Bendix Commercial Vehicle Systems TROUBLE SHOOTING COMPRESSOR User Manual

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.

Symptom Page Number

Air

Air brake charging system:

Slow build (9.0) ...................9 - 10

Doesn’t build air (10.0) .................11

Air Dryer:

Doesn’t purge (14.0) ..................12

Safety valve releases air (12.0) ..........12

Compressor:

Constantly cycles (15.0) ...............13

Leaks air (16.0) ......................13

Safety valve releases air (11.0) ..........11

Noisy (18.0) ........................13

Reservoir:

Safety valve releases air (13.0) ..........12

INDEX

Symptom Page Number

Coolant

Compressor leaks coolant (17.0). . . . . . . . . . . . 13

Engine

Oil consumption (6.0) .....................9

Oil

Oil Test Card results (1.0) ..................4

Oil is present:

On the outside of the compressor (2.0) .....5

At the air dryer purge/exhaust

or surrounding area (3.0) ..............5

In the supply reservoir (4.0) ........... 6 - 8

At the valves (5.0) .....................8

At air dryer cartridge (7.0) ...............9

In the ping tank or compressor

discharge aftercooler (8.0) .............9

Test Procedures

(1) Oil Leakage at Head Gasket ............14

(2) System Leakage .....................14

(3) Compressor Discharge and

Air Dryer Inlet Temperature ............14

(4) Governor Malfunction .................14

(5) Governor Control Line .................15

(6) Compressor Unloader .................15

BASIC Test Information ................ 17-19

Maintenance & Usage Guidelines

Maintenance Schedule and Usage Guidelines

(Table A) .................... 3

Note: The technical bulletins referenced in this

document are available at www.Bendix.com.

*This guide is only for vehicles that use desiccant air dryers.

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.

The compressor's unloader mechanism and governor (along with a synchro valve for the Bendix® DuraFlo 596

™

air compressor) control the brake system air pressure between a preset maximum and minimum pressure level by monitoring the pressure in the service (or “supply”) reservoir. When the air pressure becomes greater than that of the preset “cut-out”, the governor controls the unloader mechanism of the compressor to stop the compressor from building air and also causes the air dryer to purge. As the service reservoir air pressure drops to the “cut-in” setting of the governor, the governor returns the compressor back to building air and the air dryer to air drying mode.

As the atmospheric air is compressed, all the water vapor originally in the air is carried along into the air system, as well as a small amount of the lubricating oil as vapor.

The duty cycle is the ratio of time the compressor spends building air to the total engine running time. Air compressors are designed to build air (run “loaded”) up to 25% of the time. Higher duty cycles cause conditions that affect air brake charging system performance which may require additional maintenance. Factors that add to the duty cycle are: air suspension, additional air accessories, use of an undersized compressor, frequent

stops, excessive leakage from ttings, connections,

lines, chambers or valves, etc. The discharge line allows the air, water-vapor and

oil-vapor mixture to cool between the compressor and air dryer. The typical size of a vehicle's discharge line, (see column 2 of Table A on page 3) assumes

a compressor with a normal (≤ 25%) duty cycle and

operating in a temperate climate. See Bendix and/ or other air dryer manufacturer guidelines as needed.

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.

The discharge line must maintain a constant slope

down from the compressor to the air dryer inlet tting to avoid low points where ice may form and block the ow.

If, instead, ice blockages occur at the air dryer inlet,

insulation may be added here, or if the inlet tting is a typical 90 degree tting, it may be changed to a straight or 45 degree tting. For more information on how to

help prevent discharge line freeze-ups, see Bendix Bulletins TCH-008-021 and TCH-008-022 (available on www.bendix.com). Shorter discharge line lengths or insulation may be required in cold climates.

The air dryer contains a lter that collects oil droplets, and a desiccant bed that removes almost all of the remaining water vapor. The compressed air is then passed to — and stored in — the air brake service (supply) reservoir. The oil droplets and the water collected are automatically purged when the governor reaches its “cut-out” setting.

For vehicles with accessories that are sensitive to small amounts of oil, we recommended installation of a Bendix® PuraGuard® oil coalescing lter, designed to further minimize the amount of oil present.

Discharge Line

Compressor

Optional “Ping” Tank

Air Dryer

Governor

(Governor plus Synchro valve for the

Bendix® DuraFlo 596™ Compressor)

The Air Brake Charging System supplies the

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.

Service Reservoir

(Supply Reservoir)

Reservoir Drain

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

Recom- Recom- Acceptable Typical Discharge mended mended Reservoir Compressors Line Air Dryer Reservoir Oil Contents No. of Spec'd Cartridge Drain at Regular

Vehicle Used for:

Axles Replacement1 Schedule2 Drain Interval

Low Air Use

Compressor with less than 15% duty cycle

e.g. Line haul single trailer

w/o air suspension, air over

hydraulic brakes.

Compressor with up to 25% duty cycle

e.g. Line haul single trailer

with air suspension,

school bus.

