a3 cooling systems - central states bus sales, inc. cooling systems 040-1 ... cat. 3126 engine...

A3 Cooling Systems

040-1

A3 Cooling Systems

Table of Contents

Table of Contents ...........................................1List of Figures.................................................1Safety ..............................................................1Introduction....................................................1General Specifications....................................2Types of Coolant.............................................2Coolant Capacities .........................................3Routine Maintenance .....................................4Description of Operation................................5System Components .......................................6Removal and Replacement Procedures .........7Coolant System Shutters ..............................14

List of FiguresFigure 1.1—Cooling System, A3FE, ISB

Engine (1 of 2) ........................10Figure 1.2—Cooling System, A3FE, ISB

Engine (2 of 2) ........................11Figure 2—Cooling System, A3RE, ISB

Engine .......................................12Figure 3—Cooling System, A3RE, ISC

Engine .......................................13Figure 4—Shutter Assembly, Hydraulic,

A3FE .........................................15Figure 5—Shutter Assembly, Air, A3FE.....16Figure 6—Shutter Assembly, Air, A3RE ....17

SafetyThe purpose of this safety summary is to ensure thesafety and health of personnel and the protection ofequipment.

All users of this publication shall read, understand,and apply this safety summary when performingmaintenance and operating procedures.

WARNINGS and CautionsAll users of this publication shall read, andunderstand, all WARNINGS and Cautions.

WARNINGS REFER TO A PROCEDUREOR PRACTICE, THAT, IF NOT

CORRECTLY OBSERVED, COULDRESULT IN INJURY OR DEATH.

Cautions see to a procedure or practice, that,if not correctly observed, could result indamage to or destruction of equipment.

IntroductionThis section contains information pertaining to thecooling systems on Blue Bird All American schoolbuses equipped with Cummins ISB, ISC, andCaterpillar 3126 engines.

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RAPID VENTING OR RAPID REMOVALOF RADIATOR CAP WHILE THEENGINE IS HOT WILL ALLOW

COOLANT TO SPRAY OUT.TO PREVENT SERIOUS BURNS SLOWLY

VENT PRESSURE, THEN REMOVERADIATOR CAP.

ANTI-FREEZE IS TOXIC TO SKIN ANDEYES. SKIN AND EYE PROTECTION IS

REQUIRED.AVOID REPEATED OR PROLONGED

CONTACT. DRAIN COOLANT FLUID INA WELL-VENTILATED AREA.

PROPERLY DISCARD ANTIFREEZETHAT IS DRAINED FROM COOLING

SYSTEM.ANTI-FREEZE CAN CAUSE AN

ALLERGIC REACTION TO HUMANS.

General SpecificationsISB Engine

Coolant capacity - 15.3 qts.Thermostat (fully open)- 190°FPressure cap - 15psi

ISC EngineCoolant capacity - 13.0 qts.Thermostat (starts to open)- 181°F(fully open)- 203°FPressure cap - (minimum allowable) 7.0 psi

Cat. 3126 EngineCoolant capacity - 14.0 qts.Thermostat (starts to open)- 181°F(fully open)- 203°FPressure cap - (minimum allowable) 7.0 psi

Type(s) of CoolantISB Engine

• 50% water and 50% ethylene-glycol baseantifreeze.

• May be diluted to as much as 40% waterand 60% antifreeze for temperaturesbelow -34°F (-37°C).

• DCA-4 should be used as a supplementalcooling additive.

ISC Engine• 50% water and 50% ethylene-glycol base

antifreeze.• May be diluted to as much as 40% water

and 60% antifreeze for temperaturesbelow -34°F (-37°C). Never exceed 30/70mix.

• DCA-4 must be used as a supplementalcooling additive.

Cat. 3126• 50% water and 50% ethylene-glycol base

antifreeze• May be diluted to as much as 40% water

and 60% antifreeze for temperaturesbelow -34°F (-37°C). Never exceed 40/60mix.

• DCA-4 must be used as a supplementalcooling additive.

For information regarding pump flow rate, seeappropriate engine manual.

