When it comes to mechanical problems It is necessary to what?
to evaluate whether the mechanical problem will cause an accident or breakdown versus the need to get the load moved.
How can you minimize deadline situations?
By listening to the driver and technician and making decisions based on the given facts and possible consequences.
Who should perform pre-trip inspection and where should it start?
The driver should perform a pre-trip inspection. The inspection should start at the left front of the vehicle and work in a counterclockwise direction around it.
How valuable are permanent records?
Are invaluable from a performance standpoint. A study of failures of individual components can alert the manager of the need to take corrective action. It also highlight components the have performed satisfactorily.
Where should any repair procedures be noted?
Must be noted using a sign-off sheet before the vehicle is put back into Service. If the problem noted did not require repair, but was still looked at, then this must be recorded as well. A copy of the inspection report must remain with the vehicle.
What should be included in service logs and why are they important?
Should affect work performed on a vehicle. Active complaints/problems should always be addresses immediately with quick visual inspection to determine if the repair can be made quickly and easily. The check the vehicle records if it appears that quick repair cannot be made. All information that can be obtained could be invaluable to the timely repair the vehicle.
Federal Motor Carrier safety Regulations
Part 393, States that anything mechanical component that can either cause or prevent an accident is a safety item. All vehicle safety problems should be addressed, no matter how minor they appear. Section 396.19, States it is the fleets manager’s responsibility to ensure that all personnel doing annual inspections are qualified to preform those inspections. They should understand the inspection criteria and be able to identify defective components and systems.
Federal Highway Administration
Has set up a minimum inspection standards program, under which each vehicle must carry proof that an inspection was completed. Proof can either be copy of the inspection form kept on the vehicle or a decal. If using decal , a copy of the inspection form must be kept on file and should indicate where an inspector can get a copy of it. The only requirement of a decal itself is that it be legible. Each vehicle must be inspected separately. This means a tractor/trailer is considered to be two vehicles, each requiring a decal; a converter dolly is separate vehicle. The decal must show the following information: date vehicle passed inspection, name and address to contact concerning inspection record, and VIN.
Regulation
Places a greater emphasis on the post-trip inspection, most operators agree the pre-trip inspection in more important. Because the driver is doing the inspection will be operating that particular vehicle, the incentive to ensure that the vehicle is safe is probably greater. Repairs are cheaper and less time-consuming if the driver finds them on the pre-trip before inspectors levy fines or impose penalties.
Today’s Diesel trucks contain
A verity of computerized control systems to operate engines. transmissions, antilock brakes, etc. According to Society of automotive engineers(SAE) Standard J1930, diagnostic codes are known as diagnostic trouble codes (DTCs). DTC access may be by blink codes or read off the chassis data-bus. You need to understand how to check, record, and clear DTCs.
At what RPM should engine should crank?
Electronic diesel and gasoline-fueled engines will not inject fuel until at least 150 rpm.
And Using ether can cause detonation (Loud hammering sound). It should never be used on glow plug applications.
What are the Exhaust smoke colors?
White smoke is an Indication of unburned fuel exiting the exhaust pipe. Blue smoke is an in dictation of burning oil. Black smoke is caused by air starvation or rich-fuel mixture.
Governed RPM
The Maximum engine RPM that an engine is rated for and the fuel or engine-management system will attempt to limit speeds above that setting.
Vibration Damper
Mounted on the front of the engine, balancing harmonic vibrations caused by torsional loads of the rotating crankshaft.
All accessory belts
Should be checked for obvious signs of wear, tension, and/ or correct application(if suspected). A belt tension gauge should be used whenever possible for most accurate readings. If one is not available, Then the normal deflection points at the specified locations and measurements should be observed. an idler hub should be checked for loos or worn bearing, condition of belt surfaces, cracks from fatigue of deterioration, and the correct application.
What two types of leaks should an engine be checked for while doing an inspection?
Static (while it’s running) and Dynamic (while it’s off) Leaks
What is mandatory, when checking for fuel leaks on an engine?
It is mandatory that the engine is running, thus making the leak very apparent.
Why is a fuel leak more hazardous while the engine is running?
Due to the higher fuel pressure.
What should inspection of the cooling system include?
