This lesson will instruct students on the proper procedures needed to remove and replace a radiator, test coolant, drain and recover coolant, flush and refill the cooling system with recommended coolant, and bleed air from the system as required. Knowledge of these techniques and the skills required to correct problems associated with this task are necessary for a student to acquire if they wish to compete for high paying, high skilled jobs in an automotive repair facility. Entry level technicians need to be able to perform this task to 100% accuracy. Incorrectly performing this task can lead to drivability concerns, safety problems, or customer satisfaction issues.
Given the proper tools and instructions from a vehicle manufacturers shop manual or automotive computer software program, students will be able to remove and replace a radiator, and pass a written exam on the task with 100% accuracy by the end of the course.
SAFETY ALERT: Caution the students to never remove a radiator cap from a hot engine. Make sure it is completely cool before removing the cap.
Instruct the students to drain the cooling system before removing the radiator. To drain the cooling system: • Park the vehicle on a level surface • When the engine is cool, remove the radiator pressure cap. • Place suitable containers under the vehicle to collect the used coolant. • Open the drain valve or plug on the radiator. • Open the cooling system air bleed vent, if used. • Allow the coolant to drain completely. • Recycle or dispose of the used coolant in an approved manner.
After the coolant has been drained, instruct the students to begin removing the radiator. Disconnect the electric fan wiring harness, if used. Disconnect the upper and lower radiator hoses. Remove the fan shroud, if necessary. Remove the radiator overflow hose. Disconnect the transmission and/or engine oil cooler lines if the vehicle is equipped with these. Remove the radiator mounting brackets and carefully lift the radiator out.
Instruct the students to inspect the radiator mounting brackets and insulators before installing the radiator. Replace if needed. Install the radiator along with the fan shroud and electric fan, if used. Connect the fan wiring. Inform the students that new radiator hoses and clamps should be used unless the original parts are in very good condition.
Inform the students that flushing the cooling system is sometimes necessary. When this procedure is performed it should be done in a reverse-flow direction. This is called back-flushing. Make sure the entire cooling system, including the heater core, is flushed. Several types of flushing equipment are available. Follow the manufacturer’s instructions for use.
After the radiator is installed, instruct the student to refill the cooling system. To refill the system: • Refer to the vehicle service information for the correct antifreeze and water mix and the total amount of coolant needed. If in doubt, it is usually safe to use a 50/50 mix. • Make sure the drain plug is installed and tightened. • Add the specified amount of antifreeze before adding any water. This will ensure that the proper amount of antifreeze is in the system. In most cases the system is filled through the radiator filler neck. • Add water slowly until it is at the bottom of the filler neck. In general it is safe to use tap water. Well water or water with a high mineral content is not recommended. • Wait several minutes and check the level again. • Add more water if needed. • Replace the radiator cap.
Inform the students that when the coolant has been drained sometimes air is trapped in the cooling system. Air may be trapped in the engine block because the closed thermostat will not allow coolant to pass through. In this case the cooling system needs to be bleed. To bleed the system: • After filling the system, start the engine and allow it to run. When the thermostat opens, most of the trapped air will travel to the radiator. • Turn the engine off and allow it to cool. • Check and adjust the coolant level if needed. • Some engines require special filling and bleeding procedures. Refer to the vehicle service information for these procedures.
Inform the students that coolant must be tested to determine its freezing point. Two types of testers can be used for this: an optical tester (refractometer) and a coolant hydrometer. Both testers determine the density of the liquid being tested. To use the optical tester use an eyedropper to remove a few drops of coolant from the radiator. Open the tester cover and place a drop of coolant in the opening. Close the cover and hold the tester up to a light source while looking through the eyepiece. A direct reading of freezing protection will be visible. To use the coolant hydrometer, coolant is drawn into the hydrometer until the liquid supports the calibrated float. The point that the float(s) rise to indicates the level of freezing protection. Inform the students that it requires two differently calibrated hydrometers to test ethylene glycol vs. propylene glycol antifreezes.
Applications/Practice
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Refer to content.
Evaluation and feedback Prior to Testing or Lab Work
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Objective 1/ Formative assessment / Instructor will observe students as they practice the procedure to assure correct methods and safety practices are being followed. A checklist should be utilized to chart student progress on the task. Questioning techniques will be utilized as necessary to demonstrate student comprehension / Adaptations and/or accommodations for special needs students will be added if required.
STUDENT ASSESSMENT: (Assess student progress with performance criteria.)
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Objective 1/ Summative assessment / written test questions on stated objective / adaptation and / or accommodations for special needs students will be added if required.
IMPACT--Reflection/Analysis of Teaching and Learning: (How did students’ progress in relation to the state objectives? Was the instruction successful? Analyze samples of student work particularly that which is unsatisfactory, for the purpose of planning further instruction.)
REFINEMENT--Lesson Extension and Follow-up: (To be filled in as the lesson is modified during initial planning and/or during the teaching learning process.)