High Air Use

Compressor with up to 25% duty cycle

less

550 air compressor

Tu-Flo

air compressor

Bendix

BA-921

e.g. Double/triple trailer, open

highway coach/RV, (most)

pick-up & delivery, yard or

terminal jockey, off-highway,

construction, loggers, concrete

mixer, dump truck, re truck.

Compressor with up to 25% duty cycle

less

Bendix

750 air compressor

Tu-Flo

air compressor

™

Bendix

e.g. City transit bus, refuse,

bulk unloaders, low boys,

urban region coach, central

tire ination.

less

, or DuraFlo 596

BA-922

Column 2 Column 3 Column 4 Column 5

I.D.

1/2 in.

For oil carry-over

control4 suggested

5/8 in. 9 ft.

For oil carry-over

control4 suggested

Length

6 ft.

upgrades:

9 ft.1/2 in.

upgrades:

Every 3

Years

Recommended

Every

Month -

Max of every

90 days

5/8 in. 12 ft.

1/2 in.

12 ft.

Every 2

For oil carry-over

control4 suggested

upgrades:

Years

5/8 in. 15 ft.

Every

Month

5/8 in.

12 ft.

Every

For oil carry-over

control4 suggested

upgrades:

Year

3/4 in. 15 ft.

BASIC test acceptable

range:

3 oil units

per month.

See

appendix

For the Bendix® BASIC™ Test Kit,

order

Bendix

P/N

5013711

BASIC test acceptable

range:

5 oil units

per month.

See

appendix

Bendix

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. 4 To counter above normal temperatures at the air dryer inlet, (and resultant oil-vapor passing

upstream in the air system) replace the discharge line with one of a larger diameter and/

or longer length. This helps reduce the air's temperature. If sufcient cooling occurs, the

oil-vapor condenses and can be removed by the air dryer. Discharge line upgrades are not covered under warranty. Note: To help prevent discharge line freeze-ups, shorter

discharge line lengths or insulation may be required in cold climates. (See Bendix Bulletins TCH-008-021 and TCH-008-022, available on www.bendix.com.)

5 For certain vehicles/applications, where turbo-charged inlet air is used, a smaller size

compressor may be permissible.

Note: Compressor and/or air dryer upgrades are recommended in cases where duty cycle is greater than the normal range (for the examples above).

For Bendix® Tu-Flo® 550 and 750 compressors, unloader service is

recommended every 250,000 miles.

Air Brake Charging System Troubleshooting

How to use this guide:

Find the Symptom(s) that you see, then move to the right to nd 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.

GENERAL SAFETY GUIDELINES

WARNING! PLEASE READ AND FOLLOW THESE INSTRUCTIONS

When working on or around a vehicle, the following guidelines should be observed AT ALL TIMES:

▲ Park the vehicle on a level sur face, apply the

parking brakes and always block the wheels. Always wear personal protection equipment.

▲ Stop the engine and remove the ignition key

when working under or around the vehicle.

When working in the engine compartment,

the engine should be shut off and the ignition

key should be removed. Where circumstances

require that the engine be in operation, EXTREME CAUTION should be used to prevent personal

injury resulting from contact with moving,

rotating, leaking, heated or electrically-charged components.

▲ Do not attempt to install, remove, disassemble

or assemble a component until you have read, and thoroughly understand, the recommended procedures. Use only the proper tools and observe all pr ecautions pertainin g to use of those tools.

▲ If the work is being performed on the vehicle’s

air brake system, or any auxiliary pressurized air systems, make certain to drain the air pressure from all reservoirs before beginning ANY work on the vehicle. If the vehicle is equipped with a

Bendix

AD-IS® air dryer system, a Bendix® DRM™ dryer reser voir module, or a Bendix® AD-9si™ air dryer, be sure to drain the purge reservoir.

▲ Following the vehicle manufacturer’s

recommended procedures, deactivate the electrica l system in a manner that safely removes all electrical power from the vehicle.

▲ You should consult the vehicle manufacturer's operating and service manuals, and any related literature,

in conjunction with the Guidelines above.

TO AVOID PERSONAL INJURY OR DEATH:

Look for:

Normal - Charging system is working within normal range.

Check - Charging system needs further investigation.

▲ Never exceed manufacturer’s recommended

pressures.

▲ Never connect or disconnect a hose or line

containing pressure; it may whip. Never remove a component or plug unless you are cer tain all system pressure has been depleted.

▲ Use only genuine Bendix

parts, components and kits. Replacement

hardware, tubing, hose,  ttings, etc. must be of

equivalent size, type and strength as original

equipment and be designed speci cally for such

applications and systems.

▲ Components with stripped threads or damaged

parts should be replaced rather than repaired. Do not attempt repairs requiring machining or

welding unless speci cally stated and approved

by the vehicle and component manufacturer.

▲ Prior to returning the vehicle to service, make

certain all components and systems are restored to their proper operating condition.

▲ For vehicles with Automatic Traction Control

(ATC), the ATC function must be disabled (ATC indicator lamp should be ON) prior to pe rforming any vehicle maintenance where one or more wheels on a drive axle are lifted off the ground and moving.