A check of the: cooling system maintenance history coolant change intervals component replacement (s) past diagnosis
Although a leak in the cooling system a serious problem, why is it not the criteria for deadlining?
It is not safety-related.
What is the most effective way of diagnosing a vehicle with defective engine mounts?
Observe the engine mounts while torquing the engine with the brakes applied. This will allow a broken or deteriorated engine mount to be quickly observed and noted for replacement.
Why is checking the engine oil level a critical part of a PMI?
The correct oil level is essential for proper engine lubrication and cooling.
What are the effects of an oil level too low?
Oil level too low may allow air to be drawn into the pump and a loss of oil circulation.
What are the effects of an oil level too high?
Oil level too high may allow the oil to be whipped by the crankshaft, which could cause oil aeration.
What does aerated oil do?
It is not compressible and does not provide a continuous flow of oil to the various components that depend upon oil for lubrication, cooling, or hydraulic operation, which could result in engine failure or accelerated wear..
What is the recommended procedure for checking the oil level?
Be sure that the vehicle is on level ground and has not been operating for at least five minutes. Remove the dipstick and wipe with a clean rag to remove any oil from the previous operation. Fully insert the clean dipstick and remove to obtain the correct reading.
Why is it careful examination of the wiring harnesses essential?
Many systems on a modern truck depend upon the electrical circuit in one way or another.
What is the procedure for checking wiring harnesses?
- Pay particular attention to any areas where the wiring harness contacts anything metal.
- Wiring harnesses should be covered with protective armor and secured in place with brackets and loom holders.
3, Make sure all wiring is properly routed to avoid damage from moving parts and hot exhaust manifolds
Why are connectors constructed with waterproof seals?
To prevent corrosion.
Why should seals on connectors always be in good condition?
Many electrical problems are traced to problems at the connectors.
What should you do to remove a wire from a connector for repair or placement?
Be sure to use the proper tools and replacement parts. Wherever a splice or repair is made to the wiring, it should be sealed to weatherproof it
What should you look for when checking fuel tanks during a PMI?
- Signs of leakage at any point, with special attention to all seams and any damaged areas.
- The fuel tank mounts should be attached to the frame and the tank should be free from any cracks, corrosion, and damage that could cause failure.
- There should be no sign of tank shifting and all mounting bolts should be in place and tight.
- Check the tank fuel supply for moisture contamination by the use of a rod or probe coated with water detection paste, which is designed to change color when it comes in contact with water.
- If more than the tip changes color, the tanks may require draining to remove the water.
- Water in the fuel tank can be drained by the use of a suction pump with a long sump that reaches to the bottom of the tank where the water would accumulate, or by a tank drained.
What should you look for when checking the fuel tank cap during a PMI?
- The fuel tank cap should be easily installed and removed and should be able to provide a good seal.
- Check to ensure that the cap seal is in place and in good condition.
The fuel lines, including the crossover line, must be leak-free and should be secured by loom or brackets.
Inspect all routing to ensure that no line damage will occur due to contact with other objects.
If the line is chafed but no leak is present, a replacement decision should be made on the severity or probability of a future leak or breakdown.
What should you do when inspecting a water separator/fuel heater during a PMI?
- Routine water draining and changing the filter element when the other engine filters are changed is a good practice.
- The aftermarket filter element that has a longer service life, should be changed at specified intervals.
3,. Fuel contamination can occur easily if the canister is primed with unfiltered fuel or dirt is allowed to enter when the element is being changed.
The filters must be primed before the engine can be started.
Why do some manufacturers recommend that the secondary filter be installed dry and primed with a hand pump?
To ensure that only filtered diesel fuel enters the secondary filter.
How would you ensure that no air bubbles are present at the fitting?
A line fitting upstream from the pump should be cracked open and priming should continue until no air bubbles are present
What is the procedure for inspecting the crankcase ventilation system during a PMI?
- The PV valve should always be checked when any inspection of the emission control system.
What does improper operation of the PCV cause?
Erratic engine operation as well as higher than normal gasoline exhaust emissions, causing fines and penalties due to violations.
How should you check exhaust system mountings for looseness and damage?
- Use a pry bar to check exhaust pipes and support brackets for looseness.
- All mounting brackets should be examined for cracks and clamps must be tight.
- The complete system should be visually inspected for rust, damage, and cracks.
