Is there another problem with the steering brake of the bulldozer? You'll know the reason after reading this!

1. Phenomenon

The so-called unresponsive steering refers to the situation where the driver loses the original steering speed when pulling the steering lever backward, that is, the mechanical steering response is sluggish. The poor steering of a bulldozer can be divided into poor steering on one side and poor steering on both sides. It feels difficult to move the steering lever when turning.

2. Cause analysis

① The viscosity of the working oil in the steering mechanism does not meet the requirements. When the pressure is too thick, it causes the oil flow rate in the hydraulic system to be slow, and the pressure increase rate of the oil acting on the piston is relatively slow. When the oil is too thin, it will cause excessive leakage in the system during operation, and also slow down the pressure growth rate acting on the piston, making the bulldozer unable to turn left and right smoothly.

② Insufficient hydraulic oil quantity causes the oil pressure in the hydraulic system to increase slowly, that is, the pressure acting on the piston increases slowly, resulting in slow disengagement of the steering clutch and causing the bulldozer to have poor steering.

③ Excessive impurities in the working oil cause oil blockage, making the steering on both sides of the bulldozer inflexible. If the oil passage of a control valve on one side is blocked, it will cause the blocked side to have difficulty turning.

④ Excessive wear of the gear pump has led to a decline in its conversion efficiency, insufficient working pressure, and failure to meet the steering requirements, resulting in the bulldozer's inflexible steering.

⑤ Improper adjustment of the steering clutch control mechanism, such as the free travel of the control lever being too small, causes the working travel of the steering clutch pressure plate to be too small when disengaging, resulting in incomplete disengagement of the steering clutch and poor steering performance.

When the adjustment clearance between the top rod and the push rod of the control mechanism is too large, the movement stroke of the spool valve of the control valve will be reduced, the cross-sectional area of the oil passage entering the inner cavity of the spool valve will be reduced, resulting in poor oil flow. This will cause the oil pressure acting on the piston to increase slowly, making the bulldozer unable to turn flexibly.

If the braking on one side of the steering clutch is poor or the steering clutch on the other side slips, it will also cause the bulldozer to have difficulty steering.

3. Diagnosis and Exclusion

The diagnostic steps for the malfunction of a crawler bulldozer not steering smoothly are as follows:

If the bulldozer fails to turn left or right smoothly, the fault is mostly within the hydraulic control system. It is necessary to check the oil storage volume, viscosity and contamination of the working oil in the system. If the oil storage is insufficient or the oil does not meet the requirements, it should be refilled or the oil changed.

If the working oil in the steering control system meets the requirements but the gear pump has been in use for too long, it may be that the gear pump is overused, and its oil pumping capacity has declined, which in turn affects the steering sensitivity of the bulldozer. The cause should be identified and repaired or replaced.

If a crawler bulldozer fails to steer smoothly on one side, it might be that the free travel of the control lever on that side is too large and should be adjusted.

Do not turn

1. Phenomenon

The so-called non-steering of crawler machinery means that the driver pulls the steering control lever backward and simultaneously steps on the brake pedal to keep the crawler bulldozer moving in a straight line.

2. Cause analysis

When a crawler bulldozer fails to turn, it must be that the steering clutch on the turning side has not disengaged, which prevents the power transmission from being cut off and keeps the running speeds of the tracks on both sides equal. The main reasons are roughly as follows:

① The free travel of the steering lever is too large. The space occupied by the swing of the steering lever in the cab of a crawler bulldozer is fixed. If the free travel of the steering lever is too large, its effective working travel will be too small. When it is insufficient to disengage the steering clutch, the crawler bulldozer cannot steer.

② When the transmission of the steering clutch control mechanism is interrupted, for instance, if the gap between the top rod of the steering control lever and the push rod of the power booster is too large, even if the control lever is pulled backward to the limit position, it is difficult to push the push rod to connect the oil circuit, resulting in transmission interruption during operation. The force required by the driver to pull the control lever cannot be transmitted to the steering clutch, that is, the steering clutch cannot disengage, and the crawler bulldozer cannot turn.

