The next day, the Teacher of Mechanization of Agriculture  brings you together and initiates a discussion about the possible reasons you think the tractor overheated and then failed to start.

After the discussion, the lecturer explains what your task will be where the causes of the failure will be looked for in the tractor’s cooling, lubrication and fuel systems.

The task of your teamwork is to identify the faults of the tractor, propose solutions and prescriptions for their elimination.

You will divide into three groups, three students per group and each group will have the team task of diagnosing and making prescriptions for repairing the designated, for that group, tractor system.

The groups will be given electronic devices and with the help of resources on the internet, you will be facilitated in finding a solution to the school tractor problem.

Participants from each group will go through the following steps in solving the problem:

• RESEARCH PHASE,
• ANALYSIS PHASE,  
• DECISION

STEP 1 : RESEARCH PHASE OF THE COOLING SYSTEM

During this phase, you students will work in a study room where each of you has a personal computer/laptop and internet. The teacher will provide you with resources to complete this step, in the form of technical information to familiarize you with the basic principles of operation and common problems and failures of the tractor system you are investigating. For basic information, you will use links on the Internet, the material from which is mostly in English. This information will also help you to complete the next two steps of the assignment. The research phase is two class periods long.. The cooling system is designed to ensure optimum engine temperature during operation. A malfunction in the cooling system results in its malfunction and engine failure. A dirty radiator surface, for example, increases the coolant temperature and overheats the engine, and this can damage gaskets and seals and distort the cylinder head , as well as cause cracks to appear in the cylinder block cooling jacket.

Fig. 1.1 View of tractor cooling system

Fig. 1.2. Schematic of tractor cooling system

Fig.1.3. Schematic of cooling system

1.Possible cooling system malfunctions:

• Low coolant level or insufficient fluid in the system.
• Faulty temperature sensor.
• Faulty temperature gauge.
• Piping failures- leaky fixings, mechanical damage and contamination.
• Faulty
• Centrifugal or water pump failure due to wear, belt or gear looseness, leak.
• Damage to blower control and drive such as: belt looseness in mechanical gear, damaged thermo relay, damaged electric motor, low hydraulic pressure in hydraulic drive, etc.
• Damaged or dirty radiator: leaking radiator, dirty radiator core or dirty outer surface.
• Radiator cap valve leak.
• Worn cylinder block and cylinder head gaskets and seals.
• Cracks in cylinder block and cylinder head cooling jacket

2. Causes of cooling system malfunctions

• Improper maintenance and operation of the tractor and the use of poor quality antifreeze, as well as its untimely replacement.
• Use of poor quality spare parts and consumables.
• Wear and tear of parts during operation.
• Poor system maintenance and repair.
• Significant contamination of cooling surfaces

Once you have familiar with the possible failures of the cooling system and their causes, you can proceed to the analysis phase.

STEP 2: ANALYSIS PHASE

Over the next two study hour, your group is in the classroom workshop as well as by the tractor to continue your research and analysis in a real-world setting by performing diagnostic tests on the engine’s COOLING SYSTEM, then analyzing the results and identifying the causes of the failure. Diagnostic tests: perform diagnostic tests following the instructions provided for the tractor engine cooling system. The teacher stands by your side, monitors your work and helps you with advice if needed. Initially, an external inspection of the machine for leaks and visible damage and inconsistencies to the engine and its components is started. The voltage across the engine coolant operating temperature sensors and the normal engine oil temperature should be measured with a Multimeter. The magnetic valve on the radiator cooling fin should also be measured. In this way, it is established whether the sensors are in working order. The temperature of the fluids is indicated by a sensor on the dashboard /measured with a heat temperature sensor/. In the course of the check, the degrees of coolant freezing are also checked with a Reflectometer. They are also monitored with the dashboard instruments located in the cabin. The appropriate working tools / wrenches, hex wrenches and other working tools / shall be used. Check the coolant level – look at the level in the expansion tank of the cooling system, there are two lines for the level- /Max. and Min./ The correct level of the fluid should be at a position between the two lines /Max and Min/. On some tractor models, the coolant level is checked by unscrewing the cap with the steam vent valve on the water radiator and looking at what the coolant level is inside the radiator. The level should be above the coil. Record results: Record all test results and compare them to normal readings and ranges.