What happens when an exhaust system is leaking in front of below the driver/sleeper compartment and the floor plan has potential for cab entry of exhaust fumes?
The fumes can result in a drowsy o asphyxiated driver, which could cause an accident.
How should the exhaust routing be checked and assembled?
The exhaust routing must be checked and assembled in a way that does not allow contact of the exhaust system with any wiring, air lines, fuel lines, or combustible materials.
The Commercial Vehicle Safety Alliance (CVSA) our-of-service criteria would deadline a vehicle for any of these faults.
What depends on whether the truck air induction ducts need to be cleaned on every PMI?
The conditions the vehicle is driven in.
What should you do, concerning the truck air induction systems during a PMI?
- Give a full visual inspection to the air induction for blockage and/or deterioration.
- The air inlet restriction should be checked with a water manometer or accurate vacuum gauge.
- If the restriction exceeds the maximum specifications, the air filter should be checked.
What will tapping on the floor or blowing with air pressure to dislodge dirt do to restricted dry filters?
It will result in filter damage and dirt bypassing the filter if it is reinstalled.
How does a turbocharger operate?
A turbocharger operates on the principle of thermal expansion to drive a turbine wheel, located in the turbine housing.
This, in turn, spins the compressor wheel in the impeller housing.
Where is the compressor wheel located and what does it do?
The compressor wheel is located in the inlet side and draws in fresh air and pressurizes it.
Where is it necessary to contain the pressurized air?
It necessary to contain the pressurized air in hoses, manifolds, and an intercooler.
A turbocharger can operate within manufacturer’s specifications and still have acceptable leakage. True or False?
True
How would you test for proper leak rate?
Follow the most current information provided in the manufacturers’ service bulletins and do not exceed the recommended test air pressure.
How should clamps be torqued?
The clamps used are spring-loaded and should be torqued to specifications and placed in a way as to not chafe through other hoses or components with engine movement.
At what speed can modern diesel engine turbochargers perform?
Modern diesel engine turbochargers perform at very high speeds and can reach well over 100,000 rpm.
What should you do when running the engine without the air intake?
Be sure to install an intake guard over the turbocharger inlet.
How much air by volume do engines require?
- Engines require approximately 9,000 to 10,000 gallons of air by volume for every gallon of fuel consumed.
- This results in a volumetric air-fuel ratio of approximately 10,000to 1 for both gasoline and diesel engines.
What is the stoichiometric ratio?
Air fuel ratio by mass of approximately 15:1
What is dusting; what causes it; How can it be prevented??
When a large volume of air enters an engine, it is important to provide good filtration, as airborne dust, sand, and other debris ingested into the cylinders will lead to premature engine failure called “dusting” caused by loose clamps or ill-fitting air filter assemblies.
What causes a rich fuel condition and causes a cylinder wash down of the oil film on the cylinder walls?
Obstructions such as restricted air filter will reduce airflow/volume and cause an engine to operate in a rich fuel condition, and cause cylinder wash down of the oil film on the cylinder walls, leading to engine failure.
What are typical restriction specifications for naturally aspirated and boosted engines?
Typical restriction specificationsare15inches of water vacuum for naturally aspirated engines and 25 inches of water vacuum for boosted engines.
What is EGR?
EGR is a method of reducing oxides of Nitrogen (NOx) by circulating a small amount of exhaust gases back through the intake manifold to dilute the intake charge and lower the combustion temperature.
On what should the EGR function?
The EGR should only function on a warm engine, operating above idle.
Whatis a common test of vacuum-operated EGR valve?
Apply vacuum to the valves diaphragm at idle, which should produce a rough idle or even stall out. At above idle operation should be present at the valve.
What is an Air Inlet Temperature Control?
Air Inlet Temperature Control is simply a dual position door located in the air when the engine is cold. The preheated air is air drawn past the exhaust manifolds through ducting and shrouds.
What is EFE?
EFE is a process of diverting exhaust gases through a passage in the intake manifold during cold engine operation, to prevent fuel condensation on the cold walls.
How do some EFE systems use to warm the intake?
An electric heating grid
What do EVAP Systems to warm the intake?
A sealed fuel tank with pressure relief vents that are plumbed to a carbon canister. The carbon canister absorbs the carbon from the gasoline vapor. When the engine is running, manifold vacuum draws the gasoline vapor into the engine to be burned.
