Advanced Troubleshooting Guide For Air Brake Compressors

Air Brake Charging System TroubleshootingHow to use this guide:Find the symptom(s) that you see, then move to the right tofind the possible causes (“What it may indicate”) andremedies (“What you should do”).Review the warranty policy before performing any intrusivecompressor maintenance. Unloader or cylinder head gasketreplacement and resealing of the bottom cover plate areusually permitted under warranty. Follow all standard safetyprocedures when performing any maintenance.WARNING! Please READ and follow these instructions toavoid personal injury or death:When working on or around a vehicle, the following generalprecautions should be observed at all times.1. Park the vehicle on a level surface, apply the parkingbrakes, and always block the wheels. Always wear safetyglasses.2. Stop the engine and remove ignition key when workingunder or around the vehicle. When working in the enginecompartment, the engine should be shut off and the ignitionkey should be removed. Where circumstances require thatthe engine be in operation, EXTREME CAUTION shouldbe used to prevent personal injury resulting from contactwith moving, rotating, leaking, heated or electrically chargedcomponents.3. Do not attempt to install, remove, disassemble or assemblea component until you have read and thoroughlyunderstand the recommended procedures. Use only theproper tools and observe all precautions pertaining to useof those tools.4. If the work is being performed on the vehicle’s air brakesystem, or any auxiliary pressurized air systems, makecertain to drain the air pressure from all reservoirs beforebeginning ANY work on the vehicle. If the vehicle isequipped with an AD-IS air dryer system or a dryerreservoir module, be sure to drain the purge reservoir.Symptom:1.0 Oil Test CardResultsLook for:Normal - Charging system is working withinnormal range.Check - Charging system needs furtherinvestigation.5. Following the vehicle manufacturer’s recommendedprocedures, deactivate the electrical system in a mannerthat safely removes all electrical power from the vehicle.6. Never exceed manufacturer’s recommended pressures.7. Never connect or disconnect a hose or line containingpressure; it may whip. Never remove a component or plugunless you are certain all system pressure has beendepleted.8. Use only genuine Bendix replacement parts, componentsand kits. Replacement hardware, tubing, hose, fittings, etc.must be of equivalent size, type and strength as originalequipment and be designed specifically for suchapplications and systems.9. Components with stripped threads or damaged partsshould be replaced rather than repaired. Do not attemptrepairs requiring machining or welding unless specificallystated and approved by the vehicle and componentmanufacturer.10. Prior to returning the vehicle to service, make certain allcomponents and systems are restored to their properoperating condition.11. For vehicles with Antilock Traction Control (ATC), the ATCfunction must be disabled (ATC indicator lamp should beON) prior to performing any vehicle maintenance whereone or more wheels on a drive axle are lifted off the groundand moving.What it may indicate:What you should do:Not a valid test.Discontinue using this test.Do not use this card test to diagnosecompressor "oil passing" issues. They aresubjective and error prone. Use only theBendix Air System Inspection Cup (BASIC) testand the methods described in this guide foradvanced troubleshooting.The Bendix BASIC test should be thedefinitive method for judging excessive oilfouling/oil passing. (See Appendix A, onpage 17 for a flowchart and expandedexplanation of the checklist used whenconducting the BASIC test.)ûBendix BASIC Testü4

Symptom:What it may indicate:What you should do:2.0 Oil on theOutside of theCompressorEngine and/or other accessoriesleaking onto compressor.Find the source and repair. Return the vehicleto service.2.1 Oil leaking atcompressor / engineconnections:(a)Leak at the front or rear (fuelpump, etc.) mounting flange.ð Repair or replace as necessary. If themounting bolt torques are low, replace thegasket.(b)Leak at air inlet fitting.ð Replace the fitting gasket. Inspect inlethose and replace as necessary.(c)Leak at air discharge fitting.ð Replace gasket or fitting as necessary toensure good seal.(d)Loose/broken oil line fittings.ð Inspect and repair as necessary.(a)Excessive leak at head gasket.ð Go to Test 1 on page 14.(b)Leak at bottom cover plate.ð Reseal bottom cover plate using RTVsilicone sealant.(c)Leak at internal rear flange gasket.ð Replace compressor.(d)Leak through crankcase.ð Replace compressor.(e)(If unable to tell source of leak.)ð Clean compressor and check periodically.2.2 Oil leakingfrom compressor:ð(c)(a)ð(c)3.0 Oil at air dryerpurge/exhaust orsurrounding areaHeadgasketand rearflangegasketlocations.Air brake charging system functioningnormally.5ð Air dryers remove water and oil from theair brake charging system.Check that regular maintenance is beingperformed. Return the vehicle to service.An optional kit (Bendix piece number5011327 for the Bendix AD-IS or AD-IP air dryers, or 5003838 for the Bendix AD-9 air dryer) is available to redirect theair dryer exhaust.

