure setting spring (8) on the adjusting screw. Place upper spring seat (7) on the adjusting screw. Turn the seat until the dimension from the end of the adjusting screw to the seat is the same as the original dimension.

c. Install the washer and nut on the adjusting screw. Tighten the nut.

5. Install the adjusting screw and spring assembly into the governor body. Install snap ring (13).

6. Install the rubber cover on the governor.

7. Install the governor on the air compressor.

Air Compressor Testing

Install a governor assembly to the air compressor, if previously installed. Connect an oil supply line having at least 138 kPa (20 psi) of oil pressure at the rear bearing cap. Provisions must be made for unrestricted oil drainage from the crankcase during the test.

Connect a water supply line which will permit a flow of 5.7 L (1.5 gal U.S.) of water per minute at the air compressor.

Connect the discharge port to an air tank with a known volume of 5/8 inch O.D. copper line or equivalent. The tank should have a quick-opening valve to exhaust air pressure. Connect a line from the air tank to the reservoir port of the governor.

If tests are being made in a dusty atmosphere, connect a suitable air cleaner to the air compressor air inlet opening. Connect the air compressor to a source of power (at least two horsepower) to run at 1250 rpm.

Run the air compressor at 1250 rpm pumping against a 689 kPa (100 psi) pressure for five minutes. This time should be used to adjust and test the governor. During this test, check for oil and air leakage, overheating and excessive noise. Decrease the pressure in the air tank to 0 kPa (0 psi). Close the quick-opening valve and check the build-up time from 0 to 689 kPa (0 to 100 psi) in the air tank.

The build-up time must not exceed 30.0 seconds per 1000 cubic inches of tank volume for the EL-1300 Air Compressor and 24.0 seconds per 1000 cubic inches of tank volume for the EL-1600 Air Compressor.

To determine the allowable build-up time, use the following formula:

1. EL-1300 Air Compressor allowable build-up time (seconds) = air tank volume (cubic inches) × 0.030.

2. EL-1600 Air Compressor allowable build-up time (seconds) = air tank volume (cubic inches) × 0.024.

NOTE: If the air compressor is belt driven and the pulley is removed during the overhaul, it must be replaced with the same size pulley. A different size pulley will require a different size drive belt. Also, the air compressor output will change in relation to the engine rpm.

Troubleshooting

The act of troubleshooting problems for the air compressors can be difficult. The following pages contain a list of possible problems. To make a repair to a problem, make reference to the cause and correction.

This list of problems, causes, and corrections will only give an indication of where a possible problem can be, and what repairs are needed. Normally, more or other repair work is needed beyond the recommendation in the list.

Remember that a problem is not normally caused only by one part, but by the relation of one part with other parts. This list cannot give all possible problems and corrections. This service personnel must find the problems and its source, then make the necessary repairs.

1. Low Air Pressure.

2. High Air Pressure.

3. Air Pressure Decreases.

4. Not Enough Difference Between Cut-out and Cut-in Air Pressure.

5. Air Compressor With Too Much Noise.

6. Air Compressor Passes Excessive Oil.

Troubleshooting Problems

Problem 1: Low Air Pressure

Possible Causes:

1. Gauge.

2. Air Compressor Governor Adjustment.

3. Air Compressor Governor Parts.

4. Cylinder Head, Outlet Valves.

5. Cylinder Head, Inlet Valves.

6. Piston Rings. Cylinder Block, Pistons.

7. Excessive Wear to the Air Compressor.

8. Slipping of the Drive Belt.

Problem 2: High Air Pressure

Possible Causes:

1. Gauge.

2. Air Compressor Governor Adjustment.

3. Unloader Valves, Pins, or Seals.

4. Line from Supply Tank to Governor.

Problem 3: Air Pressure Decreases (no equipment in use)

Possible Causes:

1. Air Compressor Governor Parts.

2. Cylinder Head, Outlet Valves.

3. Leaks in Air System.

4. Excessive Wear to the Air Compressor.

Problem 4: Not Enough Difference Between Cut-out and Cut-in Air Pressure

Possible Causes:

1. Air Compressor Governor Parts.

2. Cylinder Head, Outlet Valves.

3. Unloader Valves.

4. Excessive Wear to the Air Compressor.

Problem 5: Air Compressor With Too Much Noise

Possible Causes:

1. Piston Rings, Cylinder Block, Pistons.

2. Crankshaft, Crankcase, Bearings.

3. Loose Drive Pulley.

4. Excessive Wear to the Air Compressor.

5. Improper Lubrication to the Air Compressor.

6. Restrictions in Cylinder Head or Discharge Line.

Problem 6: Air Compressor Passes Excessive Oil

Possible Causes:

