SD-01-344 ® Bendix® Tu-Flo® 750 Air Compressor DISCHARGE VALVE STOP UNLOADER COVER AIR DISCHARGE DISCHARGE VALVE CYLINDER HEAD WATER INLET DISCHARGE VALVE SEAT CRANKCASE PISTON RINGS CONNECTING ROD WATER OUTLET AIR INLET DISCHARGE VALVE SPRING GOVERNOR MOUNTING PAD CRANKCASE PISTON CRANKSHAFT PIECE NO.
UNLOADER COVER PLATE AIR DISCHARGE AIR DISCHARGE WATER AIR INLET WATER WATER GOVERNOR MOUNTING PAD FIGURE 1 - CYLINDER HEAD CAT MACK (MACK STYLE) MACK EXTENDED MACK "FOXHEAD" CUMMINS DETROIT DIESEL FIGURE 2 - MOUNTING CONFIGURATIONS Various mounting and drive configurations, as shown in Figure 2, are supplied as required by the vehicle engine designs. A nameplate identifying the compressor piece number and serial number is attached to the side of the crankcase. (Reference Figure 3.
AIR DISCHARGE PORT DISCHARGE PORT GOVERNOR PORT UNLOADER PISTON GOVERNOR PORT AIR INLET PORT AIR INLET PORT DISCHARGE VALVE CLOSED INLET VALVE OPEN DISCHARGE VALVE CLOSED INLET VALVE HELD OPEN BY UNLOADER PISTON PISTON MOVING DOWN FIGURE 4 - OPERATIONAL-LOADED (INTAKE) AIR DISCHARGE PORT FIGURE 6 - OPERATIONAL-UNLOADED GOVERNOR PORT governor closes and exhausts the air from above the unloader pistons. The unloader springs force the pistons upward and the inlet valves return to their seats.
The Air Brake Charging System supplies the Discharge Line Optional “Ping” Tank Air Dryer compressed air for the braking system as well as other air accessories for the vehicle. The system usually consists of an air compressor, governor, discharge line, air dryer, and service reservoir.
DISCHARGE LINE TEMPERATURE COOLING When the temperature of the compressed air that enters the air dryer is within the normal range, the air dryer can remove most of the charging system oil. If the temperature of the compressed air is above the normal range, oil as oil-vapor is able to pass through the air dryer and into the air system. Larger diameter discharge lines and/or longer discharge line lengths can help reduce the temperature.
If a previously unturbocharged compressor is being turbocharged, it is recommended that the inlet cavity screen (238948) be installed with an inlet gasket (291909) on both sides of the screen. AIR INDUCTION COMPRESSOR TURBOCHARGING PARAMETERS One of the single most important aspects of compressor preventive maintenance is the induction of clean air. The type and interval of maintenance required will vary depending upon the air induction system used.
DRY ELEMENT - PLEATED PAPER STRAINER OIL PASSING Every two months, 800 operating hours or 20,000 miles whichever occurs first, loosen the spring clip from the unhinged side of the mounting baffle and open the cover. Replace the pleated paper filter and secure the cleaned cover, making sure the filter is in position. Be sure to replace the air strainer gasket if the entire air strainer is removed from the compressor intake.
AIR LEAKAGE TESTS Compressor leakage tests need not be performed on a regular basis. These tests should be performed when; it is suspected that discharge valve leakage is substantially affecting compressor build-up performance, or when it is suspected that the compressor is “cycling” between the load and unloaded modes due to unloader piston leakage. These tests must be performed with the vehicle parked on a level surface, the engine not running, the entire air system completely drained to 0 P.S.I.
4. Remove the inlet valve stops (14), valves (17), valve seats (11), valve springs (12) and gaskets (10). It is recommended that a tool such as a J-25447-B, produced by Kent Moore Tool Division Roseville, Michigan phone 1-800-328-6657, be used to remove the inlet valve stop. CLEANING OF PARTS GENERAL All parts should be cleaned in a good commercial grade of solvent and dried prior to inspection. CYLINDER HEAD 1. Remove the cap screws (22) securing the bottom cover or adapter (21).
