The most complete collection of loader maintenance and repair methods in history (part 2)

27. The loader forklift boom lifts normally, but the bucket flips slowly and weakly?

The boom lifting is normal, indicating that the pressure of the working hydraulic system is normal, and the main reason is in the oil supply circuit of the bucket cylinder:

(1) If the pressure of the overload valve in the double-acting safety valve is improperly adjusted or stuck, the pressure should be checked to see if normal, and if necessary, the double-acting safety valve should be dismantled and inspected, and the pressure should be adjusted to the specified value.

It should be noted that the double-acting safety valve of some loaders is in the bucket cylinder, and if the bucket is weak, the bucket cylinder should be dismantled and inspected.

(2) The internal leakage of the bucket cylinder shall be checked according to the above method.

28. What are the reasons and elimination methods for the automatic fall of the loader forklift bucket (boom)?

(1) If the operating mechanism of the boom operating spool valve is improperly adjusted, so that the boom spool valve cannot be completely in the middle position, it should be checked whether the operating mechanism is adjusted in the center.

(2) If the piston seal ring of the boom cylinder is damaged or the cylinder barrel is damaged, resulting in serious leakage of the cylinder, the seal should be replaced or the boom cylinder should be replaced.

(3) If the stem of the spool valve of the boom valve is worn excessively and the seal is not tight, the distribution valve should be replaced.

(4) The safety valve on the distribution valve is damaged, causing internal leakage.

The method of judging whether the distribution valve or the oil cylinder causes the automatic lowering of the boom is: lift the boom to the highest position, put the boom valve stem in the middle position, listen to whether there is a sound at the boom cylinder, if there is a "bang, bang" sound, it is a fault for the distribution valve, if there is no sound, it may be a problem with the oil cylinder, and the cylinder should be dismantled and inspected.

29. When the loader forklift loader shovels and loads the loader, why does the bucket automatically turn up when it encounters a little resistance?

When the loader shovels the loader, the reason why the bucket encounters resistance and automatically turns up is that the pressure of the double-acting safety valve in the front cavity of the bucket cylinder is too low or the valve core is stuck in the open position, and the double-acting safety valve should be disassembled and inspected, and the pressure should be adjusted to the specified value.

30. When the loader forklift lifts the boom, the boom first instantaneously descends and then rises?

When the boom is lifted, there is a phenomenon of instantaneous descent and then rise, that is, the fault cause of the boom "nodding" is that the check valve in the boom reversing spool valve is worn and sealed poorly or stuck, and the distribution valve should be cleaned or replaced.

31. What is the reason for the noisy operation of the loader forklift working pump?

(1) If the suction pipe or oil filter is blocked, so that the oil inlet of the system is not smooth, the oil suction hose should be replaced or the filter should be cleaned or the filter element should be replaced.

(2) If the oil suction pipeline is not tightly sealed, the system will enter the air, and the oil suction pipeline should be overhauled.

(3) The working pump is swept and bored, and the side plate is worn out, and the working pump should be replaced.

(4) The viscosity of the hydraulic oil is too high, and the suitable brand of hydraulic oil should be replaced.

(5) If the pump shaft is not concentric with the drive shaft, check whether the drive shaft bearing is burned out and replace it if necessary.

32. Why is the working pump of the loader forklift easy to burst or the high-pressure hose of the working hydraulic system easy to burst?

The safety valve of the multi-way directional valve (distribution valve) in the working hydraulic system is improperly adjusted or the valve core is stuck, and the system oil pressure is too high, resulting in the explosion of the working pump casing or the bursting of the hose. Therefore, it should be noted that the pressure of the working hydraulic system cannot be adjusted at will.

In addition to the above reasons, the cause of a high-pressure hose burst can also be the aging of the high-pressure hose and should be replaced.

33. What is the reason why the hydraulic oil of the loader forklift is channeled into the oil pan of the gearbox?

The working hydraulics are not connected to the transmission hydraulics without any piping. Therefore, under normal circumstances, hydraulic fluid should not be channeled into the gearbox. The way for hydraulic oil to enter the gearbox is the joint surface of the working pump or steering pump and the gearbox (or torque converter).

