Common Maintenance Knowledge of Loaders
Sep 22 , 2023
1. What are the reasons why the articulated loader diesel engine "boils"? How to eliminate 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 causes and prevention and elimination methods of diesel engine "boiling" are:

(1) The inner wall of the radiator heat pipe (core) is scaled too thickly, which affects heat dissipation. Pay attention to adding clean cooling water during use;

And regularly remove scale in the water tank;

(ii) The radiator or cooling system is leaking, causing insufficient coolant. Check the cause of water leakage and add enough cooling water after troubleshooting;

(iii) The cylinder gasket or cylinder liner is damaged, and the high-pressure gas in the cylinder enters the water cooling system, causing the water tank to "bubble" and "boil" (in this case, it is often accompanied by diesel engine oil emulsification). The cylinder gasket or cylinder liner should be inspected for damage and replaced if necessary;

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

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

(VI) The thermostat is damaged, causing the large circulation to fail to open, causing the machine to overheat. The thermostat should be replaced.

It should be noted that loaders working in alpine areas will also experience boiling. The main reason is that the radiator freezes and the coolant cannot circulate widely. Therefore, when using a loader in alpine areas, attention should be paid to adding an insulation device to the front of the radiator.
2. What are the causes of black smoke from the diesel engine exhaust of loaders? How to rule it out?

When a diesel engine is working under load, the exhaust smoke color is generally light gray. It is normal for a diesel engine to emit black smoke from the exhaust when overloaded, suddenly accelerated, climbing or working under heavy load. However, it is abnormal to emit black smoke under no-load or low-load conditions or excessive black smoke under large-load conditions. The reasons and troubleshooting methods are as follows:

(1) The air filter is clogged, causing the cylinder to be underinflated. The air filter element should be cleaned or replaced;

(ii) The supercharger is faulty, causing insufficient air supply pressure and incomplete combustion of the diesel engine. The supercharger should be inspected;

(iii) If the fuel injector has poor atomization or oil dripping, the fuel injector should be inspected and inspected, and the fuel injection head (needle valve coupling) should be replaced if necessary;

(4) Improper adjustment of fuel supply time, there are two types:

a. Black smoke comes out of the exhaust pipe, and at the same time there is a crisp knocking sound in the cylinder, indicating rough work. This phenomenon is generally caused by premature oil supply. If the oil supply time is too early, it will usually cause starting difficulties.

b. Black smoke comes out of the exhaust pipe, and there is a flame in the muffler, making the sound dull. This phenomenon occurs because the oil supply time is too late. If the fuel supply time is too late, it often causes the diesel engine to overheat, increase the exhaust temperature, and may even burn out the parts.

In addition, if a diesel engine with an automatic fuel supply angle advancer emits black smoke at high speed, it may also be caused by damage to the automatic fuel supply angle advancer. The automatic fuel supply angle advancer should be disassembled and inspected. If the oil supply time is improper, it can be checked and adjusted according to the above method.
(5) Uneven oil supply to each cylinder

Black smoke is emitting from the exhaust pipe, the machine is vibrating seriously, and too much oil is supplied to individual cylinders. The "cylinder cutting method" can be used to check and eliminate;

(VI) Poor diesel quality

The quality of diesel is poor, resulting in poor atomization and incomplete combustion. The fuel tank should be cleaned and the diesel should be replaced.

3. What causes white smoke from the compact wheel loader exhaust pipe and how to eliminate it?

If there is water in the diesel or in the cylinder liner, the water will turn into steam and be discharged from the exhaust pipe, that is, white smoke will emit. The main causes and elimination methods of white smoke from diesel engines are:

(1) There is water mixed in the diesel oil. Check whether there is water mixed in the diesel oil;

(ii) 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, part of the fuel will be discharged with the exhaust gas before it can be burned, and the discharged oil mist will form white gas. When the thermal engine is under heavy load, the temperature of the combustion chamber and exhaust pipe rises, and the diesel fuel that cannot be completely burned 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 fuel injector

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

(iv) Water in the cylinder liner

The cylinder gasket is damaged, the connecting water channel or the cylinder liner is cracked, so that the cooling water continuously penetrates into the cylinder. During exhaust, the hot air flow is evaporated or dispersed, forming water mist or water vapor, and is discharged as white smoke. At this time, if you put white paper on the exhaust pipe

mouth, and fine water droplets will be sprayed on it. The cause of water leakage should be checked.

It should be noted that when the diesel engine is running cold, white smoke will continue to emit from the exhaust pipe. This phenomenon is more common when using diesel engines in cold winter. This is because the temperature inside the diesel engine cylinder is low, and the oil vapor on the cylinder wall evaporates and is discharged out of the exhaust pipe.

The exhaust pipe also discharges white water vapor due to moisture entering after the machine is shut down. This is a normal phenomenon. However, if the engine still emits white smoke after heating up, it is a malfunction.
4. What causes blue smoke from the loader exhaust pipe and how to eliminate it?

Blue smoke from the exhaust pipe is a sign of oil burning. The main reasons and troubleshooting methods are:

⑴The engine oil level is too high. The engine oil level should be checked and oil added according to regulations.

