Expert Tips for Buying a Used Excavator: Testing the Hydraulic System

When it comes to buying a used excavator, one of the most important things to check is the condition of the hydraulic system. Here are some tips for testing the hydraulic system to ensure that you get a good machine:

Test the operation

Start by testing each action separately. Begin at the bottom with the bucket and check whether it can be raised and lowered smoothly without hitting any structure or stopping short of the end. Then try pushing the bucket downwards to see if it can lift the entire machine. If it can, leave it in that position for a few minutes to see if it automatically descends. If it does, there may be a leak in the cylinder or valve core. Next, test the machine's movement by moving forward and backward simultaneously for about 10 meters. Check if there is any significant deviation from a straight path. If there is, it means that the oil circuit is not uniform and needs to be repaired. Then, try moving the machine unilaterally, both forward and backward, which should be possible in medium-speed mode. (It is common for machines to be unable to move unilaterally at idle speed, which is generally not considered a fault.) Finally, test the machine's turning function. There should be two types of movements: fast and slow. Check if the machine turns too slowly or too quickly in slow motion. If it moves too slowly, it means that the operation is inefficient, while if it moves too quickly, it may damage the machine. Also, test the turning brake performance. After the handle is stopped, the machine should turn a certain angle before stopping. If it turns 180 degrees or more, it is a problem that needs to be addressed. Generally, a range of less than 45 degrees is considered acceptable.

Test the sealing performance

For all bucket movements, sealing performance can be tested, but for machine movement, it can only be tested on a slope. Park the machine on a slope of about 20-30 degrees and leave it for half an hour. If there is any internal leakage in the walking motor, it will automatically slide down the slope. Test the turning function's stopping angle, and test the sealing performance of other working devices as follows: Turn the working device to the other side of the bucket, lift one end of the bucket and the other end of the working device. Ensure that each cylinder is under load, then lift it to a certain height. If the machine has no bucket, fill the bucket with soil (or something of similar weight), retract the bucket, and extend the boom to the highest point (or slightly lower). Leave the machine in this state for half an hour, then check which cylinder has the greatest change in stroke. Generally, for excavators that have worked for several thousand hours, a change of less than 10 cm is normal. Any change greater than that may indicate severe internal leakage, which will affect the machine's value.

Measure the pressure

This is a critical step but also a challenging one for non-professional assessors who may not have a pressure gauge or measuring connector with them. They can only rely on the method mentioned above to estimate whether the hydraulic system has enough force. Professional excavator assessors, on the other hand, will check the pump pressure, pilot pressure, and other pressure points in each movement to ensure that the pressure is sufficient.

Testing the hydraulic system is crucial when purchasing a second-hand excavator. By following these expert tips, you can ensure that the machine is in good condition and avoid potential problems in the future.

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