The skeleton oil seal in the front end cover of the working pump or steering pump is damaged, resulting in the pressure oil leaking through the front pump cover and leaking into the gearbox along the pump shaft and the bearing seat hole or shaft hole of the gearbox housing.

In the case of an increase in the oil level of the gearbox, the front end cover of the working pump or steering pump should first be checked for oil leakage, and the skeleton oil seal should be replaced if necessary.

34. What is the reason why the handle of the reversing slide valve of the loader forklift distribution valve is too heavy?

There are two situations in which the reversing spool valve of the distribution valve is overmanipulated:

(1) The boom reversing spool valve and the bucket reversing spool valve are heavy, which is mostly caused by impurities in the hydraulic oil circuit or deterioration of the hydraulic oil. Hydraulic oil should be checked for replacement;

(2) The boom slide valve is working normally, and the rotary bucket slide valve is heavily operated. Since the bucket slide valve automatically returns by the return spring, if the return spring is not adjusted properly, it will cause heavy handling. The return spring of the spool valve should be checked and adjusted if necessary.

If the stem of a single spool valve is stuck, it will also cause the phenomenon that a spool valve is heavily operated, and the valve stem should be dismantled and inspected; Heavy handling of the new distribution valve may be caused by the tight fit between the stem and the valve body, and the mating clearance should be checked.

35. What is the reason for the fuel injection of the hydraulic oil tank of the loader forklift?

The main reason for the hydraulic tank to inject oil outward is that the oil contains a large number of air bubbles, which increases the compressibility of the oil.

Because when the oil flows back to the oil tank, it suddenly drops from high pressure to low pressure, and the air mixed into the oil expands sharply in the oil tank, and the pressure in the oil tank is higher than the atmospheric pressure, so that the oil is mixed with the air and discharged from the air vent of the fuel tank, forming a fuel injection phenomenon.

When there is oil injection, it is important to check the tightness of the oil tank to the working pump or steering pump line, as well as whether the oil pump itself is leaking.

It should be noted that in the oil return oil circuit, an oil filter is usually installed, and if the oil filter falls off, there may also be oil injection, and the oil sprayed out in this oil injection phenomenon does not foam much, which is the difference between the air mixed with the working hydraulic system.

36. What are the reasons for the heavy steering wheel when the hydraulic power steering system of the loader forklift is turning?

(1) The steering slide valve is stuck, and the steering valve should be disassembled and inspected;

(2) The fixing nut of the steering valve spool valve is over-tightened, the bottom cover is disassembled, and the nut is returned 1/4 turn, but it cannot be too loose, otherwise it will cause the loader to turn to the ± swing bucket.

37. Loader forklift hydraulic power steering system, the reason why the steering wheel is too empty and how to eliminate it?

(1) If the gap between the rack nut and the steering arm of the steering machine is too large, the gap should be adjusted;

(2) If the gap at the end of the follower rod assembly of the direction machine is too large, the reason for the excessive gap should be checked and adjusted.

38. In the hydraulic power steering system of loader forklift, the reason for the slow and weak steering and the elimination method?

(1) The steering pump is seriously worn and the steering hydraulic oil flow is insufficient, so the steering pump should be replaced;

(2) If the pressure of the constant flow valve is too low, adjust the pressure of the constant flow valve to the specified value (generally about 9.8Mpa);

(3) If the sealing ring of the steering cylinder is damaged or the cylinder barrel is worn, the sealing ring or the steering cylinder should be replaced;

(4) The steering valve has serious internal leakage, and the steering valve should be replaced.

When the steering is weak, it usually also manifests as both left and right steering is not in place. The pressure of the constant flow valve should be measured first, if the pressure is normal, it may be caused by the leakage of the steering valve or the damage of the steering cylinder, and the steering valve should be further dismantled.