Analysis of the causes: Based on the test results, you have made the following analysis of the possible causes of the failure. A large amount of plant debris was found accumulated in front of the cooling radiator. According to the students in this group – the strong wind has accumulated these residues in front of the radiator and they are one of the causes of the engine overheating. Other causes could be related to problems with the coolant, drive belt, thermostat, radiator, piping and radiator cap.

STEP 3: DECISION PHASE

In completing Step 3, you, the students are to propose decision to repair the damage based on your analysis, then prepare a list of tools and parts needed for the repair. The decision phase lasts for two study hour. In considering all the possible solutions to fix the fault, you, students have discussed and proposed the following::

• We found not good gear on the pump drive like play in the drive belt. It is not necessary to replace the belt, just to tighten it.
• Contaminated radiator outer surface – need to clean and purge with compressor.
• Radiator cap valve leak. In this case, the system pressure is low, and the fluid will boil even at idle. Fluid is discharged into the expansion tank when the engine is stopped. High antifreeze consumption is observed. To correct the problem the cap must be replaced.

LIST OF REQUIRED TOOLS AND PARTS Basic tools

• Wrench set – suitable sizes for the bolts and nuts connected to the cooling system and pump drive.
• Ratchet and bit set – for quick and easy removal and tightening of fasteners.
• Torque Wrench – for precise tightening of bolts, especially when a specific torque needs to be achieved.
• Pliers and screwdrivers – for working with clamps, hoses and other small fasteners of the cooling system.
• Belt tensioner (if available) – helps fine-tune belt tension.
• Caliper or ruler – to measure slack in the belt and set the correct tension.
• Manual purge pump – to remove air or impurities from the cooling system.

Specialized tools for belt work

• Torque Wrench – to accurately tighten tensioner bolts to prevent over- or under-tightening.
• Belt Gauge – measures the pressure or tension in the belt after tensioning to confirm that it is properly tensioned.
• Adjustable belt tension spring – to facilitate adjustment by maintaining constant tension during the adjustment process

 Equipment and machinery

• Air compressor – to blow out the cooling system, to clean components and remove dust.
• Cooling system vacuum tester – can help detect leaks or air pockets in the system.
• Belt tension gauge – to accurately measure belt tension and adjust to the correct level.
• Cooling system pressure tester – to test system pressure and detect potential problems that could cause overheating.
• Capacity container for collecting the coolant – for safe draining and storage of antifreeze when working on the system

Additional supplies and safety equipment

• Spare belts – in case the belt is too worn and cannot simply be tightened.
• Hoses and clamps for the cooling system – spare parts in case of need for replacement.
• Protective gloves and goggles – for safety when working with coolant and when handling the belt.
• Detergents – to remove deposits and dirt from the radiator and other components of the cooling system.
• Absorbent wipes – to clean up spilled coolant and keep the workplace clean

RESOURCES- LINKS

1. Tractor engine cooling system

https://www.kellradiatorservice.com/your-tractor-s-cooling-system-needs-attention-too/

https://www.youtube.com/watch?v=vRZu3-64yo0

https://www.youtube.com/watch?v=3XneH4sEmpE

https://www.platinumautoservice.com/coolant-system-flush

https://khetigaadi.com/blog/how-does-cooling-system-work-in-tractors/

2. Common tractor cooling system failures

https://www.fridayparts.com/blog/top-7-causes-of-tractor-cooling-system-overheating-failure?v=b&srsltid=AfmBOoobm7IswXXnbSpPGGcV6Tr9-3Wx5rbEAODab_7KQkEOg1XRsOWL

STEP 1 : LUBRICATION SYSTEM RESEARCH PHASE

During this phase, you, the students, will work in a study room where each of you has a personal computer/laptop and internet. The teacher will provide you with resources to complete this step in the form of technical information to familiarize you with the basic principles of operation and common problems and failures of the tractor system you are investigating. For basic information, you will use links on the Internet, the material from which is mostly in English. This information will also help you to complete the next two steps of the assignment. The research phase is two study hour. The purpose of the lubrication system is to lubricate the rubbing parts of the engine to reduce friction and delay wear in the engine, and also to cool the used oil and store the engine oil. The system consists of:

