Maintenance and repair methods of loader forklift (2)

Mar 05, 2023

1. What are the reasons for the "boiling" of the loader forklift diesel engine? How to rule out and prevent?

"Boiling" refers to the phenomenon that the temperature of the diesel engine is too high, and the coolant boils and steams in the water tank. The main reasons for the "boiling" of the diesel engine and the prevention and elimination methods are as follows:

(1) The inner wall of the heat dissipation pipe (core) of the radiator is too thick, which affects heat dissipation. During use, clean cooling water should be added; and the scale in the water tank should be removed regularly;

2. Radiator or cooling system leaks, resulting in insufficient coolant. Check the cause of water leakage, and add enough cooling water after troubleshooting;

3. The cylinder head gasket or cylinder liner is damaged, and the high-pressure gas in the cylinder enters the water cooling system, causing the water tank to "foam" and "boil" (in this case, it is often accompanied by the emulsification of diesel engine oil). Check whether the cylinder gasket or cylinder liner is damaged, and replace it if necessary;

(iv. The water pump is damaged, the cooling water does not circulate or the circulation intensity is insufficient. The cause of the damage to the water pump should be checked, and a new water pump should be replaced if necessary;

(5) The machine works under high load for a long time, the fan belt is too loose, and the wind speed is not strong, and the pot may boil due to overheating. The workload of the loader should be arranged reasonably to prevent the machine from overheating.

(vi) The thermostat is damaged, causing the large cycle to fail to open, causing the machine to overheat, and the thermostat should be replaced.

It should be noted that the loader working in the alpine region will also be boiled. The main reason is that the radiator freezes and the coolant cannot be circulated. Therefore, when using a loader in an alpine region, attention should be paid to adding a heat preservation device to the front end of the radiator.

1. What are the reasons for the "boiling" of the loader forklift diesel engine? How to rule out and prevent?

2. Radiator or cooling system leaks, resulting in insufficient coolant. Check the cause of water leakage, and add enough cooling water after troubleshooting;

(vi) The thermostat is damaged, causing the large cycle to fail to open, causing the machine to overheat, and the thermostat should be replaced.

3. The reason and elimination method of white smoke from the exhaust pipe of the loader forklift?

There is water in the diesel oil or in the cylinder liner, and the hydration turns into steam and is discharged from the exhaust pipe, that is, white smoke is emitted.

The main causes of white smoke from diesel engines and how to eliminate them are:

(1) Diesel is mixed with water, you should check whether there is water in the diesel;

(2) Improper adjustment of fuel supply advance angle

When the fuel supply advance angle is too small and the temperature of the diesel engine is not high, a part of the fuel will be discharged with the exhaust gas before it can be burned, and the discharged oil mist will form a white gas. When the heat engine is heavily loaded, the temperature of the combustion chamber and the exhaust pipe rises, and the diesel that cannot be completely combusted in the combustion chamber continues to decompose in the exhaust pipe, forming black smoke and being discharged. Check whether the oil supply time is appropriate.

(iii) Poor atomization of the injector

If the fuel injector is not well sealed, the atomization is poor, or there is even oil dripping, the oil entering the cylinder will not have time to mix and burn, and white smoke will be emitted. If the fuel injector drips heavily or multiple fuel injectors drip oil, the diesel will also escape into the oil pan and dilute the engine oil. Inspect the fuel injector and replace the needle valve assembly if necessary.

(iv) Cylinder liner water intake

The cylinder gasket is damaged, which connects the water channel or the cylinder liner crack, so that the cooling water continuously infiltrates into the cylinder. When exhausting, the discharged hot air evaporates or scatters, forming water mist or water vapor, which is discharged as white smoke. At this time, if white paper is placed on the exhaust pipe, it will be sprayed with small water droplets. The cause of the leak should be checked.

It should be noted that when the diesel engine is running cold, the exhaust pipe emits white smoke continuously. This phenomenon is more common when diesel engines are used in cold winter. This is because the temperature in the cylinder of the diesel engine is low, and the oil vapor on the cylinder wall evaporates and is discharged through the exhaust pipe, and the exhaust pipe also discharges white water vapor due to moisture entering after the engine stops. This is a normal phenomenon. However, if white smoke is still emitted after the engine is warmed up, it is a malfunction.

