As ground road construction equipment, bulldozers can save a lot of materials and manpower, speed up road construction, and reduce project progress. In daily work, bulldozers may experience some malfunctions due to improper maintenance or aging of the equipment. The following is a detailed analysis of the causes of these failures:
- Bulldozer won't start: After normal use, it won't start again and there is no smoke. The starter works normally, and it is initially judged that the oil circuit is faulty. When using a manual pump to pump oil, I found that the amount of oil pumped was sufficient, there was no air in the oil flow, and the manual pump could work quickly. This shows that the oil supply is normal, the oil line is not blocked, and there is no air leakage. If it is a newly purchased machine, the possibility of the fuel injection pump malfunctioning (the lead seal is not opened) is relatively small. Finally, when I observed the cut-off lever, I found that it was not in the normal position. After turning it by hand, it started normally. It was determined that the fault was in the solenoid valve. After replacing the solenoid valve, the engine worked normally and the fault was resolved.
- Difficulty starting the bulldozer: After normal use and shutdown, the bulldozer starts poorly and does not emit much smoke. When using a manual pump to pump oil, the amount of oil pumped is not large, but there is no air in the oil flow. When the manual pump works quickly, a large vacuum will be generated, and the oil pump piston will automatically suck back. It is judged that there is no air leakage in the oil line, but it is caused by impurities blocking the oil line. The reasons for oil line blockage are:
① The rubber inner wall of the oil pipe may separate or fall off, causing oil line blockage. Since the machine has not been used for a long time, the possibility of aging is small and can be ruled out temporarily.
② If the fuel tank is not cleaned for a long time or unclean diesel is used, impurities in it may be sucked into the oil line and accumulate in narrow places or filters, causing blockage of the oil line. After asking the operator, we learned that there was a shortage of diesel in the second half of the year, and non-standard diesel had been used for some time, and the diesel filter had never been cleaned. The fault is suspected to be in this area. Remove the filter. If the filter is dirty, replace the filter. At the same time, check whether the oil line is smooth. Even after these steps, the machine still doesn't boot properly, so that's ruled out as a possibility.
③The oil line is blocked by wax or water. Due to the cold weather in winter, it was initially determined that the cause of the failure was water blockage. It is understood that O# diesel was used and the oil-water separator never released water. Since no wax blockage in the oil line was found during previous inspections, it was ultimately determined that the fault was caused by water blockage. The drain plug is loose and the water flow is not smooth. After removing the oil-water separator, I found ice residue inside. After cleaning, the machine works normally and the fault is resolved.
- Bulldozer electrical failure: After night shift work, the machine cannot start and the starter motor cannot rotate.
① Battery failure. If the starter motor won't turn, the problem may be with the battery. If the battery terminal voltage is measured to be less than 20V (for a 24V battery), the battery is faulty. After sulfation treatment and charging, it returns to normal.
② The wiring is loose. After using it for a while, the problem still exists. After sending the battery for repair, it returned to normal. At this point I considered that the battery itself was new, so there was little chance of it being easily discharged. I started the engine and noticed the ammeter fluctuated. I checked the generator and found that it had no stable voltage output. There are two possibilities at this time: one is that the excitation circuit is faulty, and the other is that the generator itself cannot work normally. After checking the wiring, it was found that several connections were loose. After tightening them, the generator returned to normal.
③ Overload. After a period of use, the battery begins to discharge again. Since the same fault occurs multiple times, the reason is that construction machinery generally adopts a single-wire system (negative pole is grounded). The advantage is simple wiring and convenient maintenance, but the disadvantage is that it is easy to burn electrical equipment.
- The bulldozer's steering response is slow: the right side steering is not sensitive. Sometimes it can turn, sometimes it reacts slowly after operating the lever. The steering hydraulic system mainly consists of a coarse filter 1, a steering pump 2, a fine filter 3, a steering control valve 7, a brake booster 9, a safety valve, and an oil cooler 5. The hydraulic oil in the steering clutch housing is sucked into the steering clutch. The steering pump 2 passes through the magnetic rough filter 1, and then is sent to the fine filter 3, and then enters the steering control valve 4, brake booster and safety valve. The hydraulic oil released by the safety valve (adjusted pressure is 2MPa) flows into the oil cooler bypass valve. If the oil pressure of the oil cooler bypass valve exceeds the set pressure 1.2MPa due to blockage of the oil cooler 5 or the lubrication system, the hydraulic oil will be discharged into the steering clutch housing. When the steering lever is pulled halfway, the hydraulic oil flowing into the steering control valve 7 enters the steering clutch. When the steering lever is pulled to the bottom, the hydraulic oil continues to flow into the steering clutch, causing the steering clutch to disengage, and at the same time flows into the brake booster to act as a brake. After analysis, it is preliminarily inferred that the fault occurred:
① The steering clutch cannot be completely separated or slips;
② The steering brake does not work. 1. The reasons why the clutch is not completely separated or slipping are: external factors include insufficient oil pressure controlling the steering clutch. The pressure difference between ports B and C is not large. Since only the right steering is insensitive and the left steering is normal, it means that the oil pressure is sufficient, so the fault cannot be in this area. Internal factors include internal structural failure of the clutch. For internal factors, the machine needs to be disassembled and inspected, but this is more complicated and will not be inspected for the time being. 2. The reasons for the steering brake failure are: ① Insufficient brake oil pressure. The pressures at ports D and E are the same, ruling out this possibility. ②The friction plate slips. Since the machine has not been used for a long time, the possibility of friction plate wear is relatively small. ③The braking stroke is too large. Tighten with a torque of 90N·m, then turn it back 11/6 turns. After testing, the problem of unresponsive right steering has been resolved. At the same time, the possibility of internal structural failure of the clutch is also ruled out. The cause of the fault is that the braking stroke is too large.
Post time: Oct-17-2023