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Coolant Capacities, A3FE and A3RE

Opt. No. Description Capacity (qts)Std Radiator, de-aeration tank, & hose 11-12Std 90K btu A3 front heater 3.19Std 12K btu driver’s heater 0.251325 50K btu front underseat heater 1.561330 50K btu rear underseat heater 1.561332 50K btu rear RH underseat heater 1.561336 80K btu front underseat heater 2.341342 80K btu rear underseat heater 2.34Std per 1 foot of heater hose 0.17

Coolant calculation example:Unit with ISB Cummins engine & options 1325 &1342:

Drivers heater (std) 0.25Front heater (std) 3.19Option 1325 1.56Option 1342 2.3476 ft. of hose @ .17 qt/ft 12.92

20.26 qt. in theheating system

Engine cooling system 11.5Engine 13.0

44.76 qt. Totalcoolant capacity

(Roughly equivalent to 11.2 gal.)

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Routine MaintenanceRoutine maintenance generally consists of checkingand replenishing coolant, flushing the system, andperiodic changing of the coolant. For detailedrequirements and for procedures to accomplish thoserequirements, refer to the appropriate enginemanufacturer’s manual.

Surge Tank Coolant Level

RAPID VENTING OR RAPID REMOVALOF RADIATOR CAP WHILE THEENGINE IS HOT WILL ALLOW

COOLANT TO SPRAY OUT.TO PREVENT SERIOUS BURNS SLOWLY

VENT PRESSURE, THEN REMOVERADIATOR CAP.

Check the coolant level at the surge tank byobserving the level in the sight glass. If liquid isvisible in the sight glass, the system containsadequate quantity of fluid. If coolant is not visible inthe sight glass, add coolant as necessary to bring thelevel up to the level of the sight glass. If the surgetank is empty or nearly empty, and the low coolantwarning has not activated, check the low coolantsensor for contamination or corrosion. Clean orreplace the sensor as necessary. If the warningsystem does not activate after cleaning or replacingthe sensor, check wiring and connections in the lowcoolant warning system. If all wires and connectionsappear to be ok, replace the low coolant warningmodule. After correcting any faults in the lowcoolant warning system, be sure to adequatelyservice the system with coolant.

Hose ConnectionsHose connections should be checked and tightenedas necessary. Hose clamps used on silicone hoses inthe cooling system may require tightening at severalintervals after initial tightening. This is a normalcompression characteristic of new or replacementsilicone hoses. Check and re-tighten clamps untilsubsequent checks verify that there is no need forfurther tightening. Replace cracked, swollen, ordeteriorated hoses as necessary.

Radiator, Charge Air, and Heater CoresCheck the radiator core, charge air cooler core, andheater cores regularly for leaks and for accumulationof dirt or other foreign materials that may obstructthe flow of air. In addition, be sure to check the areabetween the charge air cooler and the radiator.Sometimes obstruction may occur between the twocores. Clean the cores with an air hose using low-pressure air. It may be necessary to use water toremove heavy accumulations from the cores. Insome severe cases, it may be necessary to removethe charge air cooler in order to gain access to thearea between it and the radiator.

Cooling System LeaksRepair all cooling system leaks as soon as they aredetected. If they are not beyond repair, mostradiator, charge air cooler, and heater core leaks canbe repaired locally using common radiator repairtechniques. Refer to the appropriate engine servicemanual for procedures on repairing or replacingleaking cylinder head gaskets, and for the removaland replacement of water pumps.

Mounting HardwareInspect radiator and charge air cooler mountinghardware. Tighten mounting and attaching bolts asnecessary.

Cooling FanRefer to section 170—Hydraulic Fan Drive toverify the operation of the fan. Inspect for properclearance between the fan and the radiator core andbetween the fan and the fan shroud. If a “swing-out”radiator is installed, check that the fan shroud isproperly secured. An unsecured fan shroud couldseriously damage both the fan and the radiator core.

Water FilterInspect and service any water filter as directed bythe filter manufacturer.