⑵ The gap between the piston ring and the cylinder liner is too large or the piston rings are aligned. The cylinder pressure should be checked. If the cylinder pressure is too low, the piston rings should be disassembled and inspected. If necessary, reassemble the four sets or replace the piston rings.

⑶The 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 situation is usually caused by the sudden emission of blue smoke from the diesel engine. The supercharger should be inspected or the supercharger oil seal ring should be replaced.
5. What are the abnormal noises of the loader diesel engine? What are the causes?

A diesel engine in good technical condition can hear a uniform and slight exhaust sound when idling; when running at high speed, it will roar smoothly. If the sound increases and is accompanied by reduced power, increased fuel consumption, increased vibration, etc., it can be judged as abnormal sound. When there is abnormal sound in the engine, it can be determined based on different technical conditions, different sounds, different working conditions and spatial positions of each matching pair, the location and sound characteristics of the sound, as well as the timing and changing rules of the sound.

Wait to determine the type and possible cause of the sound. The current method of diagnosing abnormal noise mainly relies on human feeling and experience. Although some new diagnostic instruments have appeared, they have not been widely used. Common abnormal noises and diagnostic methods are as follows:

(1) Valve knocking sound

There is a crisp metal knocking sound on the cylinder head cover. When the diesel engine is shifting at medium or low speeds, the knocking sound is more obvious and crisp. Regular "click, click" sounds are mainly caused by excessive valve clearance. The sound does not change when the temperature of the diesel engine rises or when the "cylinder cutoff" method is used for testing. When the diesel engine is running at high speed, the knocking sound is not obvious due to the loud noise of other machinery.

The main causes of excessive valve clearance are: the valve adjustment screws are loose, causing the screws to withdraw 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 under-inflated due to insufficient air intake or insufficient exhaust, resulting in reduced power, increased fuel consumption, etc. The valve clearance should be adjusted in time.

(ii) Piston pin noise

The main cause of piston pin noise is that the piston pin, connecting rod bushing or piston pin seat hole is worn, resulting in excessive fitting clearance, and the piston pin hits during movement and makes noise.

The characteristics of the piston pin sound 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. When the injection time is advanced, the sound will be more obvious and clear. After the engine temperature rises, the noise generally does not weaken, and sometimes becomes significantly stronger. Use the cylinder-breaking method to test and the sound will weaken or disappear.

(iii) The piston knocks on the cylinder

The common and most important reason for the piston to knock on the cylinder is that the piston and cylinder wall are worn and the matching gap exceeds a certain limit. The piston swings during its up and down movement and knocks on the cylinder wall to make a clicking sound. Sometimes, although the fitting clearance does not exceed the limit, the connecting rod will make noise if it is bent and deformed. The sound of piston knocking on the cylinder is obvious when the temperature of the diesel engine is low, especially when idling. As the temperature rises, the sound decreases or disappears. This is the characteristic of the piston knocking on the cylinder. Since the sound of cylinder knocking and piston pin sound are similar, in order to facilitate the distinction, you can inject a little oil into the top of the piston from the injector seat hole, turn the crankshaft a few times, and then start the diesel engine again. If the sound disappears immediately after starting, it is a knocking sound. It should be noted that when the oil supply is advanced (within the specified range), it will also cause a slight knocking sound, which is normal.

(IV) Connecting rod bearing noise

The main reason for the connecting rod bearing noise is that the journal and bearing are worn, the bearing alloy layer is burned out and falls off, the bearing cover (tile cover) is loose, the bearing rotates (the bearing pad goes on the outer circle), and the moment of doing work, they hit each other and make noise.

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

(5) Crankshaft bearing noise

The reason for the crankshaft bearing ringing is the same as that of the connecting rod bearing. Its characteristics are: the sound is duller than the ringing of the cylinder, piston pin and connecting rod bearing. When refueling or decelerating suddenly, the sound will be obvious and clear; if the bearing alloy layer is burned out or falls off, the diesel engine will still shake. During heavy-load operation, the sound is obvious and clear. The sound does not change when the engine temperature changes.

When bearing noise occurs, the noise will not change significantly in the single cylinder disconnection test; in the cylinder disconnection test of two adjacent cylinders, the noise will become smaller or disappear. In addition, you can also use a metal rod or wooden handle screwdriver to touch the bearings on the external body of the diesel engine to determine. Notice:

If the noise is caused by an excessive gap between the bearing and the bearing journal, the oil pressure will drop significantly.

(VI) Camshaft bearing noise

The most common and main reason for camshaft bearing noise is that the camshaft and bearing (sleeve) are worn and the fitting clearance is too large; the bearing alloy layer is burned out and falls off, or the outer diameter of the bearing and the seat hole of the bearing are out of circle. The camshaft bearing noise is an intermittent and rhythmic dull sound.

Heavy clicking and clicking sounds are obvious at medium speed and can also be heard at idle speed. The sound does not change when the engine temperature changes or the cylinder is cut off in the test.

It can be seen that abnormal noise in diesel engines is often related to improper adjustment of the fit clearance and poor lubrication. Therefore, running machines should regularly check the fitting clearance and maintain good lubrication. For diesel engines with abnormal noise, they should be eliminated in time before use to prevent increased wear and tear and cause mechanical accidents.
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