4. The reason and elimination method of the blue smoke from the exhaust pipe of the loader forklift?

The blue smoke from the exhaust pipe is a characteristic of burning engine oil. The main reasons and troubleshooting methods are as follows:

⑴ Engine oil level is too high.

The engine oil level should be checked, and the engine oil should be filled according to regulations.

⑵ The gap between the piston ring and the cylinder liner is too large or the piston ring is aligned.

The cylinder pressure should be checked. If the cylinder pressure is too low, the piston ring should be dismantled and inspected. If necessary, reassemble the four sets or replace the piston rings.

(3) The gap between the valve stem and the valve guide is too large or the valve oil seal is damaged.

The valve oil seal and valve fitting clearance should be checked, and the valve oil seal or valve guide should be replaced if necessary.

⑷The supercharger is damaged and leaks oil.

This kind of situation is mostly caused by the sudden blue smoke of the diesel engine, the supercharger should be repaired or the oil seal ring of the supercharger should be replaced.

5. What are the abnormal noises of the loader forklift diesel engine? What are the causes?

Diesel engines in good technical condition can hear a uniform and slight exhaust sound when idling; when running at high speed, it is a steady roar. If the noise increases, accompanied by power decline, fuel consumption increase, vibration intensification, etc., it can be judged as abnormal noise.

When the engine has abnormal sound, the sound can be judged according to the different technical conditions, different sounds, different working conditions and spatial positions of each matching pair, the location where the sound occurs and the characteristics of the sound, as well as the timing and changing rules of the sound, etc. types and possible causes.

Now the method of diagnosing abnormal noise mainly depends on human feeling and experience. Although some new diagnostic instruments have appeared, they have not been widely used.

Common abnormal noises and their diagnostic methods are as follows:

(1) valve knocking sound

There is a crisp metal knocking sound on the cylinder head cover, and the knocking sound is more obvious and crisp when the diesel engine is shifting at medium and low speeds. The regular "da, da" sound is mainly caused by excessive valve clearance. When the temperature of the diesel engine is raised or when the "cylinder broken" method is used for the test, the sound does not change. When the diesel engine is running at high speed, the knocking sound is not obvious because other mechanical noises are loud.

The main reasons for the excessive valve clearance are: the valve adjustment screw is loose, so that the screw is withdrawn or the moving parts of the valve mechanism (such as cams, tappets, rocker arms, etc.) are worn. When the valve clearance is too large, the diesel engine will be insufficiently inflated due to insufficient intake or exhaust, resulting in reduced power and increased fuel consumption. The valve clearance should be adjusted in time.

(ii) Piston pin ringing

The main reason for the ringing of the piston pin is that the piston pin, the connecting rod bushing or the piston pin seat hole are worn, resulting in an excessive fit clearance, and the piston pin impacts during motion and makes a noise.

The characteristics of piston pin noise are: when turning from idle speed to medium speed operation, the sound is more obvious; the period (frequency) of the sound changes with the rise and fall of the engine speed.

change. When the fuel injection time is advanced, the sound is more obvious and clear. After the engine temperature rises, the sound generally does not weaken, and sometimes it is obviously strengthened. Use the ?° cylinder breaking method?± test, the sound is weakened or disappeared.

(iii) The piston knocks on the cylinder

The common and most important reason for the piston knocking on the cylinder is that the piston and the cylinder wall are worn, and the fit clearance exceeds a certain limit. The piston swings during the up and down movement, and knocks the cylinder wall to make a sound of ?°dang, when?± sound. Sometimes, although the fit clearance does not exceed the limit, if the connecting rod is bent and deformed, it will also make noise.

The sound of piston knocking on the cylinder is obvious when the temperature of the diesel engine is low, especially when the engine is idling. The sound decreases or disappears as the temperature rises. This is characteristic of the piston knocking on the cylinder.

Since the knocking sound of the cylinder is similar to the sound of the piston pin, it is easy to distinguish.