What is the function of Catalytic converters?
Catalytic converters use catalyst substances to convert harmful emissions into non-harmful emissions.
Which substances are oxidation catalysts that oxidize hydrocarbons and carbon monoxide into water and carbon dioxide?
Palladium and platinum
Which substance is a reduction catalyst that tries to reduce oxides of nitrogen into the elements nitrogen and oxygen?
Rhodium
How do computer-controlled types of diesels meet emissions standards?
Computer control types of diesels have very precise control over the combustion process.
How are diesel engines being equipped to meet more stringent emission standards?
They are being equipped with C-EGR -Cooled-exhaust gas re-circulation.
What do some engines use to reduce cold engine emissions?
To reduce cold engine emissions, some engines use intake air heaters to reduce unburned hydrocarbons.
What are the different fan clutch types?
Viscous, thermatic, air supply, air release, electric, and hydraulic.
What should viscous and hydraulic units NOT exhibit?
Viscous and hydraulic units should not exhibit any signs of fluid leakage.
What are most pneumatic fan clutch failures caused by?
Air leaks
What engages fan clutches?
Fan clutches may be engaged by engine compartment temperatures, fluid temperatures, or by management strategies.
What happens when the fan receives road debris created by the ram air effect of road speed and the vacuum of the fan rotation?
- This suspended particulate travels through the radiator and impacts the fan blades causing a sandblast effect on the fan blades, clutch, and related components assemblies.
- Riveted fan blades can loosen.
- Plastic fan blades can be weakened and crack.
- Fan clutches can become inoperative.
Why should you check fan blades before running the engine?
Fan blades can dislodge while performing inspections.
Why should you inspect for weak or broken engine/transmission mounts?
They can lead to fan blade and shroud damage.
For fan efficiency, while performing preliminary tests, what should you check?
Check for proper blade clearance, alignment, engagement, and engine/transmission mount function.
Also, shroud clearance and flow restriction may affect fan efficiency.
Why are radiators susceptible to damage from airborne objects
Because of their location, mostly at the front of the vehicle.
What types of damage or restriction can radiators have?
bent cooling fans, corrosion, or in the event of large objects, punctures causing loss of coolant.
Why is it important to inspect the cushion mounts at service intervals
To prevent vibration ad other movement damage of the radiator and related components.
What other components are mounted close to the radiator?
The engine, with the intercooler, the air conditioner (A?C condenser, and oil coolers inhibiting airflow to it.
What should you do to avoid the severe compromise of the radiator’s ability to effectively cool, during service intervals?
Separate the radiator from these units: engine, with the intercooler, the air conditioner (A/C condenser and oil coolers and inspect for buildup of compacted road denis that can severely compromise the radiator’s ability to effectively cool and rinse out with low-pressure water.
What is the normal system pressure range for a cooling system?
The normal system pressure range for a cooling system is in the range of 15 pounds per square inch (psi), depending on the particular design of the vehicle being tested.
What is the purpose of the radiator cap and why should you test it?`
- The purpose of the radiator cap is to allow a higher operating temperature of the engine by raising the boiling point of the coolant (3 degrees for 1 psi).
- It is important to test the radiator cap to ensure that it will retain the indicated pressure reading.
How do you test the radiator cap?
- Using a pressure tester unit, install the cap onto the tester and proceed to apply pressure to the specified pressure release point.
- An underperforming cap may cause engine overheating and coolant loss.
How many seals should the coolant system have if it has a recovery tank and what is the purpose of the seals?
- If the coolant system has a recovery tank, it has two seals.
- The one on the end of the coil spring is to contain fluid and the rubber seal under the cap lid is to create a vacuum and aid in the returning coolant from the overflow container to the engine.
In doing a visual inspection of the entire cooling system, what should you look for?
- All heater and water hoses should be sound and pliable.
2. All clamps should be checked for tightness and/or deterioration.
How should you inspect hoses?
Hoses should be checked by looking inside the hose for cracks and splits because hoses deteriorate on the inside before any wear occurs on the outside.
How are silicone hoses easily damaged?
over tightening the clamps.
How should you inspect silicone hoses?
- Silicone hoses require special clamps that should be torqued carefully.
- When correctly installed, they provide better sealing and longer service life.