39. In the hydraulic power steering system of loader forklift, the cause and elimination method of hydraulic oil overflow from the steering wheel?

The reason for the hydraulic oil spilling from the steering wheel is that the skeleton oil seal on the upper part of the steering valve body is damaged, and the oil seal should be replaced.

40. What are the reasons for the heavy steering of the full hydraulic steering system of the loader forklift and how to eliminate it?

(1) If the oil suction oil circuit is blocked or the viscosity of the hydraulic oil is too large, the oil filter should be disassembled, cleaned or the hydraulic oil should be replaced;

(2) The slow turn of the steering wheel is light, and the fast turn of the steering wheel is heavy. This phenomenon is mostly due to insufficient oil supply to the steering oil pump, and the reason for the insufficient oil supply should be checked, and the steering pump should be replaced if necessary.

(3) The fast-turning steering wheel and the slow-turning steering wheel are heavy, and the steering cylinder is weak. This phenomenon is mostly caused by the failure of the check valve (steel ball) in the steering valve, and the steel ball should be checked for missing installation (newly repaired steering gear) or stuck by stolen goods.

(4) The steering is light when there is no load, and the steering is heavy when the load is increased. This situation is mostly caused by low pressure of the safety valve of the steering valve block or jamming of the valve core. The valve block should be dismantled and replaced, if necessary.

(5) The steering is sinking, there is foam in the oil, there is an irregular sound when turning, the steering wheel rotates, and the oil cylinder does not move when it moves. If this phenomenon occurs, it means that there is air mixed in the steering system, and the cause should be investigated.

(6) For the flow amplification steering system, the blockage of the pilot oil circuit will also cause heavy steering, and the pilot oil circuit should be dismantled and inspected.

41. What are the causes and elimination methods of the full hydraulic steering failure of the loader forklift?

(1) The centering spring is broken, and the steering wheel cannot automatically return to the center, so the spring should be replaced.

(2) If the toggle pin is broken or the opening of the linkage shaft is deformed, in this case, the pressure oscillation increases significantly, or even cannot be rotated, and the damaged parts should be replaced or the steering gear should be replaced.

(3) The double-acting safety valve in the valve block is damaged, and the valve block should be replaced.

After dismantling, washing, and assembling the steering gear, there may also be steering failure and increased oscillation, which is generally due to the wrong position of the rotor and the linkage shaft, resulting in the confusion of the oil distribution relationship, and the steering wheel is autobiographical or swings left and right.

42. When the flow of the loader forklift is amplified and steered, the reasons and elimination methods for fast steering and slow steering while steering are fast?

This failure is mainly due to the wrong number of adjustment gaskets at both ends of the flow amplification valve stem, and the number of valve stem gaskets should be adjusted according to the regulations.

43. When the loader forklift is fully hydraulically steered, the reason for the autobiography of the steering wheel and the elimination method?

(1) The valve sleeve of the full hydraulic steering gear is stuck, and the steering gear should be dismantled or replaced;

(2) If the centering spring in the steering gear is broken, the centering spring should be replaced;

(3) For the flow amplification steering system, it may also be caused by the failure of the flow amplification valve, and the flow amplification valve should be overhauled.

44. What is the reason for the self-oscillation of the steering wheel in the full hydraulic steering gear of the loader forklift?

The full hydraulic steering gear is equipped with a cycloidal metering motor composed of a rotor and a stator, and the inner spline hole of the rotor and the external spline shaft of the linkage shaft have certain position requirements, if it is not installed properly, it will cause oil distribution errors and cause oscillation.

The correct assembly method is to align the notch of the linkage shaft with the downward concave direction of the rotor teeth.

45. What are the reasons for the slow rise of air pressure in the brake system of the loader forklift and how to eliminate it?

(1) The air compressor works abnormally and the air supply is insufficient. The air compressor should be checked for air leakage, abnormal noise, and overheating.

(2) If the air circuit is not well sealed and leaks, check whether the pipe joints and rubber pipes are leaking, and tighten the pipe joints or replace the rubber pipes if necessary.

