I have a PC400 im working on and im having hyd problems I cant find. Everything works good but when you lift the bucket with a load in it, it gets real slow and you have to bump up the rpm, all other functions seem to be ok. I thought it might be a compensator but then that would effect everything. all the port reliefs look good I have good pressure. Im not familar with Komatsu, and hoping someone might be able to help!
Could you provide a Dash series and a serial number?
Its a -6 series. serial A80309. appreciate any info can give!
I'm thinking that should be early Dash 6 which I think used a Dash 5 hydraulic system with the Dash 6 electronics. At any rate have you checked for fault codes? Going back to the basics, I always started by checking all the things that affect engine horsepower first and then work my way through the electronics and finally go to the hydraulic system. I'll drain the junk off the bottom of the fuel tank to start with and then work my way up the line to the water separator if it has one and then the stainer in the banjo bolt. I would think your machine might have the Cummins engine so you won't have the strainer but might have the in line unit that looks like a gas filter for a car. Those have a brass strainer inside and can be blown out with air pressure. Make sure you blow it from the output side to the input side. I usually check the fuel filters by just poring them out across my hand. Any water will show up as bubbles that don't float. If I see any water at all I change them. Air filters need to be checked. Many times you can have a speed sensor on the bell housing burn out and it won't throw a code. Check them with an ohm meter. It seems to me they should be somewhere between 3 and 10 ohms of resistance. I never remembered figure because they fail to no resistance and full resistance. Speed sensor burn out because the bell housing get full of oil from a leaking rear main seal or input seal on the hydraulic pump. The level plug is underneath the pump. If it is full drain it down, put in a new speed sensor and monitor the level for a few weeks. If it doesn't climb you are OK. If it does you can decide when you want to repair it. To check machine performance on the quick I liked to do a cycle time test on the boom raise function. Stretch the stick all the way out, open the bucket all the way and set it all on the ground. Put the machine in the highest mode and time how quickly the boom goes from the ground to topping out. Generally it should be around 4 seconds. Anything over 5 seconds is usually too slow and the operators will gripe about it. Hopefully that will give enough to chew on for an hour or two. Let us know what you find. Good Luck!
How long the machine works? is it possible that the hydraulic oil mix with dust or something......
John C. -I have no codes and have tried everything you said. the only function is when you boom up with a load in the bucket. it gets slow as it warms up. am I missing relif valve or maybe a pump issue? i think these Komatsu's have a two pump flow . Vivian- I dont have any contamintion in the system. I have looked in filters and fluid as well.
gets slow as it warms up? i am not sure whether it is because of the high temperature that lead to the pressure relief. Try to down the flow, see what happen. if it is ok, maybe the pump got to fix. Hope it can be helpful.
I haven't worked on 400-6 machines so I'm limited in what I can tell you. If you can post a photo of the machine and the pumps I can probably tell which type of hydraulic system you have and possibly direct you on some troubleshooting. Just ignore the Chinese poster. The tag shows a photo of a woman but I believe it may be a kid or some bozo acting like they know something.
Even though you have a pre minor cHAnge unit with the cummins motor in it. You should still have the variable displacemnt pump system. So when you say you bump up the rpm's and the machine seems ok....you should be running at full throttle anyway.....it sounds like it is a simple issue. What work modes are working? Please advise.
John I think that this PC400-6 has the TVC-LS valve on the same valve located on the side of the front and the rear pumps. About the problem of the boom It is better to work on the boom circuit alone because the rest of the work equipment are good, so testing pressure compensationand safety suction is a good idea to start with.