The situation when on a tractor Minsk Attachments stop lifting and often catch the operator at the most inopportune moment. Hydraulic system is the circulatory system of any agricultural machine, ensuring the operation of plows, buckets and other units. If you notice that the control lever is idling, and the hitch lowers spontaneously or does not respond at all, you must immediately begin troubleshooting.
Ignoring the problem can lead to serious consequences, including failure of an expensive hydraulic pump or jamming of the piston group. In this article we will analyze in detail the main causes of breakdowns, diagnostic methods and repair methods that can be performed in the field or in the garage. Correct understanding of the processes occurring in hydraulic system, will save you time and money on service.
The first thing to do when a malfunction is detected is to conduct a visual inspection and initial diagnostics. Often the problem lies not in complex internal breakdowns, but in trivial things such as low fluid level or a clogged filter. System pressure - a key parameter on which the performance of the entire node depends.
Main causes of hydraulic failure
There are several fundamental reasons why MTZ hydraulics may stop functioning. Most often, the problem lies in a violation of the tightness of the system or wear of working elements. Air trapped in the system causes a characteristic noise and reduces operating efficiency, making lifting jerky or impossible.
The second common cause is wear and tear. gear pump NSh-32 or NSh-50. Over time, the gaps between the gears and the housing increase, which leads to a drop in performance. The pump simply cannot create the necessary pressure to move the oil to the distributor.
⚠️ Attention: Operating a tractor with signs of cavitation (wheezing sound of the pump) is prohibited, as this will quickly lead to the destruction of the working pair of gears.
It is also worth paying attention to the condition hydraulic oil. If the fluid turns black, has a burning smell, or contains metal shavings, it must be replaced immediately. Dirty oil clogs the channels and accelerates wear of all rubbing surfaces.
Diagnostics and testing of the hydraulic pump
The check should begin with hydraulic pump, since it is the source of energy for the entire system. MTZ tractors are most often equipped with NSh type gear pumps. For initial diagnostics, start the engine and warm up the hydraulic system to operating temperature by running the distributor idle.
Check the connection between the pump shaft and the drive. If the splines are licked or the coupling rotates, the pump will not physically pump oil, even if it is working properly. Visually inspect the housing for cracks and leaks, especially in the area of the shaft seals.
A more accurate check can be carried out by disconnecting the pressure line and starting the engine for a short time (literally for a couple of seconds). If the pump is working properly, it should emit a stream of oil under pressure. However, this method is crude and does not provide accurate performance data.
The most reliable way is to measure pressure using a pressure gauge. Connect the device to the break in the pressure line. For a working NSh-32A pump, the minimum pressure should be at least 7.5 MPa (75 kgf/cm²). If the readings are lower, repair or replacement of the pump section is required.
- 🔧 Check the tightness of the pump mounting bolts and the condition of the elastic drive coupling.
- 💧 Make sure that the suction pipe does not suck in air (check the clamps and hoses).
- ⚙️ Assess the condition of the gear teeth - they should not be chipped or worn out.
- 🌡️ Measure the temperature of the pump body after operation - strong heating indicates low efficiency.
If the pump does not create pressure even at idle, further diagnostics of the distributor does not make sense - you need to start with replacing or repairing the pump.
Checking and adjusting the distributor
Hydraulic distributor P80 or its modifications are the brains of the hydraulic system, directing fluid flows. If the pump is working properly, but the linkage is not working, the problem often lies in a sticking spool or leaking valves. The spool should move smoothly, without jamming.
A common cause of failure is a clogged bypass valve or foreign matter getting under the valve ball. This leads to the fact that the oil is simply dumped into drain line, bypassing the hydraulic cylinder. It is also worth checking the safety valve, which may not be adjusted correctly.
To check the distributor, it is necessary to measure the pressure in the pressure line with the spool in the raised position (focus on the end). The pressure must correspond to the settings of the safety valve (usually 13-14 MPa for MTZ-80/82). If the pressure is low, try gently tightening the adjusting screw.
The secret to valve adjustment
When tightening the pressure adjustment screw, be sure to record the pressure gauge readings. Do not turn the screw more than half a turn at a time to avoid stripping the threads and damaging the spring.
Please note the condition flow machine and throttle washers. If the system operates jerkily, the patency of the channels may be impaired or the sealing rings on the spool rods may be worn out. The tightness of the “drain” cavity is checked by the absence of leaks with the handle in the neutral position.