• Oil pump with receiver;
• Oil filter;
• Vent
• Oil radiator
• Piping

Fig. 2.1. Engine lubrication system

Fig. 2.2. Operation of the lubrication system

Fig. 2.3. Lubrication system of a diesel engine

1. Engine lubrication system faults

The faults that can occur in the lubrication system are extremely few, but their consequences cause very serious damage to the tractor. The following faults of this system can be distinguished:

• Oil pump wear or failure, oil pump seal failure.
• Clogged oil filter, poor oil filter retention.
• Oil pressure sensor failure. Pressure valve sticking, low oil level.
• Presence of coolant in oil.

The main causes of these malfunctions are:

• Violation of operating rules, unqualified maintenance and repair of the lubrication system;
• System components reaching their final operating date.

  External signs of a fault in the lubrication system are:

• Low oil pressure, increased oil consumption.
• Lubrication system malfunctions. Dashboard warning light alarms for reduced oil pressure. If the oil pressure drops, further operation of the tractor must be stopped.

STEP 2: ANALYSIS PHASE

Over the next two study hours, your group is in the Study Workshop, as well as at the tractor, to continue your investigation and analysis in a real-world setting, performing diagnostic tests on the LUBRICATION SYSTEM , then analyzing the results and identifying the causes of the failure. Diagnostic tests:

1. Check oil level when engine is not running – level is within acceptable limits
2. Check oil quality- colour, viscosity etc.- meet standard
3. Check for leaks on tractor engine. External leaks are accompanied by the appearance of a specific antifreeze smell, as well as dirt under the tractor and on the engine – no leaks

Recording the results During the checks carried out, the students found that the tractor engine lubrication system was in good working order. Analysis of the causes that can lead to failure of the tractor lubrication system   If there is increased oil pressure, the reason is that oil with a higher viscosity is used, there may be contamination of the pipes or a blockage of the radiator. Low oil pressure can be caused by an insufficient amount of oil, a worn or damaged oil pump, reduced viscosity of the oil due to its incorrect selection, water or other substances getting into the oil, as well as an increase in the clearances between the rubbing surfaces. Accelerated oil contamination is a criterion for a broken oil film, clogged oil filter or blocked relief valve. There are no known causes of failure in the tractor’s lubrication system.  

STEP 3: DECISION PHASE

When performing Step 3, the students do not propose solutions to repair the damage, because none have been found.

RESOURCES- LINKS

https://www.youtube.com/watch?v=r9czQz5dx68

https://www.gulfoilltd.com/blog/how-does-the-engine-lubrication-system-work

STEP 1 : RESEARCH PHASE OF THE FUEL SYSTEM

During this phase, you, the students, will work in a study room where each of you has a personal computer/laptop and internet. The teacher will provide you with resources to complete this step in the form of technical information to familiarize you with the basic principles of operation and common problems and failures of the tractor system you are investigating. For basic information, you will use links on the Internet, the material from which is mostly in English. This information will also help you to complete the next two steps of the assignment. The research phase is two study hour.

1. Damage to the fuel system of a diesel engine

Damage to the fuel system includes injection failure and failure of other structural elements of the system:

• The most serious malfunction is a leak in the system, which, in addition to economic losses, poses a threat to the fire safety of the tractor.
• Reduced fuel pump performance, clogged fuel filter.
• Clogging of the fuel supply
• System leaks, water in the fuel.

The main cause of these malfunctions is a violation of the tractor’s operating rules. Fig. 3.1. Diesel fuel system diagram.