Engine ThermostatIf the engine operating temperature deviates fromthe normal range for that engine, remove and checkthe thermostat(s). A defective thermostat thatremains closed, or only partially open, will restrictthe flow of coolant and cause the engine to overheat.A thermostat that is stuck in the full open position,will cause the engine to run below it’s normaloperating temperature, which will eventually lead toshortened engine life.

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Engine Coolant




The buses covered by this manual have pre-mixedcoolant, appropriate to the engine manufacturer’srecommendations, installed at initial assembly. Referto the appropriate engine manufacturer for propercoolant, coolant mix ratio, and supplemental coolingadditives (SCAs). All engines used in Blue Birdbuses should have anti-freeze solution used year-round to provide freeze and boil-over protection aswell as a stable environment for seals and hoses.

General coolant recommendationsAlways maintain the proper coolant level. CheckDaily.

Overfilling a cooling system can result in theunnecessary lose of coolant and, in some cases,cause the engine to overcool, especially duringextreme cold weather operation.

The cooling system must be pressurized to preventlocalized boiling of the coolant. The system must bekept clean and leak-free. The fill cap must always beinstalled and periodically checked for properoperation.

Testing antif reeze solution




To ensure freeze protection, always test theantifreeze solution before and after adding water orantifreeze, using a standard antifreeze tester. Fill andempty the tester several times to warm it before

using. Keep the tester clean inside and out. Followthe instructions of the tester manufacturer for themost accurate results.

Description of Operation

Engine cooling systemThe system consists of the radiator, de-aeration tank,thermostat, fan, water pump and liquid coolant. Thecooling system is designed to adequately cool theengine across the entire speed and load range. Heatgenerated by the engine is transferred to the coolant,which is circulated by the water pump to theradiator. As the fan pulls air across the finnedsurfaces of the radiator, excess engine heat isdissipated to the atmosphere. Engine coolant is alsocirculated through the transmission oil cooler toremove heat from the transmission fluid. Refer the totransmission section for information on thetransmission cooler. See Figures 1.1 and 1.2 in thissection.

In addition to removing heat from the engine andtransmission, the cooling system also distributes heatin the form of warm coolant into the driver’s and busbody heating systems.

Heat control and monitoringHeat control and monitoring are accomplished by acombination of mechanical and electrical means. Athermostat, located in the engine, controls the flowof coolant into the radiator. The coolant level ismonitored by a low coolant probe mounted in thede-aeration tank. If the coolant level drops below theprobe, the low-coolant module illuminates a light toalert the driver, and turns on the low coolant tell talelight on the instrument cluster. Coolant temperatureis monitored by the coolant temperature sensor,which signals the engine ECM. For moreinformation on the low coolant and temperaturewarning systems, refer to the engine and chassiselectrical systems.

CirculationCoolant flows from the engine water pump throughthe engine oil cooler, through the cooling passagesin the engine up to the thermostat. If the temperaturehas not risen enough for the thermostat to open, themain flow of coolant stops until engine heat hasrisen enough to cause the thermostat to open. SeeFigures 3 and 4 in this section.

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To prevent the water pump from cavitation, fluidfrom the de-aeration tank is supplied to the pump.Once the thermostat opens, coolant flow continuesfrom the engine into the top of the radiator. As thecoolant flows from the top of the radiator throughthe core to the bottom of the radiator, air flowingacross the radiator causes a heat exchange to takeplace, lowering the temperature of the coolant.

After flowing out of the outlet pipe at the bottom ofthe radiator, the coolant then flows through a hose tothe transmission cooler, where a heat exchange takesplace between the coolant and the transmission’sfluid. From the transmission cooler, the coolant thenflows back to the water pump, beginning the cycleagain.

A pipe and ball valve located on the right handcorner of the engine (front for Cat. 3126 and rear forCummins engines), diverts hot coolant from theengine block out to the heater system. After passingthrough the heater cores the coolant is returned tothe system through a ball valve and ‘T’ connectionat the transmission cooler.