(3) If the combination valve of the oil-water separator leaks or the exhaust valve is not closed tightly, the cause of damage should be checked, and the combination valve should be replaced if necessary.

(4) Air leakage from the gas storage tank. If the gas tank itself has sand holes, cracks and air leakage, or air leakage from the water release switch and safety valve installed on the gas tank, the cause should be found out and the damaged parts should be replaced.

(5) If the brake valve is damaged and the valve core is not tightly sealed, the brake valve should be replaced.

46. After the loader forklift diesel engine stops working, the reason for the rapid drop in air pressure of the braking system and the elimination method?

After the diesel engine stops running, the air pressure of the braking system drops rapidly, indicating that the air compressor is working normally, and the failure of the pressure drop occurs after the air compressor, and the possible reasons are:

(1) If the gas pipeline system is poorly sealed, check whether the gas joints are loose, whether the rubber pipes are aging and cracked, and tighten the pipe joints or replace the rubber pipes if necessary.

(2) The combination valve of the oil-water separator is damaged or leaks and should be replaced.

(3) If the brake valve is leaking, the brake valve should be overhauled or replaced.

(4) Air leakage in the gas storage tank or leakage of the water discharge switch and safety valve of the gas storage tank. Inspect, repair, or replace damaged parts.

47. What are the reasons for the high air pressure of the loader forklift braking system and how to eliminate it?

The main reason for the high air pressure of the braking system is that the combination valve of the oil-water separator is damaged, and it should be stopped for inspection in time. If necessary, replace the combination valve.

48. What is the reason why the loader cannot walk when the loader cannot be put into gear after the loader is moving?

After the Skid Steer loader is activated, it cannot be put into gear. At this time, observe that the gearbox pressure gauge has no pressure, and the loader cannot walk. The reason is that the shut-off valve of the variable speed control valve is stuck, and the variable speed control valve should be dismantled and cleaned to check the reason for the shut-off valve.

Sometimes, the piston of the brake valve is stuck, which can also cause the loader to not walk, and the transmission valve is not pressurized. At this time, the brake caliper does not return to position and is in a braking state. The brake valve should be dismantled and replaced if necessary.

Generally speaking, after braking, the reason why the loader cannot be put into gear is that the shut-off valve cannot be returned.

49. What are the reasons for the insufficient braking force of the loader forklift service braking system and how to eliminate it?

When the brake pedal is pressed, the loader cannot effectively slow down or stop, which is a lack of braking force. The main reasons for the lack of braking force are:

(1) The air pressure of the braking system is insufficient

If the braking force is insufficient, you should first check whether the brake pressure is lower than the specified value, if the brake pressure is low, you should check the cause according to the inspection method mentioned above, and eliminate the fault.

(2) Insufficient brake fluid

Check the liquid level of the brake fluid, if the liquid level is low, check whether there is leakage in the brake hydraulic system, and add the same brand of brake fluid as required if necessary. If the brand of brake fluid used is different from the new brand of brake fluid, the original brake hydraulic system should be cleaned before adding the new brand of brake fluid.

(3) The hydraulic pipeline of the braking system is mixed with air

If air is mixed in the braking hydraulic system, due to the compressibility of the air, it will cause braking sluggishness and insufficient braking force. The air in the system should be exhausted.

(4) The afterburner pump is damaged

The piston sealing ring in the afterburner cylinder of the afterburner pump is damaged or flanged, and the hydraulic piston leather bowl in the afterburner pump is worn, so that the oil pressure is insufficient. The seal or bowl should be replaced.

(5) Oil leakage from the caliper body or brake piston leakage

The cause of oil leakage in the brake caliper should be checked, the sealing ring should be replaced, or the brake caliper assembly should be replaced.

(6) The friction pads of the brake caliper are seriously worn, and the friction pads should be replaced.

