SD-01-690 BENDIX® BA-921® COMPRESSOR: STANDARD AND CLOSED ROOM "STANDARD" AND "CLOSED ROOM" VERSIONS This service data sheet covers two versions of the Bendix® BA-921® compressor. The first version was originally released in 2002 and will be referred to as the “Standard” compressor in this Service Data sheet. The Standard compressor was offered on Caterpillar ACERT Medium and Heavy duty engines, and the DDC S60 EGR (2002-06) engine.
Splash Shield Coolant Ports (3 total) Unloader Cover Unloader Piston Unloader Cover Coolant Ports (3 total) Unloader Piston Air Intake Cooling Plate Discharge Reed Valves (2) Cooling Plate Discharge Reed Valves (2) Crankshaft Piston Piston Piston Rod Piston Rod Crankshaft Crankcase Cover Standard Closed Room Crankcase Cover FIGURE 3 - BENDIX® BA-921® COMPRESSOR (CUT-AWAY) (STANDARD AND CLOSED ROOM) The compressor's discharge valves are part of the valve plate assembly.
Standard Compressors use an Inlet Check Valve (ICV), or alternately, an ICV plus a reservoir, in the air inlet line depending on the application Air Discharge Port Air Inlet Port Discharge Valve Closed Unloader Port Air Dryer Governor Unloader Port Cooling Plate Governor Reservoir Port Valve Plate Unloader Piston Down & Seated Compressor Supply Reservoir Inlet Valve Open Closed Room Compressor Typical System Governor Unloader Port Air Dryer Piston Moving Down FIGURE 7A - OPERATION - LOADED (INT
Air Inlet Port Cooling Plate Valve Plate Air From Governor Unloader Port Air From Governor Unloader Port Unloader Piston Up & Unseated Closed Room Unloader Piston Up & Unseated Air in Pistons Shuttles Back and Forth from the Piston to the Cylinder Head and Inlet Port During Unloaded Mode FIGURE 8 - OPERATION - UNLOADED (STANDARD) Air in Pistons Shuttles Back and Forth from the Piston to the Closed Room FIGURE 9 - OPERATION - UNLOADED (CLOSED ROOM) NON-COMPRESSION OF AIR (UNLOADED) Section 1: For Sta
LUBRICATION Head Bolt (4) Discharge Safety Valve Coolant In or Out (One or other not used) Discharge Port Governor Connection Inlet Port Unloader Cover Standard Compressor Lubrication for Caterpillar C11 and C13 engine applications Coolant In or Out CYLINDER HEAD PORT IDENTIFICATION The cylinder head connection ports are identified with cast in numerals as follows: AIR IN 0 Compressed AIR OUT 2 Coolant IN or OUT 9 Governor Control 4 FIGURE 10 - STANDARD BENDIX® BA-921® COMPRESSOR CYLINDER HEAD Head
CATERPILLAR Inlet Port Inlet Line Inlet Check Valve Air Supply From Engine FIGURE 12 - EXAMPLE OF CATERPILLAR (ACERT ENGINE) C7/C9 COMPRESSOR AIR INDUCTION SYSTEM (TURBOCHARGED) Inlet Line Expansion Tank Inlet Port Air Supply From Engine Caterpillar HD ACERT engines (C11, C13, C15 and C18) and MD ACERT engines (C7 and C9) are typically equipped with Bendix ® BA-921 ® compressors. These engines provide pressurized (turbocharged) air to the compressor's inlet port.
CATERPILLAR C11, C13, C15 AND C18 ENGINES ® ® The Bendix BA-921 compressor in the C11, C13, C15, and C18 air induction systems (see Figure 13) receives its air from the engine's intake manifold (turbocharged). During the pumping condition (loaded mode), the air flows from the engine intake manifold through the inlet check valve, expansion tank and inlet line to the compressor inlet port.
buildup indicates inadequate cooling. Closely inspect the compressor cooling system. Check all compressor coolant lines for kinks and restrictions to flow. Minimum coolant line size is 3/8" I.D. Check coolant lines for internal clogging from rust scale. If coolant lines appear suspicious, check the coolant flow and compare to the tabulated technical data present in the back of this manual. Carefully inspect the air induction system for restrictions. LUBRICATION Caterpillar Engine Installations.
1 Head Cap Screws (4) (include washers) See Figure 10 for Port Details.
1 Head Cap Screws (6) (include washers) 12 ST-4™ Safety Valve 2 Unloader Cover Cap Screws (2) 4 Unloader Cover 5 Unloader Cover Gasket 6 Unloader Balance Piston See Figure 11 for Port Details.
IN SERVICE OPERATING TESTS CYLINDER HEAD Compressor Performance: Build-up Test Check for cylinder head gasket air leakage. This test is performed with the vehicle parked and the engine operating at maximum recommended governed speed. Fully charge the air system to governor cut out (air dryer purges). Pump the service brake pedal to lower the system air pressure below 80 psi using the dash gauges.