A small amount of engine oil can be injected into the top of the piston from the injector seat hole, and after turning the crankshaft several times, start the diesel engine again. If the sound disappears immediately after starting, it is the knocking sound. It should be noted that when the oil supply is advanced (within the specified range), it will also cause a slight knock on the cylinder, which is a normal phenomenon.

(iv) Connecting rod bearing ring

The main reason for the ringing of the connecting rod bearing is that the journal and the bearing are worn, the bearing alloy layer is burned out, falls off, the bearing cover (tile cover) is loose, the bearing rotates (the bearing bush goes to the outer circle), and the moment of doing work collides with each other and makes a sound.

The characteristics of the connecting rod bearing noise are: the sound is obvious at medium speed, but not obvious at high speed due to the increase of other mechanical noises, and the sound is weakened at idle speed. When the temperature of the diesel engine changes, the sound does not change. In the medium speed range, when accelerating and decelerating, the sound will become louder as the speed increases. ? ° broken cylinder? ± test, the sound becomes smaller or disappears.

(v) Crankshaft bearing noise

The reason for crankshaft bearing noise is the same as that of connecting rod bearing. When refueling suddenly or suddenly decelerating, the sound is clear; if the bearing alloy layer is burnt out or falls off, the diesel engine will vibrate. During heavy-duty operation, the sound is obvious and clear. The sound does not change when the engine temperature changes.

When bearing noise occurs, the sound will not change significantly in the single cylinder?°broken cylinder?± test; the sound will become smaller or disappear in the adjacent two cylinders?°broken cylinder?± test. In addition, it can also be judged by touching the bearings of the outer body of the diesel engine with a metal rod or a wooden handle screwdriver. Note: If the noise is caused by the excessive clearance between the bearing and the bearing journal, the oil pressure will drop obviously.

(vi) Camshaft bearing noise

The most common and main reason for camshaft bearing noise is that the camshaft and bearing (shaft sleeve) are worn, and the fit gap is too large; the bearing alloy layer is burnt out, falls off, or the outer diameter of the bearing and the seat hole bearing? Camshaft bearing noise is an intermittent and rhythmic blunt ?°click, click?± sound, the sound is obvious at medium speed, and can also be heard at idle speed. Engine temperature changes or? ° broken cylinder? ± test, the sound does not change.

It can be seen that the abnormal noise of the diesel engine is mostly related to improper adjustment of the fit clearance and poor lubrication. Therefore, it is necessary to regularly check the fit clearance and maintain good lubrication for the running machine. For diesel engines with abnormal noise, they should be eliminated in time before use to prevent mechanical accidents from aggravated wear and tear.

6. What are the reasons for the breakage of the diesel high-pressure oil pipe of the loader forklift? How to prevent it?

The fracture of diesel high-pressure oil pipe is mainly caused by the internal stress generated during assembly and the bending fatigue damage caused by high-frequency vibration. The main reasons are:

(1) Improper position or loosening of the high-pressure oil pipe clamp

During assembly, if the position of the pipe clamp is incorrect or the pipe clamp is loose or missing, the installation rigidity of the high-pressure oil pipe will be reduced, and the natural vibration frequency of the high-pressure oil pipe will be reduced. When the natural frequency of the vibration of the high-pressure oil pipe is the same as the vibration frequency of the diesel engine , it will cause the high-pressure oil pipe to resonate, and a large vibration will occur to cause fatigue fracture in the middle or both ends of the high-pressure oil pipe.

(2) During the repair and assembly process of the oil pipe, the oil pipe is forcibly bent, causing stress at the sharp bend of the high-pressure oil pipe, and fatigue fracture occurs due to periodic vibration during fuel injection; the oil pipe is externally worn or has internal cracks during manufacture. High (generally around 20Mpa), causing the tubing to break due to cracks.

7. What are the reasons for the high oil temperature of the loader forklift torque converter? How to eliminate it?

The normal oil temperature of the torque converter is 70°C to 0°C, and the maximum temperature cannot exceed 20°C. If the loader is not working under heavy load conditions for a long time, the temperature of the torque converter rises rapidly and exceeds 20°C, which is abnormal. Note that the reason is to eliminate the method as follows:

① If the gearbox oil level is too low or too high, check the oil level of the hydraulic transmission oil and adjust the oil level to the specified oil level. The inspection method is: the loader runs for about 5 minutes, and the oil can be released from the oil drain switch on the gearbox. If too much oil is released, the oil is filled too much, and the oil should be released; if no oil is released, the oil level is too low, and hydraulic transmission oil should be added.