Low coolant warning systemA coolant level sight glass located in the surge tankprovides for visual inspection to determine coolantlevel. In addition, a low coolant warning system isinstalled to warn the driver of a low coolantcondition while operating the vehicle. Anelectrically conductive probe is located in the surgetank (de-aeration tank). As long as coolant is at alevel with the probe, current flows to a low coolantwarning module. A three-second delay is built intothe module to allow for sloshing of the coolant. Ifthe coolant falls below the probe for a period ofgreater than three seconds, then the current to themodule is broken. The module then sends a signal tothe instrument cluster that lights a telltale light andsounds a warning. The low coolant warning moduleis located next to the relay panel located behind thedriver’s side windshield wiper motor door.

Charge AirIn an effort to improve fuel consumption, to loweremissions to meet government regulations, and insome cases, to permit increased horse power, theengine intake air is cooled after it has beencompressed in the turbo-charger. The hotcompressed air is passed through a heat exchangersimilar to the radiator. A heat exchange takes placebetween the hot air in the core and the cool ambient

air passing through it. This charge air cooler isattached to the radiator so that the cool air passesthrough the charge air cooler first (in other words, onthe outside of the radiator).

System Components

Water pumpWater pumps are integral to the engine. See theappropriate engine manual for further description.

Hoses, clamps, and fittingsHoses, clamps, and fittings vary according to option,coolant hoses may be either rubber or silicone.Based on the type of hose, the clamps and theirtorque values will be different. Mixing differenthoses with the wrong type of clamps could damagethe hose or cause leaking.

RadiatorThe radiator is located directly in front of the enginefacing forward on forward engine units. For rearengine buses, the radiator is located to the left of theengine, and faces the street side of the bus. SeeFigures 2 and 3 in this section.

Surge tank (de-aeration tank)The surge tank (de-aeration tank) is attached to thebody and located in front of and directly above theengine on a forward engine unit, and behind and tothe left of the engine on a rear engine unit.

Low coolant warning systemThe low coolant warning system is made up of thefollowing components:• Sensor—located in the surge (de-aeration) tank.• Module—located next to the relay panel that is

behind the driver’s side wiper motor door.• Light—located in the instrument cluster.

Charge air coolerThe charge air cooler is located directly in front ofand attached to the radiator.

Heater componentsEach heater consists of valves, cores/heatexchangers, and hoses and fittings.

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Removal and Replacement ProceduresReference the diagrams at the end of this section forhelp in performing the following service procedures.




Draining and filling the cooling systemCoolant drain points are provided on the bottom ofthe radiator, and on the engine (refer to specificengine manual for location).

With heating supply and return lines isolated, thecooling system can be drained without draining theheater lines. A bleed valve is provided near the surgetank to allow bleeding air from the heater supply andreturn lines.

Draining1. Remove the surge tank filler cap.2. Open the radiator and engine drains, capturing

coolant in suitable containers.

Filling1. Close all drain cocks.2. Slowly fill the system through the surge tank

until coolant is at the level of the filler cap.3. Start the engine and run it at “high idle” (fast

idle) until normal operating temperature isreached.

4. Return the engine to normal idle.5. Check the water level and add as necessary.6. If coolant level is very low bleed the heating

system. Refer to heater system bleeding.7. Install filler cap.

Radiator and charge air coolerThe radiator is removed as an assembly with thecharge air cooler.




Removal (Forward Engine)See Figures 1.1 and 1.2 in this section.

1. Remove the front grill panel as described insection 060—Engine.

2. Drain the cooling system as previouslydescribed.

3. Loosen the hose clamps on the charge air coolerinlet and outlet pipes and remove the hoses.

4. Disconnect all hose connections to the surgetank to the radiator.

5. Loosen the hose clamps on the radiator inlet andoutlet pipes, then remove the inlet and outlethoses.

6. Remove the mounting bolts, washers, andinsulators attaching the engine to the frame.

7. Supporting the radiator and charge air coolerwith a suitable lifting device, remove theassembly from the vehicle.

Once removed, the radiator and charge air coolermay be separated by removing the attachinghardware.

Installation (Forward Engine)1. If the radiator and charge air cooler were

separated, they must be re-connected. Torqueattaching bolts to 30±5 foot-pounds.