STEP 2: ANALYSIS PHASE

For the next two study hours, your group is in the workshop as well as at the tractor to continue their research and analysis in a real-world setting by performing diagnostic tests on the tractor’s FUEL SYSTEM, then analyzing the results and identifying the causes of the failure. Diagnostic tests: The malfunction of the fuel system can be diagnosed by external signs. Such signs are:

• Interruptions in engine operation and increased fuel consumption.
• The presence of the smell of diesel fuel (petroleum).
• Fuel stains – this indicates a leak in the system.
• Difficulty starting the engine or not starting at all
• Unstable engine idle.
• Engine power reduction.
• Malfunction of fuel injectors

During engine operation, the fuel system is contaminated not only by solid particles, but also by resins and fuel components. The injection nozzles work in conditions of high temperature around 100-120⁰ C and high injection pressure – from /8 – 22 bar/ and they appear as the most vulnerable element to contamination. The use of low-quality fuels worsens the performance of the engine and puts a strain on it. A dirty nozzle reduces performance and the injection into the cylinders takes place in an incorrect way – incomplete combustion of fuel, increase in fuel consumption, etc. Engine performance becomes uneven, engine loses power, unstable idling, increased exhaust emissions, etc. Injector Performance Diagnostics – After diagnostics have been performed, the injectors need to be removed from the engine and placed on a diesel fuel diagnostic bench to check their operation, performance and “dusting”. In case of detection of poor quality operation of the nozzles, they are washed with a special fluid in a bath and with Ultrasound. The cleaning fluid bombards the cleaning element and breaks off /removes/ the dirt. The nozzles are then placed back on the diagnostic bench to check their operation Analysis of causes All possible, major causes of failure in the tractor’s fuel system, such as poor quality fuel, prolonged engine idling, high engine rpm or under high loads, are rejected by the students as reasons why the tractor engine cannot to catch fire. A slight fuel leak was detected at one of the low pressure fuel lines. The group of students investigating the fuel system of the tractor came to the conclusion: The damage in the fuel system of the tractor was due to the strong impact of the tractor on the concrete element of the irrigation system in the field, which caused displacement of the low pressure fuel lines. As a result of this displacement, air entered the fuel system, which impeded the normal supply of fuel to the fuel Injection Pump and the Fuel Supply pump.

STEP 3: DECISION PHASE

In doing Step 3, you students should propose solutions for repairing the damage based on the analysis done, then prepare a list of the necessary tools and parts for the repair. You have two study hours. The solutions that the students suggest to be taken to remedy the damage are the following:

• Replacement of the low pressure fuel pipeline with a new one.
• Bleeding the fuel system

LIST OF REQUIRED TOOLS AND PARTS  Basic tools

• Wrenches (metric and inch) – for loosening and tightening various bolts and nuts on the fuel system.
• Ratchet and bits – a handy tool for working in tight spaces with different sized bolts.
• Screwdrivers – for opening covers and removing brackets.
• Air compressor – to purge the system of impurities and maintain pressure if necessary.
• Hoses and fittings – to connect to the fuel system when bleeding is performed.
• Pressure gauge – to measure the pressure in the fuel system and ensure the correct pressure during bleeding.
• Specialized Bleeding Tool (If Available)

Machinery and equipment

• Diesel pressure pump – to create pressure in the fuel system during bleeding.
• Vacuum pump – when needed to create a vacuum to remove air from the system.
• Diagnostic system for fuel systems – to check the condition of the system and the presence of errors.
• Measuring bench for fuel pumps and injectors – if additional testing of fuel system components is required.
• Fuel container – to collect fuel when air is removed if a system drain is performed.
• Workbench with vise – to fix components if disassembly and inspection is required.

Consumables and safety

• Fuel hoses – spare hoses if replacement is required.
• Fuel filter – new filters when replacement is needed.
• Rubber gloves and protective glasses – for operator safety when working with fuel systems.
• Absorbent towels – for cleaning spilled fuel

RESOURCES- LINKS

„Bleeding the Fuel System“ – John Deere and others

https://www.youtube.com/shorts/3eEGMIv09nY

https://www.youtube.com/watch?v=cIkMtnd3LGQ

  WEBQUEST RESOURCES – TRACTOR REPAIR Theoretically and practically, in recent years, in the development of WebQuest, resources are considered together with processes because they are interrelated. Below is a summary list of resources. This expanded description will help students navigate the tractor diagnostic and repair process while providing them with the resources and support they need.