2. The compressor should remain unloaded for a minimum of 5-10 minutes. If compressor cycling occurs more frequently and service and supply system leakage is within tolerance replace the compressor or repair the compressor unloader system using a genuine Bendix maintenance kit available from authorized Bendix parts outlets.
unless specifically stated and approved by the vehicle and component manufacturer. 10. Prior to returning the vehicle to service, make certain all components and systems are restored to their proper operating condition. 11. For vehicles with Antilock Traction Control (ATC), the ATC function must be disabled (ATC indicator lamp should be ON) prior to performing any vehicle maintenance where one or more wheels on a drive axle are lifted off the ground and moving.
Section 2: Closed Room Compressor (refer to Figure 16) Side View 1. Remove the discharge safety valve (12) from the cylinder head (13). 2. To restrain the spring force exerted by balance piston spring (8) of the unloader assembly, hold the unloader cover (4) in place while removing the two unloader cover cap screws (2). Carefully release the hold on the unloader cover until the spring force is relaxed, then remove the unloader cover. 3. Remove the unloader cover gasket (5). 4.
plate assembly. They must be open and clear in both assemblies. Make certain not to damage the head. 3. Remove rust and scale from the cooling cavities and passages in the cylinder head, cooling plate and valve plate assembly and use shop air to clear debris from the passages. 4. Check the threads in all cylinder head ports for galling (e.g. abrasion, chafing). Minor thread chasing (damage) is permitted. 5.
a. Position the gasket (27) on either the crankcase or the special crankcase cover and install the special crankcase cover on the crankcase using the four cap screws. Note: Make sure that the cover is orientated in its original position. “Snug” all four cap screws then torque to 62-71 inch pounds (7-8 N•m) using a crossing pattern. b.
4. Install the cooling plate onto valve plate assembly by lining up the alignment bushings on the cooling plate over the oversized countersunk holes of the valve plate assembly. Again, when properly installed, the outline of the cooling plate matches the outline of the valve plate. engine installations, an additional o-ring is required to seal the oil feed passageway between the compressor and engine gear case cover. Gasket sealants are not recommended.
BA-921® COMPRESSOR SPECIFICATIONS (ALL) TORQUE SPECIFICATIONS: Standard Typical weight: Compressor Standard Compressor (DDC Model) ............................... 66 lbs. Closed Room Compressor (DDC Model) ........................ 55 lbs. Number of cylinders ......................................................................... 1 Bore Diameter ....................................................... 3.622 in. (92 mm) Stroke ................................................................... 2.126 in.
Appendix A 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. INDEX Symptom Page Number Air Symptom Page Number Coolant Air brake charging system: Slow build (9.0) .....................................A-9-10 Doesn’t build air (10.0) .........................
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 Vehicle Used for: No. of Axles Column 1 Column 2 Typical Compressors Spec'd Discharge Line (See footnote 7) 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 Look for: 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 A-14. If temperatures are normal go to 4.0(h). Inspect coolant line. Replace as necessary (I.D. is 1/2"). (f) Insufficient coolant flow. 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. What you should do: See engine service manual. The engine service manual has more information. Oil shown leaking from an air dryer cartridge. 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. Engine Oil Quality Inadequate oil change intervals, the formulation of the oil and/or the quality of oil filter used can all lead to poor oil quality. These can increase the rate at which carbon builds up in the discharge line. Bendix recommends oil soot (solids) be maintained at less than 3%.
Symptom: 10.0 Air charging system doesn’t build air. What it may indicate: (a) Governor malfunction*. Go to Test 4 on page A-15. (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. Air dryer safety valve Technician removes governor. 13.0 Reservoir safety valve releases air 14.0 Air dryer doesn’t purge. (Never hear exhaust from air dryer.) 15.0 Compressor constantly cycles (compressor remains unloaded for a very short time.) A-12 What it may indicate: What you should do: (a) Restriction between air dryer and reservoir. Inspect delivery lines to reservoir for restrictions and repair as needed.
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) Compressor leaks air at 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 A-15. (c) Damaged compressor head gasket(s).
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. Look for Weepage Observe the amount of weepage from the head gasket.
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.
Appendix B: 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 B 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 B 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 C Technical Bulletin Bulletin No.: TCH-008-021 Page: 1 of 2 Subject: Air Effective Date: 11/1/92 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 C: Continued Bulletin No.: TCH-008-021 Page: 2 of 2 Effective Date: 11/1/92 High Duty Cycle Vehicles (City Transit Coaches, Refuse Haulers, Etc.) The maximum discharge line length is 16 feet. Length 10-16 ft. ½ in. I.D. min. Other Requirements None If the discharge line length must be less than 10 feet or greater than 16 feet, contact your local Bendix representative.
Appendix D Technical Bulletin Bulletin No.: TCH-008-022 Page: 1 of 1 Subject: Additional Effective Date: 1/1/1994 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.
BW2369 © 2007 Bendix Commercial Vehicle Systems LLC. All Rights Reserved. 10/07. Printed in U.S.A.