1. Excessive Wear to the Air Compressor.

2. Dirty Air Cleaner.

3. High Inlet Vacuum (Obstructed Inlet).

4. Small or Restricted Oil Return Line is Flooding the Air Compressor.

5. Excessive Oil Pressure.

6. Defective or Worn Seal in the Rear Bearing Cap.

7. Improperly Installed Piston Rings.

8. Back Pressure from Engine Crankcase.

9. Inlet Pipe Restricted, Too Long or Too Small.

Troubleshooting Resolutions

1. Gauge

Install a test air pressure gauge, that is known to be correct, in the air system with the vehicle pressure gauge. Compare the differences in the pressures of the two gauges when the air compressor fills the air supply tank. Install a new air pressure gauge, if necessary.

2. Governor Adjustment (Midland)

Air Compressor Governor (Midland)

(1) Adjusting screw.

(2) Exhaust hole.

To increase the system air pressure, turn adjusting screw (1) in a clockwise direction. Turn the adjusting screw counterclockwise to decrease the air system pressure.

The correct cut-out pressure is 795 to 880 kPa (115 to 128 psi). The cut-in pressure is approximately 170 kPa (25 psi) less than the cut-out pressure.

3. Governor Adjustment (Bendix)

Air Compressor Governor (Bendix)

(1) Adjusting screw.

To increase the system air pressure, turn adjusting screw (1) counterclockwise. Turn the adjusting screw clockwise to decrease the air pressure.

The correct governor cut-out pressure is 795 to 860 kPa (115 to 125 psi). The cut-in setting is 660 to 690 kPa (95 to 100 psi).

4. Governor Parts

Put soap suds (water with plenty of soap) around the governor gaskets and exhaust hole (2) of the Midland governor. Bubbles must be seen from the exhaust hole only when the governor parts move to air pressure cut-in, any other bubbles show the governor needs a repair. The bubbles do not show a broken or weak spring. Refer to "Disassembly And Assembly, Air Compressor Governor".

5. Outlet Valve

The outlet valves are in the cylinder head. It is necessary to remove the cylinder head from the air compressor before the outlet valves can be removed, cleaned or replaced. Refer to "Disassembly And Assembly, Cylinder Head".

6. Inlet Valve

The inlet valves are in the cylinder head. It is necessary to remove the cylinder head from the air compressor before the inlet valves can be removed, cleaned or replaced.

7. Piston Rings. Cylinder Block, Pistons

The air compressor is removed from the engine to remove the pistons, rings and cylinder block. Refer to "Disassembly And Assembly, Pistons And Rods".

8. Unloader Valves

Air Compressor Unloader Valves

(3) Cover.

(4) Gasket.

(5) V-seal.

(6) Unloader valve.

(7) Spring.

Remove cover (3), on top of the cylinder head, over the unloader valves. Check the condition of each spring (7) and unloader valve (6). Replace, if necessary. Install new V-seals (5) and put plenty of 4L-7464 Grease-Silicone on the seals. Install the springs, the unloader valve (with a new V-seal), new gasket (4) and cover (3). Torque for the two small bolts is 9 to 12 N·m (75 to 105 lb in). Torque for the remaining long bolt is 38 to 44 N·m (27 to 33 lb ft). Refer to "Assemble Cylinder Head".

9. Line From Supply Tank

The line from the air supply tank to the inlet and filter of the air compressor governor must not have a break or a bend that would make the passage in the line too small. Install a new line, if necessary.

10. Leaks in the Air System

Check the complete air system and the air components for air leaks. When an air line connection is tightened, put soap suds (water with plenty of soap) on the connection to see if the compressed air makes bubbles in the soap suds (a leak).

11. Crankshaft, Crankcase and Bearings

The air compressor is removed from the engine to remove the crankshaft and bearings from the crankcase. Refer to "Disassembly And Assembly, Crankshaft".

Specifications

EL-1300/EL-1600 Air Compressors

Type - Two cylinder

EL-1300 Air Compressor Rating - 12.9 cubic feet per minute

EL-1600 Air Compressor Rating - 16.1 cubic feet per minute

Cylinder Head Components

Exhaust Valve Seat:

Valve guide diameter - 29.08 to 29.24 mm (1.145 to 1.151 in)

Top of valve seat to seating surface - 3.18 to 3.25 mm (.125 to .128 in)

Exhaust Valve Stop:

Valve stop surface to spring seat surface - 18.3 to 18.8 mm (.72 to .74 in)

Inlet Valve Cage:

Valve guide diameter - 23.27 to 23.37 mm (.916 to .920 in)

Top of cage to valve stop - 3.33 to 3.48 mm (.131 to .137 in)

Inlet Valve Seat:

Valve seating surface to valve cage contact surface - .597 to .673 mm (.0235 to .0265 in)

Bearing Cap

Seal diameter - 16.13 to 16.15 mm (.635 to .636 in)

(1) Cylinder head.