1. Articles and manuals for tractor repair: Detailed written instructions and manuals that describe how to diagnose and fix various types of damage. Part of these materials are in paper form in Bulgarian and Russian, and another part in electronic form – THE LIBRARY OF THE PROFESSIONAL SCHOOL.
2. Repair Instructional Videos: Video tutorials that show step-by-step diagnostic and repair processes. They are useful for visual understanding of methods and techniques. They are presented in links to the texts on the PROCESS slide.
3. Tractor diagrams and schematics: Technical drawings and schematics that show the various components of the tractor and their relative arrangement. They are useful for understanding the structure and functioning of systems. They are presented in links to the texts on the PROCESS slide.
4. List of necessary tools and parts – the texts on the PROCESS slide are presented.

The next day, the teacher organizes a rubric to evaluate the completed task, within one hour, in the classroom, choosing the combined approach evaluation. In this approach, both the collective work and cooperation of each of the groups, as well as the individual contribution of each student, will be evaluated.

The teacher has developed clear and specific assessment criteria to be used by the students.

The names of the student who performed the assessment are removed and replaced with numbers or codes. Each student receives a table with the evaluation criteria. In the Evaluation Sheet, the student can also self-assess   – this option is recommended, but not mandatory.

After all the Evaluation Sheet have been ready, the teacher can organize a class discussion about the grading process where the students share their observations and discuss what they have learned. The final decision on the evaluation of the work is made by the teacher. The teacher reviews the grades and feedback provided by the students to ensure that they are objective and reflect the set criteria. The teacher may also correct some grades if he considers them to be unreasonably high or low.

The criteria for evaluating each student are as follows

1.1. UNDERSTANDING THE TASK

• 4 points – The student demonstrates an accurate understanding of the task.
• 3 points – The student understands the task, but uses a limited number of sources of information.
• 2 points – The student includes materials that are not directly related to the topic; one source is used. The information collected is not analyzed or evaluated.
• 1 point – The content of the task is incomprehensible to the student. Searching for information on the Internet is difficult.

1.2. KNOWLEDGE

• 4 points – Presentation of acquired knowledge clearly, systematically and correctly. Using the right and relevant information from various highly reliable sources with successful adaptation to the topic.
• 3 points – Presentation of a large part of the knowledge acquired during the work clearly and comprehensibly. Selecting relevant information from reliable sources.
• 2 points – Presentation of a relatively small part of acquired knowledge.Selecting information from sources that are not too clear and adapting some of it to the topic.
• 1 point – Selecting information that is not very relevant from obscure sources. Insufficient knowledge presented, unclear without substantial meaning

1.3. TECHNICAL VOCABULARY

• 4 points – Technical vocabulary used by the student in an exemplary manner. Correct understanding of the special terms used.
• 3 points – Correct use of technical terms by the student. Minimal errors.
• 2 points – Uses technical vocabulary in a limited and often inadequate way. Common mistakes.
• 1 point- Inadequate use of technical terms, lack of specialized vocabulary or major errors

1.4. CREATIVITY AND ORIGINALITY

• 4 points – The student shows original thinking and an innovative approach.
• 3 points – Standard ideas that are properly presented.
• 2 points – Little creativity, mainly following established patterns.
• 1 point – Lack of creativity, repetition of other people’s ideas without original contribution.

1.5. COOPERATION AND TEAMWORK

• 4 points – The student actively cooperates and supports his classmates.
• 3 points – Good cooperation with minimal communication problems.
• 2 points – Limited cooperation, visible difficulties in teamwork.
• 1 points – Lack of cooperation, teamwork is ineffective

1.6. PROMOTION OF RESULTS

• 4 points – The student shows original thinking and an innovative approach to preparing a project presentation. Participates in the preparation of a presentation
• 3 points – The student has standard ideas for preparing a presentation of the project, which are appropriately presented. Participates in the preparation of a presentation
• 2 points – The student was only involved in developing the structure of the presentation.
• 1 point – The student did not participate in preparing a presentation of the project.

EVALUATION SHEET

Each Evaluation Sheet has a two-digit number – the first digit is the group number – from 1 to 3, the second number is the student’s name – from 1 to 3.

Evaluation Sheet of a student with code 1.1

Final grades for each student