- Some coolant leaks occur only when the system is cold.
- They are sealed by expansion during operating temperatures.
- So check for leaks both when cold and at operating temperature.
What does the radiator cap do?
The radiator cap will maintain the pressure within the cooling system at or below approximately 15 psi.
What happens to the radiator cap during heavy loads and prolonged periods of idling?
During heavy loads and prolonged periods of idling, pressure may exceed the rating of the radiator cap and fluid will be vented to an expansion tank or bottle.
What happens when enough fluid has been vented to reduce the pressure within limits?
Once enough fluid has been vented to reduce the pressure within limits, the spring tension of the radiator cap will close the vent line.
What does a constant overflowing of the fluid from the tube indicate?
A constant overflowing of the fluid from the tube may indicate air pockets, uneven heating, or hot spots in the engine.
What do repetitious and rhythmic surges in the level usually indicate?
Repetitious and rhythmic surges in this level usually indicate a leak to the combustion cylinder, such as a blown head gasket.
What do you use to test coolant freeze ad boil protection levels?
Coolant freeze ad boil protection levels are tested by a hydrometer or refractor.
What is required to raise or lower the protection level?
Different antifreeze to water ratios are required, depending upon the temperatures the vehicle will encounter.
What is the most common antifreeze to water ratio?
A 50/50 mixture is most common.
To be compatible with the different gaskets and metals that are in various engines, what do current trucks use?
Current trucks use one of three types of antifreeze that may be identified by a label in the engine compartment: ethylene glycol, propylene glycol, or carboxylate, which is-life antifreeze.
What do Original Equipment manufacturers (OEMs) recommend in regard to testing for the type of antifreeze used?
OEMs recommend that the coolant SCA level be tested at each oil change interval.
If there is a substantial loss of coolant and the system has to be replenished, what should be done?
The SCAs should be tested.
What are SCAs?
Supplemental coolant additives
What does OEM stand for?
Original equipment manufacturers
What does each test provided by the OEM designed for?
Each test provided by the OEM is designed to monitor the SCA package required for its product and can not generally be used for other OEM’s product.
What do coolant test kits permit the technician to do
Coolant test kits permit the technician to test for appropriate SCA concentration, the pH level, and the total dissolved solids (TDS)
What does TDS stand for?
Total dissolved solids
What does pH level determine in the coolant?
The pH level determines the relative acidity or alkalinity of the coolant.
What do acids in the coolant do?
Acids may form in engine coolant exposed to combustion gases or in some cases when cooling system metals (ferrous and copper bases) degrade.
Explain the pH test for coolants.
The pH test is a litmus test in which a test strip is first inserted into a sample of the coolant, then removed and the color of the test strip indexed to a color chart between 7.5 and 11.0 on the pH scale.
What are higher acidity readings and what do they indicate?
Higher acidity readings are readings below 7.5 on the pH scale and are indications of corrosion of ferrous and copper metals, coolant exposure to combustion gases and in some cases, coolant degradation.
What does higher than normal alkalinity readings indicate?
Higher than normal alkalinity readings indicate aluminum corrosion and possibly that a low silicate antifreeze is being used where a high silicate is required.
Why is it important that coolant filters have service intervals and manufacturers’ literature consulted?
To determine the proper maintenance schedule. On diesel engines, coolant filters become restricted and coolant additives break down due to extended operation.
Not complying with this service information will result in premature engine failure.
What precautions should you take if coolant filters contain an SCA charge and corrosion inhibitors?
The filters should only be replaced as directed; never over-service coolant filters that contain an SCA charge.
What does the SCA package recommended by an engine manufacturer depend on?
Whether wet or dry cylinders are used, the materials used in the cooling system components, and the fluid dynamics (high flow/low flow) within the cooling system.
The operator may wish to adjust the SCA package to suit a specific operating environment or set of conditions. What would abnormally hard water require?
Greater anti-scale protection
What do most OEMs suggest when it comes to testing
SCA levels and addiding SCA?
Most OEMs suggest testing the SCA levels in the coolant followed by adding SCA to adjust to the required values.,
What should you never dump into the cooling system at each PMI?
Unmeasured quantities of SCA into the cooling system at each PMI.
What does cooling system maintenance require, and what is important to know about coolants?