③ The steering clutch is rusted. When a crawler bulldozer is parked for too long in a damp environment, the steering clutch will rust. The rust products will fill between the driving and driven plates and expand, increasing the distance between the driving and driven plates and pressing the compression spring to the limit state. The rusted steering clutch will become an inseparable whole, preventing the crawler bulldozer from turning.

④ If there is no oil in the steering hydraulic system or the filter screen of the oil pump's suction pipe is severely clogged, there will be no transmission medium between the oil pump and the piston. As a result, the steering clutch cannot obtain the power required for disengagement and thus cannot disengage, and the crawler bulldozer cannot steer.

3. Diagnosis and Exclusion

If the crawler bulldozer was originally in good condition but does not turn when in use after being parked in a damp place for too long, it indicates that the steering clutch is rusted, causing the inability to turn. You can open the inspection hole to further investigate and remove the rust to eliminate the fault.

If a crawler bulldozer can only move in a straight line and cannot turn, it may be due to interrupted transmission of the steering control mechanism, no oil in the hydraulic system or severe blockage of the oil pipe, etc. The cause should be identified and eliminated.

If one side of the bulldozer cannot turn, it may be that the power transmission of the steering clutch control mechanism on that side has been interrupted. The cause should be identified and eliminated.

The brakes are not working or malfunctioning

1. Phenomenon

When the brake pedal is pressed for braking, the braking effect is not ideal, or there is no braking response.

2. Cause analysis

The main causes of brake failure or malfunction:

If the gap between the brake band and the driven drum of the clutch is adjusted too much, or if the gap between the two is too large due to the wear of the brake band after long-term use, when the driver presses the brake pedal with a constant force, the clamping force between the brake band and the clutch drum will decrease.

② Excessive free travel of the pedal reduces the effective braking travel.

③ Rust has formed at the connection points of each component of the braking system, causing excessive transmission resistance and reducing the force exerted by the braking band to grip the brake drum.

④ The friction coefficient of the brake band decreases, such as when the friction lining is oily, the friction plate hardens, the rivets are exposed, or they are too thin, etc.

⑤ The steering clutch is disengaged.

3. Diagnosis and Exclusion

Check the free travel of the pedal and press the brake pedal. If the free travel of the pedal is too large, it should be adjusted.

If it is very difficult to press the brake pedal and there is no sense of free travel, and the braking effect is also poor, it indicates that the transmission parts of the braking system are rusted and should be removed. The occurrence of this situation is mostly caused by parking for too long in harsh environments.

③ If the free travel of the pedal meets the requirements but the braking is poor, it indicates that the friction coefficient of the belt brake has decreased. Check whether there is oil on the friction plate, whether the oil on the rivets is exposed, and whether the friction plate is burned or broken, etc. Eliminate the problems based on the inspection results.

Braking drag

1. Phenomenon

When the brake is released, there is still friction between the brake band and the driven drum of the steering clutch. During the movement of the bulldozer, resistance is felt, and the brake band feels hot when touched by hand.

2. Cause analysis

The main causes of brake drag faults are:

The gap between the brake band and the driven drum of the steering clutch is too small.

② The return springs of the braking system lose their elasticity or break due to fatigue, resulting in the brake band being unable to return to its original position.

③ The brake belt and the driven drum of the steering clutch are rusted.

3. Faults and Diagnosis

Check the free travel of the pedal. If the free travel is too small and the surface of the brake band feels hot when touched by hand, it indicates that the braking clearance is too small and should be adjusted.

② After the brake pedal is released, if its free height is no longer at the highest position and it drops automatically when held to the highest position by hand and then released, it indicates that the spring force of the brake pedal return has decreased or broken, and it should be updated.

If the brake band and the steering clutch drum are rusted, they should be removed.