2. Set the radiator/charge air cooler assembly inplace on the radiator mounting points on thechassis.

3. Make sure that insulators are installed at thistime.

4. Loosely install the mounting bolts and washers.5. Loosely attach the radiator inlet and outlet pipes

and hoses.6. Torque mounting hardware.

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040-8

7. Torque hose clamps.8. Fill the cooling system as described earlier in

this section.9. Check for system leaks.

Removal (Rear Engine)

NoteFor best results, the bus should be

elevated enough to facilitate the removalof the radiator/charge air cooler assembly

from under the side of the bus.

1. Drain the cooling system as previouslydescribed, see Figures 2 and 3.

2. Loosen the hose clamps on the charge air coolerinlet and outlet pipes.

3. Remove the hoses.4. Disconnect all hose connections between the

surge tank and the radiator.5. Loosen the hose clamps on the radiator inlet and

outlet pipes.6. Remove the inlet and outlet hoses.7. Remove baffles and seals from radiator/charge

air cooler assembly.8. Remove radiator shroud assembly from the

radiator with fan and fan motor attached.

NoteDo not drain the hydraulic system.

9. Remove the mounting bolts, washers, braces andinsulators attaching the radiator to the chassis.

10. Supporting the radiator and charge air coolerfrom below, remove the assembly from thevehicle by moving it away from the engine anddown between the side of the bus and theradiator mounting platform.

Once removed, the radiator and charge air coolermay be separated by removing the attachinghardware.

Installation (Rear Engine)1. If the radiator and charge air cooler were

separated after removal, they must be re-connected. Torque attaching bolts to 30±5 foot-pounds.

2. Set the radiator/charge air cooler assembly inplace on the radiator mounting platform on thechassis.

3. Make sure that insulators are installed at thistime.

4. Loosely install the mounting bolts, washers, andbraces.

5. Prepare and install baffles and seals around theradiator and charge air cooler assembly.

6. Install radiator shroud assembly, insuring thatthere is adequate clearance between the fan andthe core. Insure that fan motor hoses are notbound, kinked, or twisted.

7. Loosely attach the radiator inlet and outlet pipesand hoses.

8. Torque mounting hardware.9. Torque hose clamps.10. Fill the cooling system as described earlier in

this section.11. Check for system leaks.

Removing only the charge air coolerThe charge air cooler can be removed separatelywithout removing the radiator or draining thecooling system.

Removal1. Forward Engine—Remove front grill panel as

describe in section 060—Engine.2. Rear engine—Remove baffles and seals from

radiator and charge air cooler assembly.

NoteFor best results, the bus should be

elevated enough to facilitate the removalof the charge air cooler from under the

side of the bus.

3. Loosen the hose clamps on the charge air coolerinlet and outlet pipes and remove the hoses.

4. While supporting the charge air cooler,disconnect the three bolts attaching the chargeair cooler to the radiator.

5. Remove the charge air cooler.

NoteRear engine bus charge air cooler is

removed by sliding the cooler down andunder the side of the bus.

Installation is the reverse of the removal process.

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Sight Glass Replacement1. Ensure that fluid level is below the sight glass.2. Twist the glass counterclockwise to remove the

glass and O-ring.3. Reverse the procedure to install a new glass.4. Check for leaks.

Surge Tank replacementSee Figures 1.2, 2, and 3.

1. Remove the surge tank fill cap.2. Drain coolant to a level so that none remains in

the surge tank.3. Disconnect and tag all electrical wires from the

low coolant probe.4. Disconnect and tag all hoses from the surge

tank.5. Remove the mounting hardware and remove the

surge tank from the engine compartment.6. Replace parts as necessary and reverse the

procedure to install the surge tank.

Heater Core Replacement

Removal1. Isolate the heater system from the cooling

system by closing the valves at the engine andoil cooler.

2. Carefully loosen the heater hose clamp at thetransmission cooler and remove the heater hose,capturing the coolant from the heater circuit in asuitable container.