②The transmission pump is damaged or the pressure of the transmission control valve is low, which causes the transmission clutch to slip and heats up the oil. If the variable speed pump is damaged, the variable speed pressure cannot be adjusted, accompanied by heat or abnormal noise of the pump body, the variable speed pump should be replaced; if the pressure of the variable speed control valve is low, check and adjust the pressure to the specified value.

③ The hydraulic transmission oil has deteriorated and should be replaced with new oil.

If the loader continues to work under heavy load for too long, observe the indication of the torque converter oil temperature gauge at any time. Once it exceeds 0°C, reduce the load or stop it for cooling.

8. The reasons and troubleshooting methods for the low oil pressure in all gears of the loader forklift loader gearbox?

The normal working pressure range of the gearbox is .08～.47Mpa, if the pressure is lower than .08Mpa, but higher than 0.9Mpa, the pressure is too low. The main reasons and troubleshooting methods for the low pressure of the gearbox are as follows:

(1) The oil volume of the gearbox oil pan is insufficient, and the hydraulic transmission oil should be filled to the specified oil level;

⑵ The transmission oil filter is clogged, the cause of the clogging should be checked, and the oil filter should be cleaned or replaced;

(3) The oil suction pipeline from the transmission oil pan to the variable speed pump is poorly sealed, and the pipeline should be repaired or replaced;

⑷ The variable speed pump is seriously worn, causing internal leakage, and the variable speed pump should be replaced;

⑸ The pressure regulating valve of the variable speed control valve is improperly adjusted or the pressure regulating spring is damaged. Check whether the pressure regulating spring is damaged and readjust to the specified value;

⑹ The pressure regulating valve stem of the variable speed control valve or the accumulator piston is stuck in the valve body. The pressure regulating valve and accumulator should be disassembled for cleaning.

It should be noted that the deterioration of the oil will also cause the phenomenon of low oil pressure. The quality of the oil should be checked and replaced in time; the pressure gauge is inaccurate or the sensor is damaged, which will also cause the illusion of low pressure, and it should be repaired and replaced in time.

9. The reason and troubleshooting method of low oil pressure in a certain gear of the loader forklift loader?

In this case, generally the variable speed pump and the variable speed control valve work normally, and the fault lies in a certain gear itself. There are several situations:

(1) The pressure of the first and second gears is normal, but the pressure of the reverse gear is low. The reason is that the piston oil seal (piston ring) of the reverse gear clutch is damaged or the casing is cracked. Check the reverse oil cylinder of the case for cracks, and then check the oil seal for damage. The reason for cracks in the reverse gear cylinder is generally that the system pressure is too high.

(2) The pressure of gear and reverse gear is normal, and the pressure of 2nd gear is low. The main reason is that the rotary oil seal at the joint between the shaft end of the 2nd gear assembly and the gearbox end cover is damaged, or the oil seal at the joint surface of the end cover and the box is damaged; the piston seal in the 2nd gear clutch is damaged. The second gear should be disassembled, the rotary oil seal and related seals should be overhauled, and replaced if necessary.

(3) The pressure of reverse gear and 2nd gear is normal, and the gear pressure is low. This is because the sealing ring at the junction of the gear clutch assembly and the gearbox body is damaged or the piston sealing ring (piston ring) in the gearbox gear clutch is damaged. You should check whether the oil seal at the junction of the gear clutch and the box is damaged and disassemble it. Gear clutch oil cylinder, if necessary, replace the sealing ring.

20. There is a lot of foam in the hydraulic transmission oil of the forklift gearbox of the loader, and the reason why the loader is unable to walk?

There are a lot of air bubbles in the hydraulic transmission oil in the gearbox, because the oil suction hose joint between the transmission oil pan and the variable speed pump is not tightened or the hose is damaged.

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