Symptom:What it may indicate:4.0 Oil in Supply orService Reservoir(air dryer installed)(If a maintained BendixPuraGuard systemfilter or Bendix PuraGuard QC oilcoalescing filter isinstalled, call1-800-AIR-BRAKE(1-800-247-2725) andspeak to a Tech Teammember.) What you should do:Maintenance(a) If air brake charging systemmaintenance has not beenperformed.That is, reservoir(s) have not beendrained per the schedule in TableA on page 3, Column 4 and/or theair dryer maintenance has notbeen performed as in Column 3.ð Drain all air tanks and check vehicle at nextservice interval using the Bendix BASICtest. See Table A on page 3, column 3and 4, for recommended service schedule.(b) If the vehicle maintenance hasbeen performed as recommended in Table A on page 3,some oil in the reservoirs is normal.ð Drain all air tanks into Bendix BASIC testcup (Bendix Air System Inspection Cup).If less than one unit of reservoir contentsis found, the vehicle can be returned toservice. Note: If more than one oil unitof water (or a cloudy emulsion mixture)is present, change the vehicle's airdryer, check for air system leakage (Test2, on page 14), stop inspection andcheck again at the next service interval.See the BASIC test kit for full details.If less than one "oil unit" of water (or water/cloudy emulsion mixture) is present, usethe BASIC cup chart on the label of thecup to determine if the amount of oil foundis within the acceptable level.ðIf within the normal range, return thevehicle to service. For vehicles withaccessories that are sensitive to smallamounts of oil, consider a Bendix PuraGuard QC oil coalescing filter.ð If outside the normal range go toSymptom 4.0(c).Also see the Table A on page 3, column 3for recommended air dryer cartridgereplacement schedule.(a)See Table A, on page 3,for maintenanceschedule information.Drain all air tanks (reservoirs)into the Bendix BASIC testcup. (Bendix kit P/N 5013711).Duty cycle too high(c) Air brake system leakage.ð Go to Test 2 on page 14.(d) Compressor may be undersized forthe application.ð See Table A, column 1, on page 3 forrecommended compressor sizes.ð If the compressor is "too small" forthe vehicle's role (for example, where avehicle's use has changed or serviceconditions exceed the original vehicle orengine OE spec's) then upgrade thecompressor. Note: The costs incurred (e.g.installing a larger capacity compressor,etc.) are not covered under originalcompressor warranty.ð If the compressor is correct for thevehicle, go to Symptom 4.0 (e).The duty cycle is the ratio of time the compressor spendsbuilding air to total engine running time. Air compressorsare designed to build air (to "run loaded") up to 25% of thetime. Higher duty cycles cause conditions that affect airbrake charging system performance which may requireadditional maintenance. Factors that add to the duty cycleare: air suspension, additional air accessories, use of anundersized compressor, frequent stops, excessive leakagefrom fittings, connections, lines, chambers or valves, etc.6

Symptom:What it may indicate:4.0 Oil in Supplyor ServiceReservoir*(air dryer installed)(continued)What you should do:Temperature(e) Air compressor discharge and/orair dryer inlet temperature too high.ð Check temperature as outlined in Test 3on page 14. If temperatures are normalgo to 4.0(h).(f) Insufficient coolant flow.ð Inspect coolant line. Replace as necessary(I.D. is 1/2").ð Inspect the coolant lines for kinks andrestrictions and fittings for restrictions.Replace as necessary.(f)(e)ð Verify coolant lines go from engine blockto compressor and back to the water pump.Repair as necessary.(g)Testing the temperatureat the discharge fitting.Inspecting the coolant hoses.(g) Restricted discharge line.(g)ð If discharge line is restricted or more than1/16" carbon build up is found, replace thedischarge line. See Table A, column 2, onpage 3 for recommended size. Replace asnecessary.ð The discharge line must maintain aconstant slope down from the compressorto the air dryer inlet fitting to avoid lowpoints where ice may form and block theflow. If, instead, ice blockages occur at theair dryer inlet, insulation may be addedhere, or if the inlet fitting is a typical 90degree fitting, it may be changed to astraight or 45 degree fitting. For moreinformation on how to help prevent dischargeline freeze-ups, see Bendix BulletinsTCH-08-21 and TCH-08-22 (Appendix B).Shorter discharge line lengths or insulationmay be required in cold climates.Kinked discharge line shown.Other(h) Restricted air inlet (not enough airto compressor).(h)ð Check compressor air inlet line forrestrictions, brittleness, soft or sagginghose conditions etc. Repair as necessary.Inlet line size is 3/4 ID. Maximumrestriction requirement for compressors is25 inches of water.ð Check the engine air filter and service ifnecessary (if possible, check the air filterusage indicator).Partlycollapsedinlet lineshown.*If a maintained Bendix PuraGuard system filter or Bendix PuraGuard QC oil coalescingfilter is installed, call 1-800-AIR-BRAKE (1-800-247-2725) and speak to a Tech Teammember.7

Symptom:4.0 Oil in Supplyor ServiceReservoir*(air dryer installed)(continued)What it may indicate:What you should do:Other (cont.)(i) Poorly filtered inlet air (poor airquality to compressor).Inspect theengine aircleaner.ð Check for leaking, damaged or defectivecompressor air inlet components (e.g.induction line, fittings, gaskets, filter bodies,etc.). Repair inlet components as needed.Note: Dirt ingestion will damagecompressor and is not covered underwarranty.(j) Governor malfunction or setting.ð Go to Test 4 on page 15.(k) Compressor malfunction.ð If you found excessive oil present in theservice reservoir in step 4.0 (b) above andyou did not find any issues in steps 4.0 (c)through 4.0 (j) above, the compressor maybe passing oil.Replace

air dryer, and service reservoir. 3 Compressor with up to 25% duty cycle Footnotes: 1 With increased air demand the air dryer cartridge needs to be replaced more often. 2 Use the drain valves to slowly drain all reservoirs to zero psi. 3 Allow the oil/water mixture to fully settle before measuring oil quantity.