Hello, I hope someone can help me. I have a 2003 Kobelco 80CS excavator. Hydraulic return and suction filters have been changed. In line pilot filter has been cleaned. Operating Symptoms
All functions work properly when working against gravity and when it is under loads. i.e. It has tremendous power to dig and load trucks.
Malfunctions are below: In summary, when an arm, bucket, boom, or swing pilot valve or combination of pilot valves are activated, the function(s) immediately responds if the function does not have “zero gravity”. It seems the first response is gravity, then to “zero gravity”, then slowly the function begins and finally kicks in as normal.
1. With boom up and arm extended, when the pilot valve for the arm only is activated either partially or fully for retraction, the arm seems to fall with gravity force (no initial push by arm cylinder). The arm falls to a hanging position (“zero gravity”), stops a few seconds, then slowly begins retraction and in another few seconds kicks into normal retraction speed until fully retracted. The same actions happen in reverse- i.e. when the arm is fully retracted and the pilot valve is activated to extend the arm, the arm falls to zero gravity, stops a few seconds, then slowly begins extension and in another few seconds kicks into normal extension speed until fully extended. If the boom pilot and arm pilot are activated at the same time, there is no change to the arm action either in retraction or extension.
2. With boom up and arm extended, the bucket performs just as in #1 above.
3. With the boom up, when the boom lowering pilot valve is actuated, the boom lowers – again with gravity. Once the bucket hits the ground, the boom stops, waits a second or two, then begins to lower and raise the machine as it should. If the bucket is sitting on the ground and the boom pilot is actuated to raise the boom, it hesitates a second or two, and then begins to raise as it should.
4. Swing: with the machine sitting level, swinging right and swinging left operate properly. When the machine is not level, and the swing pilot is actuated, the swing direction begins but then coasts when the gravity is pulling downhill; once the machine gets to “zero gravity” it either stops or hesitates, then begins to swing again as it should. (Operates the same in both directions)
5. Travel: When one or both travel pilots are actuated and the machine is going uphill – under load (either forward or reverse – but uphill) the machine operates properly. When going downhill and both travel pilots are actuated, the machine goes, stops, goes, stops in a very jerky motion. Sometimes if the machine is turned to engine idle and both pilots are activated while going downhill, the machine will not jerk--- but other times it does. If going downhill and one travel pilot is actuated further than the other, sometimes the jerking will stop – seems to depend on steepness of the hill.
All functions work properly when working against gravity and when it is under loads. i.e. It has tremendous power to dig and load trucks.
Malfunctions are below: In summary, when an arm, bucket, boom, or swing pilot valve or combination of pilot valves are activated, the function(s) immediately responds if the function does not have “zero gravity”. It seems the first response is gravity, then to “zero gravity”, then slowly the function begins and finally kicks in as normal.
1. With boom up and arm extended, when the pilot valve for the arm only is activated either partially or fully for retraction, the arm seems to fall with gravity force (no initial push by arm cylinder). The arm falls to a hanging position (“zero gravity”), stops a few seconds, then slowly begins retraction and in another few seconds kicks into normal retraction speed until fully retracted. The same actions happen in reverse- i.e. when the arm is fully retracted and the pilot valve is activated to extend the arm, the arm falls to zero gravity, stops a few seconds, then slowly begins extension and in another few seconds kicks into normal extension speed until fully extended. If the boom pilot and arm pilot are activated at the same time, there is no change to the arm action either in retraction or extension.
2. With boom up and arm extended, the bucket performs just as in #1 above.
3. With the boom up, when the boom lowering pilot valve is actuated, the boom lowers – again with gravity. Once the bucket hits the ground, the boom stops, waits a second or two, then begins to lower and raise the machine as it should. If the bucket is sitting on the ground and the boom pilot is actuated to raise the boom, it hesitates a second or two, and then begins to raise as it should.
4. Swing: with the machine sitting level, swinging right and swinging left operate properly. When the machine is not level, and the swing pilot is actuated, the swing direction begins but then coasts when the gravity is pulling downhill; once the machine gets to “zero gravity” it either stops or hesitates, then begins to swing again as it should. (Operates the same in both directions)
5. Travel: When one or both travel pilots are actuated and the machine is going uphill – under load (either forward or reverse – but uphill) the machine operates properly. When going downhill and both travel pilots are actuated, the machine goes, stops, goes, stops in a very jerky motion. Sometimes if the machine is turned to engine idle and both pilots are activated while going downhill, the machine will not jerk--- but other times it does. If going downhill and one travel pilot is actuated further than the other, sometimes the jerking will stop – seems to depend on steepness of the hill.
Kobelco 80CS Excavator
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