2 3 1 23 4 23 5 24 6 7 CYLINDER HEAD 25 24 8 26 9 15 27 28 23 24 16 17 18 25 10 11 12 13 14 19 41 24 37 33 32 36 31 CRANKCASE 35 30 34 29 32 31 38 NAMEPLATE 39 32 BALL BEARING (MACK EXTENDED FLANGE) 20 40 21 22 FIGURE 11 - EXPLODED VIEW ITEM 1 2 3 4 5 6 7 8 9 10 11 12 13 14 10 QTY 6 4 4 1 1 2 2 2 2 2 2 2 2 2 DESCRIPTION Cylinder Head Cap Screws Unloader Plate Cap Screws Unloader Plate Lock Washers Unloader Plate Unloader Plate Gasket O-ring Unloader Spring Unloader Bushing G
in. should be rebored or honed oversize. Oversized pistons and piston rings are available in .010 in., .020 in. and .030 in. oversizes. Cylinder bores must be smooth, straight and round. Clearance between the cast iron pistons and cylinder bores should be between .002 in. minimum and .004 in. maximum. PISTON RINGS Check the pistons for scores, cracks or enlarged ring grooves; replace the pistons if any of these conditions are found.
INLET VALVES AND SEATS PISTON RINGS Inlet valves and springs should be replaced. However, if the inlet valve seats show signs of slight nicks or scratches, they can be redressed with a fine piece of emery cloth or by lapping with a lapping stone, grinding compound and grinding tool. If the seats are damaged to the extent that they cannot be reclaimed, they must be replaced. Check each ring end gap in a cylinder bore before installation.
2. Install the compression rings (23) in the proper grooves with the “pip” mark toward the top of the piston. (Refer to Figure 14.) Check the ring side clearance of each ring in the piston ring groove. (Refer to Figure 12.) If the side clearance is too large, the piston ring groove is worn beyond specifications and the piston must be replaced. Rotate the piston rings in their respective groove so that each end gap is at least 90 degrees from the previous ring’s end gap.
Minimum oil pressure required at engine idling speed ............................................ 15 PSIG Minimum oil pressure required at maximum governed engine speed .................... 15 PSIG Minimum discharge-line size ............................. 1/2" I.D. Minimum coolant-line size ................................. 3/8" I.D. Minimum oil-supply line size ............................ 3/16" I.D. Minimum oil-return line size ............................... 1/2" I.D. Minimum air-inlet line size ........
7. Never connect or disconnect a hose or line containing pressure; it may whip. Never remove a component or plug unless you are certain all system pressure has been depleted. 8. Use only genuine Bendix® replacement parts, components and kits. Replacement hardware, tubing, hose, fittings, etc. must be of equivalent size, type and strength as original equipment and be designed specifically for such applications and systems. 9.
This troubleshooting guide obsoletes and supersedes all previous published troubleshooting information relative to Bendix air compressors. Advanced Troubleshooting Guide for Air Brake Compressors * The guide consists of an introduction to air brake charging system components, a table showing recommended vehicle maintenance schedules, and a troubleshooting symptom and remedy section with tests to diagnose most charging system problems.
Introduction to the Air Brake Charging System Powered by the vehicle engine, the air compressor builds the air pressure for the air brake system. The air compressor is typically cooled by the engine coolant system and lubricated by the engine oil supply.
Table A: Maintenance Schedule and Usage Guidelines Regularly scheduled maintenance is the single most important factor in maintaining the air brake charging system. Column 1 Vehicle Used for: Typical Compressors No. of Spec'd Axles Column 2 Discharge Line I.D. Length 1/2 in. 6 ft. Column 3 Recommended Air Dryer Cartridge Replacement1 Column 4 Recommended Reservoir Drain Schedule2 Column 5 Acceptable Reservoir Oil Contents3 at Regular Drain Interval e.g.