Cooling system maintenance requires periodic draining and refilling of the system, and when doing this, it is important to know that all coolants are alike, and are not compatible with each other.
What is the difference between the different types of coolants?
Extended Life Coolants (ELCs) have a longer service life than Ethylene Glycol (EG) and Propylene Glycol (PG) coolants.
Why id it necessary to bleed the system when refilling the coolant system?
To allow trapped air to escape.
How do you bleed the system when refilling the coolant?
Bleeding the system can be done by opening a hose or fitting on top of the engine before the thermostat and filling the system until liquid coolant appears. This prevents trapped air from creating a hot spot when the engine is first started.
How should drained coolant be handled?
Drained coolant should be handled in accordance with federal, state, and local regulations, including on-site recycling or removal by a licensed service.
What should be posted in your work area concerning the proper handling of each coolant used?
A material safety data sheet (MSDS)
Where and how is the water pump mounted?
The water pump is usually mounted on the front of the engine block with a gasket between the block and the water pump.
A leaking water pump causes coolant to drip from the drain hole on the bottom side of the pump. What does coolant leaking past the water pump seal lead to?
Coolant leaking past the water pump can lead to bearing failure,
How would you know if there is a defective water pump bearing?
A defective water pump bearing may cause a growling noise with the engine idling.
After the initial lube change of 1,000 to 3,000 miles, when should subsequent lube changes be made>
At the engine manufacturer’s suggested intervals for the oil type used, dependent on Class A or AA highway operation.
What defines Class A operation?
Class A operation is defined as driving on well-maintained highways of concrete or asphalt.
What do oil filters do>
Oil filters trap particles that would otherwise cause damage to critical components like engine bearings.
What materials do modern engines use for the housing and for machined parts and what type of inspection should the technician use?
Modern engines use a variety of materials from cast iron to die-cast aluminum for the housing; and steel or plastic for machined parts. The technician should use a visual inspection of filter assembly parts.
What can cracks in the housing cause?
Major engine failure.
What do some filter assemblies incorporate in their housing and how should these be handled in the PMI?
Some filter assemblies incorporate a bypass valve in the housing. These valve assemblies must be removed and inspected for corrosion, wear, and other signs of damage during overhaul or any time the filter assembly contains metal particles.
How should you inspect canister filters?
Canister filters should be cut open and the element material examined for content; suspended metal particles indicate the potential for bearing failure.
What does a milky gray sludge indicate?
Water in the oil, caused by a possible head or cylinder block leak, which may already have caused bearing damage.
What would result if all gasket surfaces are not straight and free of nicks?
This could cause an improper seal of assembly.
On element type filter assemblies, what should be in good shape?
Ensure that housing grooves, center bolt threads, springs, metal gaskets, and spacers are in good condition.
After you have inspected for distortions in the canister, cracks around the cannister bolt hole and clogged passageways in the bolt, what should you do?
- Reinstall the bypass valve according to the manufacturer’s installation procedures and set for proper pressure.
- Replace the element and all gaskets and supplies seals.
What should you do when reassembling filter assemblies?
Apply a small amount of oil to all seals to ensure a tight seal.
Why is the pre-filling of canister type filters recommended by most OEMs?
To ensure adequate oil is present during startup to lubricate the bearings.
Used oil and filters are considered ________________ and must be disposed of in accordanc with federal, state, and local regulations.
Hazardous waste.
What precautions should you use with used oil?
Used oil can harmful to your skin and you should take steps to minimize contact with it.
Why is an engine oil sample taken during a normal PMI?
For inspection of contamination, metal, and dirt content; also corrosion-causing agents such as sulfuric and hydrochloric acids and some esters..
Why is the engine oil sample to be taken at normal operating temperature?
To ensure that all possible contaminants and corrosives are measure in the oil in its normal operating condition.
When should the oil sample be taken?
During the oil change at the midpoint of the drainage.
How can low-level testing be done?
In the shop with a blotter test kit. This kit will compare the darkness and fluidity of a drop of oil on the blotter paper to a code chart that identifies the level of dirt, soot, and particles found in the oil, and the color change of the oil will indicate the acidity.
What does the more comprehensive test performed in a lab show?
These labs perform spectrographic tests. which identifies and quantifies the contaminants found in the oil.