Unloader valve spring (two):

Length under test force - 10.2 mm (.40 in)

Test force - 15.0 to 18.6 N (3.38 to 4.18 lb)Inlet valve spring (two):

Length under test force - 7.4 mm (.29 in)

Test force - 1.6 to 2.7 N (.36 to .62 lb)Outlet valve spring (two):

Length under test force - 18.5 mm (.73 in)

Test force - 14.7 to 16.5 N (3.3 to 3.7 lb)

(2)

Torque for head bolt (six) - 37 to 44 N·m (27 to 33 lb ft)

(3)

Torque for cover head bolt - 38 to 44 N·m (28 to 33 lb ft)

(4)

Torque for cover bolt (two) - 9 to 12 N·m (75 to 105 lb in)

(5)

Torque for block bolt (six) - 23 to 26 N·m (17 to 21 lb ft)

Piston bore (new) - 69.837 to 69.850 mm (2.7495 to 2.7500 in)

(6)

Crankcase bearing bore (new) - 71.994 to 72.009 mm (2.8344 to 2.8350 in)

(7) Crankshaft.

Main bearing diameter (new) - 71.986 to 71.999 mm (2.8341 to 2.8346 in)

Rod bearing diameter (new) - 30.099 to 30.112 mm (1.1850 to 1.1855 in)

Rod bearing width (new) - 32.13 to 34.72 mm (1.265 to 1.367 in)

(8)

Torque for bolt (four) - 14 to 18 N·m (120 to 160 lb in)

(9)

Torque for bolt (six) - 13 to 17 N·m (110 to 155 lb in)

(10) Piston.

Diameter (below compression rings) - 69.677 to 69.787 mm (2.7455 to 2.7475 in)

Maximum clearance, piston to bore in block - 0.20 mm (.008 in)

Piston pin bore - 14.267 to 14.270 mm (.5615 to .5618 in)

(11)

Piston pin diameter (new) - 14.270 to 14.275 mm (.5618 to .5620 in)

(12) Compression ring end gap measured in a 69.85 mm (2.750 in) bore

Compressors built 1994 and before - 0.18 to 0.43 mm (.007 to .017 in)

Compressors built 1995 and later - 0.08 to 0.28 mm (.003 to .011 in)

Ring to groove clearance (all) - 0.013 to 0.074 mm (.0005 to .0029 in)

(13) Oil ring end gap measured in a 69.85 mm (2.750 in) bore

Compressors built 1994 and before - 0.25 to 1.02 mm (.010 to .040 in)

Compressors built 1995 and later - 0.15 to 0.66 mm (.006 to .026 in)

Ring to groove clearance (all) - 0.013 to 0.165 mm (.0005 to .0065 in)

(14) Connecting rod.

Piston pin bore - 14.280 to 14.285 mm (.5622 to .5624 in)

Clearance between rod bearing bore and crankshaft bearing diameter - 0.013 to 0.053 mm (.0005 to .0021 in)

Maximum clearance between rod bearing width and crankshaft bearing width - 0.25 mm (.010 in)

(15)

Torque for bolts - 21 to 26 N·m (185 to 225 lb in)

(16) 7N-5900 Air Compressor Governor (Midland)

Cut-out pressure setting - 895 to 985 kPa (130 to 143 psi)

Cut-in pressure setting - 725 to 815 kPa (105 to 117 psi)

7N-6577 Air Compressor Governor (Midland)

Cut-out pressure setting - 795 to 880 kPa (115 to 128 psi)

Cut-in pressure setting - 625 to 710 kpa (95 to 103 psi)

Torque for screws that hold governor to the air compressor is - 13 to 17 N·m (110 to 150 lb ft)

(17)

Torque for inlet filter - 3.4 to 6.8 N·m (30 to 60 lb in)

(18)

Torque for bolt (four) - 3.4 to 6.8 N·m (30 to 60 lb in)

(19) Pressure adjusting screw.

Turn clockwise to increase pressure setting.

(20) 4N-9680 Air Compressor Governor (Bendix)

Cut-out pressure setting - 795 to 860 kPa (115 to 125 psi)

Cut-in pressure setting - 660 to 690 kPa (95 to 100 psi)

(21) Pressure adjusting screw.

Turn counterclockwise to increase air pressure.