3. Disconnect the heater hoses from the appropriateheater core and remove the heater core.

NoteDepending upon which type of heater coreis being removed, a seat may need to be

removed.

Installation1. Install the appropriate heater core, attach hoses,

and torque hose clamps.2. Reattach the heater hose to the transmission

cooler and torque the clamp.3. Open the isolation valves at the engine and oil

cooler.4. Service the cooling system as previously

described.5. Bleed the heater system.6. Bring the engine to operating temperature.

7. With the engine at normal idle, open the smallbleed line valve located above the radiator (bothforward and rear engine applications).







8. Observe fluid flow from the bleed line andcapture in a suitable container.

9. Add coolant to the system until a steady streamof fluid flows from the bleed line.

10. Close the bleed line valve and install the fill cap.

Water PumpReference the appropriate engine manufacturer’sinstructions.

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Figure 1.1—Cooling System, A3FE, ISB Engine (1 of 2)

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Figure 1.2—Cooling System, A3FE, ISB Engine (2 of 2)

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Figure 2—Cooling System, A3RE, ISB Engine

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Figure 3—Cooling System, A3RE, ISC Engine

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Coolant System Shutters

Description of OperationShutters are installed on the radiator/charge aircooler assembly to assist in warming the enginequicker during cold weather operations of thevehicle. Consisting of a series of pivoting blades(similar to venetian blinds), the blades close whenthe engine is cold, restricting the flow of cooling airthrough the radiator and charge air cooler.

Shutters can be located on the fan side or on theoutside of the radiator and charge air cooler package.As the engine warms, a cylinder actuates, causingthe blades to pivot open which in turn allows air toflow through the radiator and charge air cooler,resulting in the normal operation of the coolingsystem.

Two types of shutter systems are available for AllAmerican school bus. One shutter system utilizesengine oil to hydraulically actuate the cylinder, seeFigure 4. This system may be found on either air orhydraulic brake equipped vehicles. The other shuttersystem uses air from the vehicle air system, seeFigures 5 and 6. This system is only available on airbrake equipped vehicles.

In both systems, an electrical signal from the watertemperature sensor activates the shutter solenoid.The solenoid then opens to allow air or oil (asappropriate) to flow through to and operate theactuator cylinder.

Routine maintenanceThe shutters require no lubrication but must becleaned as required. This is at least every 2 years or24,000 miles, whichever occurs first. In addition,periodic visual inspections for leaks or loose ormissing parts should be conducted.

Troubleshooting and diagnostics

Shutters do not operate (open or close)1. Visually check for physical binding or blocking

of the blades.2. Visually check for cut air or hydraulic lines and

loose fittings.

3. Check for operation of the water temperaturealarmstat. Refer to section 170—Hydraulic FanDrive.

4. Check operation of the solenoid. With thesolenoid electrical plug disconnected, apply 12volts to one pin of the plug and ground the other.If the solenoid does not operate, replace thesolenoid.

5. If the solenoid is operating but the blades do notopen, disconnect the actuator cylinder from theblades. Perform the procedure in step 4 aboveand determine if the cylinder is actuating. Whenthe solenoid operates with air or hydraulicpressure on the system, the cylinder shouldextend or retract. If it does not, replace theactuating cylinder.

6. If the actuator cylinder is operating correctlywhile it is still disconnected, attempt tomanually move the blades. The blades should beheld open by spring pressure, and are closed bythe actuator. If the blades can not be moved withreasonable pressure, replace the shutterassembly.

Removal and replacementOn front engine applications with the shuttersattached to the outside of the radiator and charge aircooler package, the shutter assembly can be removedafter removing the access door and grill assembly.The radiator and charge air package does not need tobe removed.

On all other applications remove the radiator andcharge air package as described in this section, anddisconnect the shutter assembly from the removedradiator/charge air package.

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Figure 4—Shutter Assembly, Hydraulic, A3FE

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Figure 5—Shutter Assembly, Air, A3FE

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Figure 6—Shutter Assembly, Air, A3RE

a3 cooling systems - central states bus sales, inc. cooling systems 040-1 ... cat. 3126 engine...

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