50. What are the causes and elimination methods of excessive brake fluid consumption of loader forklifts?

To ensure that braking is effective, the brake fluid level should be checked frequently. If excessive brake fluid consumption is found during the inspection, the cause should be identified and the fault should be eliminated before adding brake fluid. The main causes of excessive brake fluid consumption are:

(1) If the leakage is caused by aging and wear of the high-pressure hose, loose tubing joints or damaged seals, the leakage part should be checked, the joints should be tightened or the rubber pipes and seals should be replaced.

(2) If the rectangular sealing ring of the piston of the brake caliper is worn and leaking, the cause of wear should be checked and the rectangular sealing ring and dust ring should be replaced.

(3) The sealing ring at the push rod of the afterburner pump is damaged, resulting in the leakage of the brake fluid into the air chamber. The seal should be replaced.

51. When the loader forklift brakes, the brake disc screams, and the brake is overheated, why is this?

The main reasons for this phenomenon are:

(1) The brake pads in the brake caliper are worn, which makes the metal lining brake disc rub against and scream, and produces overheating. Brake pads should be replaced in time.

(2) The fixing bolt of the brake caliper is loose, and the brake caliper is tilted and falls off and interferes with the brake disc. The fixing bolts should be tightened.

(3) There is a metal foreign object between the friction pad of the brake caliper and the brake disc. It should be cleaned up in a timely manner.

If there is a screaming sound when the loader is moving, it should be checked and dealt with in time to prevent serious wear of the brake disc

52. The loader forklift ammeter does not indicate the charging status, and the reasons and elimination methods for insufficient or non-charging of the electrical system?

The ammeter in the dashboard of the loader does not indicate or point to the negative pole (some are flashing for the charging indicator), indicating that the electrical system is not charging properly, and the main reasons for abnormal charging are:

(1) The charging line should be overhauled if the charging line is in poor contact, the fuse pipe (wire) is fused, and the charging line is burned (broken circuit or tie iron). The generator drive belt is too loose, and the belt is tightened according to the regulations, otherwise the generator bearing will be damaged;

(2) If the voltage regulator is damaged, the voltage regulator should be replaced;

(3) If there is a fault inside the silicon rectifier generator (mostly boring or rectifier diode burned out), the generator should be overhauled or replaced;

(4) If there is a wire or poor contact with the wire, the circuit should be overhauled.

53. What are the reasons for the excessive charging current of the loader forklift and how to eliminate it?

(1) If the magnetic field wiring is broken or the magnetic field coil is short-circuited between turns, the rotor should be overhauled or the generator assembly should be replaced.

(2) If the battery is damaged, check whether the battery has a serious power loss or short circuit between the plates, and replace the battery if necessary. If the charging current is too large due to battery damage, it may burn out the generator or charging line after long-term use, and it should be repaired in time.

54. What are the causes and elimination methods of overheating of loader forklift generators?

(1) If the generator drive belt is too tight, adjust the tension of the drive belt;

(2) Sweep and boring inside the generator, check the reason for the sweeping and boring, and replace the generator if necessary;

(3) If the bearings at both ends of the generator are poorly lubricated or damaged, grease should be added or the bearings should be replaced;

(4) If the magnetic field coil is short-circuited, the generator should be dismantled and inspected.

55. What is the reason for the abnormal noise of the loader forklift generator?

There are two reasons for abnormal noise in generators:

(1) During the operation of the generator, the rotor and the stator assembly collide, and friction occurs, resulting in abnormal noise. The cause of the collision should be checked in time and repaired. If the friction is severe, the generator should be replaced. When this kind of fault occurs, it will be accompanied by a serious swing of the ammeter, failure to charge, etc., and the generator will also generate heat.

(2) The bearings at both ends of the generator sound. Mainly because of the lack of oil in the bearings or damage to the bearings. Grease should be added or bearings replaced in a timely manner.

56. The reasons and elimination methods for the electrical system of the loader and forklift often burn the bulb?

The main reason why electric loaders often burn large and small bulbs is that the voltage regulator is damaged or the regulator contacts are ablated, causing the voltage regulation to lose control, the voltage rises too high, and the bulb is burned out.