▲ The power MUST be temporarily disconnected

from the radar sensor whenever any tests USING A DYNAMOMETER are conducted on a Bendix

Wingman® Advanced™-equipped vehicle.

brand replacement

Symptom: What it may indicate: What you should do:

1.0 Oil Test Card results

Not a valid test.





Bendix® BASIC™ Test use this cup to

Discontinue using this test. Do not use this card test to diagnose compressor "oil passing" issues. They are subjective and error prone. Use only the Bendix Air System Inspection Cup (BASIC) test and the methods described in this guide for advanced troubleshooting.

The Bendix BASIC test should be the

denitive method for judging excessive

oil fouling/oil passing. (See Appendix, on page 17 for a flowchart and expanded explanation of the checklist used when conducting the BASIC test.)

measure

"oil units"

Symptom: What it may indicate: What you should do:

2.0 Oil on the outside of the compressor

2.1 Oil leaking at compressor / engine connections:

2.2 Oil leaking from compressor:

Engine and/or other accessories leaking onto compressor.

(a)Leak at the front or rear (fuel

pump, etc.) mounting ange.

(b) Leak at air inlet tting.

(d) Loose/broken oil line ttings.

(a) Excessive leak at head gasket.

(b) Leak at bottom cover plate.

(d) Leak through crankcase.

Find the source and repair. Return the vehicle to service.

Repair or replace as necessary. If the

mounting bolt torques are low, replace the gasket.

Replace the tting gasket. Inspect inlet hose

and replace as necessary.

Replace gasket or tting as necessary to

ensure good seal.

Inspect and repair as necessary.

Go to Test 1 on page 14.

Reseal bottom cover plate using RTV

silicone sealant.

Replace compressor.

(a)



3.0 Oil at air dryer purge/exhaust or surrounding Area

If unable to tell source of leak.

Head gasket (a)

and rear ange



gasket (c)

(c)

Air brake charging system functioning normally.

locations.

Clean compressor and check periodically.

Air dryers remove water and oil from the air

brake charging system.

Check that regular maintenance is being

performed. Return the vehicle to service. An optional kit (Bendix piece number 5011327 for the Bendix® AD-IS® or AD-IP® air dryers, or 5003838 for the Bendix® AD-9® air dryer) is available to redirect the air dryer exhaust.

Symptom: What it may indicate: What you should do:

4.0 Oil in supply or service reservoir (air dryer installed)

(If a maintained Bendix® PuraGuard® system lter or Bendix® PuraGuard®

oil coalescing lter

is installed, call 1-800-AIR-BRAKE (1-800-247-2725) option 2 and speak to a Tech

Team member.)

See Table A, on page 3, for maintenance schedule information.

Maintenance

(a) If air brake charging system

maintenance has not been performed.

That is, reservoir(s) have not been

drained per the schedule in Table A on page 3, Column 4, and/or the air dryer maintenance has not been performed as in Column 3.

(b) If the vehicle maintenance has

been performed as recommended in Table A on page 3, some oil in the reservoirs is normal.

(a)

Drain all air tanks (reservoirs) into the Bendix® BASIC™ test cup. (Bendix kit P/N 5013711).

Duty cycle too high

Drain all air tanks and check the vehicle

at next service interval using the Bendix® BASIC test. See Table A on page 3, column 3 and 4, for recommended service schedule.

Drain all air tanks into Bendix BASIC test

cup (Bendix Air System Inspection Cup).

If less than one unit of reservoir contents

is found, the vehicle can be returned to service. Note: If more than one oil unit

of water (or a cloudy emulsion mixture) is present, change the vehicle's air dryer, check for air system leakage (Test 2, on page 14), stop the inspection and check 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, use the BASIC cup chart on the label of the cup to determine if the amount of oil found is within the acceptable level.

 If within the normal range, return the

vehicle to service. For vehicles with accessories that are sensitive to small amounts of oil, consider a Bendix® PuraGuard® oil coalescing lter.

 If outside the normal range go to

Symptom 4.0(c).

Also see Table A on page 3, Column

3 for recommended air dryer cartridge replacement schedule.

(d) Compressor may be undersized

for the application.

The duty cycle is the ratio of time the compressor spends building air to total engine running time. Air compressors are designed to build air (to "run loaded") up to 25% of the time. Higher duty cycles cause conditions that affect air brake charging system performance which may require additional maintenance. Factors that add to the duty cycle are: air suspension, additional air accessories, use of an undersized compressor, frequent stops, excessive leakage

from ttings, connections, lines, chambers or valves, etc.

Go to

Test 2 on page 14.

See Table A Column 1, on page 3 for

recommended compressor sizes.

If the compressor is "too small" for the

vehicle's role (for example, where a vehicle's use has changed or service conditions exceed the original vehicle or engine OE spec's) then upgrade the compressor. Note: The costs incurred (e.g. installing a larger capacity compressor, etc.) are not covered under original compressor warranty.

If the compressor is correct for the

vehicle, go to Symptom 4.0 (e).

+ 14 hidden pages

Bendix Commercial Vehicle Systems TROUBLE SHOOTING COMPRESSOR User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual