Sub-Headings Safety 2 s 2 Cautions 2 Notes 2 Introduction 2 General Specifications 2 Engine 2 Coolant 2 Routine Maintenance 2 Hose Connections 4 Radiator, Charge Air and Heater Cores 4 Cooling System Leaks 4 Mounting Hardware 4 Cooling Fan 4 Water Filter 5 Engine Thermostat 5 Engine Coolant 6 Testing Coolant Mixture 7 General Operation of Cooling System 8 Heat Control and Monitoring 8 Circulation 8 Low Coolant System 8 Charge Air 9 Water Pump 9 Surge Tank 9 Shutter Assembly 9 Routine Maintenance 9 Troubleshooting and Diagnostics 9 Radiator Removal Procedure 10 Draining the Cooling System 10 Removing Components 10 Installation 11 Cooling System Table of Contents Figures Figure 1 Cooling System 3 Figure 2 Mounting Bolt 5 Figure 3 ISB Engine Trim 6 Figure 4 Cooling Hoses 7 Figure 5 Hydraulic Detail 12 Figure 6 Air Operated Shutters 12 Section 040 Cooling System 1
TC Cooling System Safety The purpose of this summary is twofold. First, it is to help ensure the safety and health of individuals performing service on this Blue Bird product. Second, it is to help ensure the protection of equipment. Before performing any service on the TC Series bus, individuals should read and adhere to the applicable warnings and cautions located throughout this service manual. The anti-freeze and water mixture in the cooling system is toxic. It is also a skin irritant and an eye irritant. Always exercise caution when working around anti-freeze. Use appropriate protective gear, including gloves, long sleeve and eye protection. Releasing the pressure on a hot system can result in burns. Always release the pressure on the system very slowly, using the vent cap before attempting to remove the radiator cap. Always work in a well-ventilated area. s s apply to a procedure or practice that, if not correctly adhered to, could result in injury or death. Particular attention should be paid to sections of this manual where warnings appear. Cautions Cautions apply to a procedure or practice that, if not correctly adhered to, could result in damage to or destruction of equipment. Notes Notes are generally used to explain, clarify or otherwise give additional insight for a given subject, product or procedure. Please note that on occasion, notes may also be used to alert individuals of potential hazards. Introduction This section contains maintenance and repair procedures for the cooling system on a Blue Bird TC Series bus, equipped with a Cummins ISB engine. General Specifications Cummins ISB Engine Coolant capacity 15.3 quarts Thermostat (fully open) 190º Pressure cap 10 psig. Note The actual capacity of your cooling system will vary, depending on the heater options installed on the vehicle. Coolant Specification 50% water and 50% ethylene glycol based antifreeze is typical. The solution may be adjusted up to 60% ethylene-glycol and 40% water for temperatures below -30º F (-37º C). SCA 4 can be used as a supplemental cooling additive, if needed. Note For routine maintenance, allow the system to cool to the point where you can lay your hand on the engine without serious discomfort. Routine Maintenance Routine maintenance is generally confined to periodically checking the coolant level and adding small amounts of coolant, if 2 Section 040 Cooling System
necessary. You should also inspect the connections and fittings in the system if coolant is required frequently. 1. Check the coolant reservoir (surge tank) for cracks. Figure 1. 2. Check all the hose clamps for tightness; heat in the system may cause the connections to become loose. 3. Check the coolant level in the surge tank by observing the sight glass. Figure 1. If liquid is visible in the sight glass, there is adequate coolant in the system. If not, add coolant mixture to the surge tank. 4. If the surge tank is empty, or nearly empty, and the low coolant warning has not activated, check the low coolant warning-sensor for contamination or corrosion before adding coolant. Figure 1. Clean as necessary. Figure 1 Cooling System Section 040 Cooling System 3
If the low coolant warning system still does not activate: 1. Check the wiring and connections in the warning circuit. 2. Replace the sensor if necessary. Figure 1. When the low coolant warning activates properly, service the system with coolant and check for leaks as listed in the instructions above. large objects from the space between it and the radiator. This will require removal of the radiator, air charge, shroud and shutter assembly. Cooling System Leaks Cooling system leaks are important and must be repaired as soon as they are detected. If the operations outlined here fail to stop the coolant loss, consult the engine service manual for possible repairs. Hose Connections Hose connections should be checked frequently. They should be tightened as necessary to prevent coolant loss. Hose clamps used on silicon hoses in the system may require tightening at several intervals after installation, when the vehicle is new or when it has been repaired. This is normal due to the compression characteristics of new silicon hoses. Replace any hose that appears cracked, swollen or deteriorated in any way. Radiator, Charge Air, and Heater Cores Check the radiator core, the charge air core, and the heater core(s) at frequent intervals. Clear any accumulation of dirt or foreign material that may impede the flow of air around the system. Check carefully for leaks in these areas as well. Check carefully in the area between the radiator and the charge air cooler. It is possible for foreign material to become lodged in the space between the two cores, causing a loss of cooling efficiency. Clean the cores with a low-pressure air hose. Sometimes, a water hose can help dislodge objects and remove heavy accumulations of dirt. In some extreme cases, it may be necessary to remove the charge air cooler to remove Mounting Hardware Inspect and maintain all the cooling system hardware frequently. Tighten mounting fasteners as necessary to minimize vibration. Figure 1, Figure 2, Figure 5 and Figure 6. Cooling Fan The cooling system fan is driven with a hydraulic motor. Verify the engine is not running and the battery is disconnected. 1. Inspect for adequate clearance of the fan blades at the radiator core, and between the fan blades and the shroud. Look for areas of wear on the fan blades and/or the radiator core and shroud. Carefully turn the fan by hand, to observe whether it turns without rubbing or obstruction. When these inspections detect nothing unusual: 2. Connect the battery and start the engine. 4 Section 040 Cooling System
Figure 2 Mounting Bolt 3. Observe that the fan turns normally and there is no unusual noise or squeal during normal operation. 4. Observe the fan motor while operating to ensure there is no oil leak or vibration apparent. Water Filter If this vehicle is equipped with a filter in the coolant system, inspect it frequently to prevent blockage and subsequent damage to the engine. Replace as necessary to maintain normal coolant flow. Engine Thermostat If the engine temperature, as indicated by instrument panel gauges, is out of the normal operating range, remove the thermostat and check it for proper operation. Engine coolant is a mixture of water and ethylene glycol. This material is toxic and is harmful to skin, eyes and lungs. It can also cause allergic reactions in humans. Always wear protective gear, including eye protection, when working with this substance. 1. Drain the coolant from the radiator, to a level below the top of the engine block. Figure 4. Capture the coolant in a suitable container for possible re-use. To minimize air in the system, be sure to close the heater lines at the transmission oil cooler and at the rear of the engine block. Figure 3. 2. Loosen and remove hose clamp at the top of the engine. Figure 3. 3. Remove the thermostat with a suitable tool. 4. Test or replace the thermostat with a new one of the proper rating. (The thermostat should fully open at 190 F or 88 C.) 5. Replace the radiator hose and torque the clamp to 10 in lb (1 N m) when reusing the old hose. Torque to 38-42 in lb (4-5 N m) when using new hose. Section 040 Cooling System 5
A defective thermostat that remains closed, or only partly opens, can cause the engine to run hot. A thermostat that is stuck open will cause the engine to run below the normal operating range. Either condition can lead to shortened engine service life. Engine Coolant Exercise caution when working with engine coolant. Anti-freeze mixtures can cause allergic reactions in humans. Always use appropriate protective gear, including gloves and eye protection. Hot engine coolant can cause severe burns. Use the vent to slowly release the pressure before removing the radiator cap. Always dispose of engine coolant mixture in accordance with applicable local, state and federal laws. Ethylene glycol is toxic and presents a danger to the environment. When you drain the system, it is best to refill with new coolant, mixed in accordance with instructions. If you intend to re-use the old coolant, be sure to capture it in a clean, suitable container, and keep it sealed to prevent contamination. The engine in this vehicle should be operated with the appropriate coolant mixture, year round. This will prevent damage from freeze and boil-over, and provide protection for seals and hoses. A 50/50 mix of water and ethylene glycol based anti-freeze provides protection down to -34 F (-36 C). For operation in lower temperatures, a 40% water mix is permissible. For extremely high ambient operating conditions, Supplemental Cooling Agent (SCA-4) may be used in accordance with the manufacturer's instructions. Figure 3 ISB Engine Trim 6 Section 040 Cooling System
Figure 4 Cooling Hoses Testing Coolant Mixture The engine should be near operating temperature. Fill the tester several times to warm it up before taking a reading. Use the vent to slowly remove pressure from the system before removing the radiator cap. Engine coolant mixture is toxic and is an eye and skin irritant. Protective gear should be used when working with this substance. Section 040 Cooling System 7
To ensure proper protection, always check the mixture when adding water or antifreeze to the system. Be sure the tester is warm before reading. Observe the instructions of the tester manufacturer for best results. the Electronic Control Module (ECM) to maintain optimum operating conditions in the engine. For more specific detail on the operation of the ECM, refer to the appropriate engine service manual. The wiring diagram for the electrical circuits of the monitoring system is located in the chassis electrical section of this manual. General Operation of the Cooling System The cooling system consists of the radiator, a surge tank (de-aeration tank), a fan (driven by a hydraulic motor), a water pump and the coolant. This system will cool the engine over the entire range of normal operating conditions for which the vehicle is designed. The cooling system on the Blue Bird Bus is designed to cool the transmission as well as the engine. The system is also the source of heat for the passenger compartment. Heat Control and Monitoring Heat control and monitoring are accomplished by circulation of the coolant liquid through the system. The water pump provides coolant flow and pressure; flow is regulated by the thermostat, and temperature read out is provided by a heat sensor. Control of the shutters (if so equipped) is provided by Alarmstats that control an actuator to open and close the shutters, as necessary. The low coolant level sensor located in the surge tank, sometimes referred to as the deaeration tank, monitors coolant level. Figure 1. If the coolant level drops below the sensor for more than about 3 seconds, the coolant low level warning system will alert the driver by turning on a warning light on the instrument panel, and sounding an alarm. The coolant is monitored by a temperature sensor, which causes the operating temperature to be displayed on the driver's instrument panel. This data is also used by Circulation Starting at the engine, coolant flows from the water pump through the engine oil cooler. From there, it goes through the water jacket of the engine to the thermostat. If the temperature is below the proper operating range, the main flow of coolant stops. To prevent damage to the water pump from loosing fluid flow, fluid from the surge tank continues to flow to it. When the coolant temperature has risen to the point that it opens the thermostat, coolant flows into the top of the radiator and makes its way down through the core. Heat is transferred to air passing over the fins, and the coolant is delivered to the transmission fluid heat exchanger through the return opening at the bottom of the radiator. A pipe and ball valve, located on the upper rear of the engine is used to divert this flow into the heating system to provide heating for the passenger and driver compartment. Figure 3. Coolant, re-routed in this way, is returned to the system through a ball and "T" valve assembly located at the transmission heat exchanger. Figure 4. Low Coolant System A coolant level sight glass is located on the surge tank. This provides for a visual indication of the amount of coolant in the system. An electronic low level warning is provided to warn the driver while the bus is being operated. Figure 1. 8 Section 040 Cooling System
The low level sensor is electrically conductive while covered with engine coolant, but "opens" when not covered with fluid. There is a built-in three-second delay in the circuit to prevent false indications when the fluid sloshes during normal operation. After current flow to the ECM is interrupted for more than three seconds, it sends a signal to the instrument light panel that turns on the warning light and sounds an alarm. The low coolant-warning module is located next to the relay panel, behind the panel door at the driver's side windshield wiper. Shutter Assembly Shutters are installed, as an option, on the radiator/charge air cooler assembly to assist in warming the engine in colder weather. Shutters are an assembly of pivoting blades that close to restrict air flow when the engine temperature is below normal operating range. These blades, similar to venetian blinds, are operated by either air pressure or, hydraulically, by oil pressure. They are controlled by Alarmstats (sensors) located on the engine and manifold. See Figure 5 for hydraulic detail or Figure 6 for air operated shutters. Charge Air To improve fuel consumption, lower emissions, and, in some cases, to help increase horsepower, the engine intake air is cooled after being compressed by the turbocharger. The hot, compressed air is routed through a heat exchanger similar to a radiator. Heat is transferred to the surrounding air by cooling fins in the same way engine coolant is cooled by the flow of air over the radiator. Figure 2. The charge air cooler is attached to the outboard side of the radiator so that air passes through it first. Water Pump The water pump is an internal part of the engine. Refer to the appropriate engine service manual for specific details on repair or replacement of the water pump, and for a description of its operation. Surge Tank The surge tank stores coolant fluid for use as the system needs it. Sometimes called the de-aeration tank, it is located in front of and above the engine. Routine Maintenance Shutters require no lubrication but they should be kept clean by removing debris and dirt to allow them to operate as designed. Periodic inspection and tightening of hardware is recommended. You should watch for leaks and loose or missing parts. Troubleshooting and Diagnostics If the shutters do not open or close as they should: 1. Visually check for binding or blockage by foreign material. 2. Inspect the air or hydraulic lines for breaks or leaks at fittings. 3. Check operation of the solenoid, by removing the electrical plug and applying 12 volts to one of the pins at the solenoid. Apply ground potential to the other pin. If the solenoid operates, it is good. If it does not operate, it should be replaced. If the solenoid operates but the shutters fail to open: Disconnect the actuator from the shutter blades and attempt to operate the blades manually. The shutters Section 040 Cooling System 9
are held open by spring tension, but they may be operated with a little effort. If they will not operate, locate the reason; foreign material, a bent or broken part, etc. If the shutter blades move by hand, then you must check the actuator. Leaving the actuator disconnected, apply air or hydraulic pressure to the actuator by manually operating the solenoid with the jumper used in step 3 above. If all these procedures indicate nothing is wrong, the Alarmstat is probably inoperative. There is no reliable test procedure available in the average repair shop to test an Alarmstat, so substitution may be the best alternative. An Alarmstat has an expected useful life of up to 750,000 cycles; hence, they rarely wear out. the unit under repair, refer to the appropriate engine service manual. It is desirable to isolate the heater lines when draining the system, so that refilling is easier, and to avoid air in the system when refilling. Figure 3 and Figure 4. Both should be turned off before draining the system. A "bleed" valve is located near the surge tank to help get air out of the system if necessary. 1. Turn the pipe and ball valve located at the top rear of the Cummins ISB engine to the off position. Figure 3. 2. Turn off the ball valve at the "T" connection on the transmission cooler. Figure 4. 3. Remove the surge tank filler cap. Figure 1. 4. Open the drain-cock (drain valve) located in the return hose at the bottom of the radiator, near the transmission oil heat exchanger. Radiator Removal Procedure Coolant mixture (anti-freeze) is toxic and is an irritant to skin, eyes and to the respiratory system. It can also cause allergic reactions in humans. Appropriate protective gear is necessary when working with this material. Always work in a wellventilated area. Engine coolant can be very hot. Exercise caution when opening the system. Always use the vent to slowly release pressure before removing the radiator cap. Draining the Cooling System The system is provided with a drain point, located on the return hose at the bottom of the radiator. Figure 4. Some engine options also provide a drain point on the engine. For details of the engine option in Always drain the coolant mixture into a suitable container. Keep it sealed to prevent contamination before reuse. It is better to use a new mixture of anti-freeze when filling the system, but it is possible to use the old coolant if it is clean and not discolored. Removing Components Extensive component removal is necessary to remove the radiator. 1. Remove the hood (inside). Refer to Figure 1 in Section 060 Engine. 2. Remove bumper. Refer to Figure 1 in Section 060 Engine. Note If the unit is equipped with tow hooks, it will be necessary to remove the special cross-brace as well. 10 Section 040 Cooling System
3. Remove both the upper and lower grills. Refer to Section 060 Engine (Figure 3) for detailed procedures. After draining the system of coolant, see instructions above. Start at the top-most connection. 1. Loosen the clamp at the outside top of the radiator and remove the small hose that runs to the surge tank. It is not necessary to remove the surge tank unless it needs replacement. 2. Loosen the radiator hose clamp at the thermostat nipple and remove the hose. Figure 3. 3. Loosen and remove the charge air hoses at the (reducer) top inside. 4. Loosen the clamp at the bottom of the radiator, and remove the bottom hose. 5. Put the captured fluid in a safe place before proceeding. Note If the unit is equipped with radiator shutters, exercise caution not to damage the shutter solenoid control unit. It is attached to the inside top-left corner of the radiator, as seen from inside the bus. Remove the lines from the control unit before continuing. 6. Loosen the nuts on the radiator isolators. Figure 1. Remove them from both sides of the radiator. All four nuts may be removed; the radiator will stay in place. The radiator, charge air, shroud and shutters (if so equipped) are removed as an assembly. Depending on whether there is a shutter assembly, the unit weighs from approximately 175 to 225 lbs. A suitable hoist must be used to lift the radiator assembly from the front of the bus. The entire unit is resting on the four bolts that attach it to the bus. Caution Use care to avoid damage to the fan while removing the radiator assembly. Be careful not to damage the cooling fins as well. 7. Lift the radiator out of the chassis after tilting the top toward the front. 8. Remove any hoses that need replacing before installing the repaired radiator. 9. If necessary, it is now possible to disassemble the radiator, shroud, charge air, and shutter assembly. Figure 1 and Figure 2. Installation Installation of the radiator/charge air and shroud assembly is accomplished in the reverse order of the removal instructions above. Fasteners should be tightened to a torque value of 50 ft-lbs. (68 N m). Figure 2. Fasteners should be tightened to a torque value of 35-50 ft-lbs. (47-68 N m). Figure 2. Tighten all hose clamps and fasteners to comply with applicable torque values as listed in Section 005 Introduction of this manual. Section 040 Cooling System 11
Figure 5 Hydraulic Detail Figure 6 Air Operated Shutters Back to Top 12 Section 040 Cooling System