Air Brake Charging System Troubleshooting How to use this guide: Find the symptom(s) that you see, then move to the right to find the possible causes (“What it may indicate”) and remedies (“What you should do”). Review the warranty policy before performing any intrusive compressor maintenance. Unloader or cylinder head gasket replacement and resealing of the bottom cover plate are usually permitted under warranty. Follow all standard safety procedures when performing any maintenance.
Symptom: What it may indicate: What you should do: 2.0 Oil on the Outside of the Compressor Engine and/or other accessories leaking onto compressor. Find the source and repair. Return the vehicle to service. 2.1 Oil leaking at compressor / engine connections: (a)Leak at the front or rear (fuel pump, etc.) mounting flange. Repair or replace as necessary. If the mounting bolt torques are low, replace the gasket. (b)Leak at air inlet fitting. Replace the fitting gasket.
Symptom: What it may indicate: 4.0 Oil in Supply or Service Reservoir (air dryer installed) ® (If a maintained Bendix PuraGuard® system filter or Bendix® PuraGuard® QC™ oil coalescing filter is installed, call 1-800-AIR-BRAKE (1-800-247-2725) and speak to a Tech Team member.) What you should do: Maintenance (a) If air brake charging system maintenance has not been performed.
Symptom: 4.0 Oil in Supply or Service Reservoir* (air dryer installed) (continued) What it may indicate: What you should do: Temperature (e) Air compressor discharge and/or air dryer inlet temperature too high. Check temperature as outlined in Test 3 on page 29. If temperatures are normal go to 4.0(h). (f) Insufficient coolant flow. Inspect coolant line. Replace as necessary (I.D. is 1/2"). Inspect the coolant lines for kinks and restrictions and fittings for restrictions. Replace as necessary.
Symptom: 4.0 Oil in Supply or Service Reservoir* (air dryer installed) (continued) What it may indicate: What you should do: Other (cont.) (i) Poorly filtered inlet air (poor air quality to compressor). Check for leaking, damaged or defective compressor air inlet components (e.g. induction line, fittings, gaskets, filter bodies, etc.). Repair inlet components as needed. Note: Dirt ingestion will damage compressor and is not covered under warranty. Inspect the engine air cleaner.
Symptom: What it may indicate: 6.0 Excessive oil consumption in engine. A problem with engine or other engine accessory. 7.0 Oil present at air dryer cartridge during maintenance. Air brake charging system is functioning normally. See engine service manual. The engine service manual has more information. Oil shown leaking from an air dryer cartridge. 24 What you should do: Air dryers remove water and oil from the air brake charging system. A small amount of oil is normal.
Symptom: 9.0 Air brake charging system seems slow to build pressure. (continued) What it may indicate: (f) Restricted discharge line. (f) Dash gauges. Kinked discharge line shown. (g) Restricted air inlet (not enough air to compressor). (g) What you should do: If discharge line is restricted: By more than 1/16" carbon build up, replace the discharge line (see Table A, column 2, on page 18 for recommended size) and go to Test 3 on page 29. By other restrictions (e.g. kinks). Replace the discharge line.
Symptom: 10.0 Air charging system doesn’t build air. What it may indicate: (a) Governor malfunction*. Go to Test 4 on page 30. (b) Restricted discharge line. See 9.0(f). (c) Air dryer heater malfunction: exhaust port frozen open. Replace air dryer heater. (d) Compressor malfunction. Replace the compressor only after making certain the preceding conditions do not exist.
Symptom: 12.0 Air dryer safety valve releases air. What it may indicate: (a) Restriction between air dryer and reservoir. Inspect delivery lines to reservoir for restrictions and repair as needed. (b) Air dryer safety valve malfunction. Verify relief pressure is at vehicle or component manufacturer specifications. Replace if defective. (c) A i r d r y e r m a i n t e n a n c e n o t performed. See Maintenance Schedule and Usage Guidelines (Table A, column 3, on page 18). (d) Air dryer malfunction.