Malfunctions of hydraulic cylinders and linkage
If there is pressure in the system, the distributor switches, but the bucket or plow does not rise, the problem may be hydraulic cylinder. The main malfunction here is the breakthrough of oil through the piston cuffs from one cavity to another. In this case, the rod may move slowly or jerk.
Check the cylinder rods for scoring and corrosion. Damaged chrome rod will quickly destroy new cuffs. Also inspect the lugs and pins of the hitch - if the mechanism is jammed due to lack of lubrication or misalignment, the hydraulics will not be able to move it.
Spontaneous lowering of the hitch often indicates wear of the piston seals or loose valves in the distributor. For diagnostics, you can try raising the hitch and turning off the engine. If the descent occurs quickly, then there is an internal oil flow.
- 🔩 Inspect the fingers and bushings of the hinged mechanism for backlash.
- 💦 Check the external rod seals for oil leaks.
- 🚜 Make sure that the weight of the attachment matches the lifting capacity of the tractor.
⚠️ Attention: When replacing hydraulic cylinder cuffs, use only a lubricant compatible with hydraulic oil, and never use grease or lithol, as they can destroy the rubber seals.
Problems with hydraulic oil and filters
The quality of the working fluid directly affects the resource of the entire system. Using the wrong oil, such as motor oil instead hydraulic, or mixing different brands of oils can lead to foaming and loss of lubricating properties.
Be sure to check the condition hydraulic filter (if it is installed in your tractor model) and the oil intake screen in the tank. A clogged mesh creates a vacuum at the pump inlet, which causes cavitation and starvation of the system. The screen should be cleaned every time the oil is changed.
Foaming oil is a sure sign of air getting into the system or the presence of water. The foamed liquid is compressed, making the hydraulic cylinders sluggish and unstable. Let the system settle or replace the fluid completely if it has lost its properties.
Use MG-22-V or MG-30-V oil for all-season operation. In winter, special hydraulic fluids with a low pour point can be used.
The table below shows the main parameters of oils recommended for MTZ hydraulic systems:
| Oil brand | Viscosity (at 50°C) | Temperature range | Note |
|---|---|---|---|
| MG-22-V | 19-25 mm²/s | -10 to +70°C | Standard all season |
| MG-30-V | 27-33 mm²/s | From 0 to +80°C | For summer use |
| VMGZ | 10-14 mm²/s | -35 to +70°C | Arctic, low viscosity |
| MGE-46V | 41-50 mm²/s | From +10 to +80°C | For harsh conditions |
Elimination of system airing
Air in hydraulics is enemy number one. It is compressed, unlike a liquid, so the pump's energy is spent compressing the bubbles rather than lifting the load. Symptoms of airing include jerking of the rod, foam in the tank and the characteristic whine of the pump.
To remove air, it is necessary to raise and lower the hitch several times until it stops without load. If this does not help, check the suction line for leaks. Air is often sucked in through cracks in hoses or loose clamps that are not visible during visual inspection.
Sometimes forced bleeding of the system is required. To do this, loosen the screws securing the high-pressure pipelines (carefully, positioning the container) and allow the pump to expel the air lock. After this, the connections are tightened.
☑️ Checklist for pumping hydraulics
Frequently asked questions and answers (FAQ)
Why does the hydraulic cylinder lift the load only jerkily?
Jerking most often indicates the presence of air in the system or that a pair of gears in the pump have worn out and it cannot provide a uniform flow. The cause may also be air leakage through the pump rod seal.
What pressure should be in the MTZ-80 hydraulic system?
The nominal pressure in the pressure line when working with mounted implements is 13 MPa (130 kgf/cm²). The safety valve shut-off pressure is usually set to 14-14.5 MPa. To work with active trailers, a pressure of 19-20 MPa is required.
Is it possible to use gear oil in MTZ hydraulics?
The use of TAp-15V oil or analogues is allowed only in emergency cases and for a short period of time. It has a different viscosity and additive package, which can lead to accelerated wear of the pump and overheating of the system in the long term.
Why does the hitch lower itself under load?
Spontaneous lowering indicates a leak in the system. This could be wear on the hydraulic cylinder piston cuffs, a loose fit of the “no-flow” valve in the distributor, or wear on the plunger-bushing pair in the pump.