Symptom: 16.0 Compressor leaks air Testing for leaks with soap solution. 17.0 Compressor leaks coolant 18.0 Noisy compressor (Multi-cylinder compressors only) What it may indicate: What you should do: (a) C o m p r e s s o r l e a k s a i r a t connections or ports. Check for leaking, damaged or defective compressor fittings, gaskets, etc. Repair or replace as necessary. (b) Compressor unloader mechanism malfunction. Go to Test 6 on page 30. (c) D a m a g e d c o m p r e s s o r h e a d gasket.
Tests Test 1: Excessive Oil Leakage at the Head Gasket Exterior leaks at the head gasket are not a sign that oil is being passed into the air charging system. Oil weepage at the head gasket does not prevent the compressor from building air. Observe the amount of weepage from the head gasket. If the oil is only around the cylinder head area, it is acceptable (return the vehicle to service), but, if the oil weepage extends down to the nameplate area of the compressor, the gasket can be replaced.
Tests (continued) Test 4: Governor Malfunction 1. Inspect control lines to and from the governor for restrictions (e.g. collapsed or kinked). Repair as necessary. 2. Using a calibrated external gauge in the supply reservoir, service reservoir, or reservoir port of the D-2® governor, verify cut-in and cut-out pressures are within vehicle OEM specification. 3. If the governor is malfunctioning, replace it. Test 5: Governor Control Line 1.
NOTES 31
Appendix A: Information about the BASIC Test Kit (Bendix P/N 5013711) Service writer records info - including the number of days since all air tanks were drained - and fills out symptom checklist. Technician inspects items. days Bendix® Air System Inspection Cup (BASIC) Test Information START BASIC TEST Park vehicle on LEVEL ground. Chock wheels, drain air from system. Drain contents of ALL air tanks into BASIC™ cup Is there less than one unit of liquid? Vehicle OK. Return vehicle to service.
Appendix A continued: Information about the BASIC Test Kit (Bendix P/N 5013711) ® Filling in the Checklist for the Bendix Air System Inspection Cup (BASIC) Test Note: Follow all standard safety precautions. For vehicles using a desiccant air dryer.
Appendix A continued: Information about the BASIC Test Kit (Bendix P/N 5013711) ® Filling in the Checklist for the Bendix Air System Inspection Cup (BASIC) Test Note: Follow all standard safety precautions. For vehicles using a desiccant air dryer. STEP C - How to Use the BASIC Test 1. Record days since air tanks were last drained. 2. Record amount of oil found: The Technician uses the chart (label) on the BASIC test cup to help decide the action to take, based on the amount of oil found.
Appendix B Technical Bulletin Bulletin No.: TCH-008-021 Subject: Air Effective Date: 11/1/92 Page: 1 of 2 Brake System - Cold Weather Operation Tips As the cold weather approaches, operators and fleets alike begin to look to their vehicles with an eye toward “winterization”, and particularly what can be done to guard against air system freeze-up. Here are some basic “Tips” for operation in the cold weather.
Appendix B: Continued Bulletin No.: TCH-008-021 Effective Date: 11/1/92 Page: 2 of 2 High Duty Cycle Vehicles (City Transit Coaches, Refuse Haulers, Etc.) The maximum discharge line length is 16 feet. Length I.D. min. Other Requirements 10-16 ft. ½ in. None If the discharge line length must be less than 10 feet or greater than 16 feet, contact your local Bendix representative.
Appendix B: Continued Technical Bulletin Bulletin No.: TCH-008-022 Subject: Additional Effective Date: 1/1/1994 Page: 1 of 1 Cold Weather Operation Tips for the Air Brake System Last year we published Bulletin PRO-08-21 which provided some guidelines for “winterizing” a vehicle air brake system. Here are some additional suggestions for making cold weather vehicle operation just a little more bearable.
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