Hi Guys I have a kubota kx161-2 excavator and have an intermittent problem that has been going on for years now. I’ve been using the machine a lot lately and it’s driving me crazy Three functions are intermittently weak. The dozer blade, Swivel or slew and the boom offset. These are controlled but a zexel gear pump mounted on the side of the engine. When it’s weak it’s around 500psi Lately when I start using the machine it’s weak and usually comes good after half an hour or so but sometimes it can be painfully slow for hours on end. Not sure if it’s my imagination but we are coming into winter and it’s a fair bit cooler and seems to be happening more. I have removed the Main Prv and disassembled cleaned and reassembled multiple times. I’ve swapped it with an identical one to no avail. All other Prv’s of the blade, slew, and boom offset have been removed and cleaned with no difference. The main KYB pump that has is for the rest of the functions has been completely rebuild 20hrs ago. All other functions work well. Any ideas would be greatly appreciated! Thanks Danny
Good day Danny Do you have a hydrulic schematic for your machine I only have the third series? Kind regards Uffex
Good day Weakness in hydraulics cause by pressure loss as you describe the issue as intermittent it is less likely to be a pump. As to the best of my information that is a fixed displacement gear pump, all three functions work from that same pump. The only possibility of pressure loss common to all three is that of the relief valve, some small damage easily missed. Kind regards Uffex
Thanks Uffex, I agree however not only have I disassembled the prv multiple times I have swapped one from a known working pump with no change in weakness. Thanks Danny
This is going to sound weird but it seems to be temperature related. In the mornings it is slow but as the day heats up it comes good until the afternoon and evening when it gets colder and even hours of operation won’t bring it back to life?!
Good day Danny Is there a possibility that an obstruction is in the fluid floating around, suggest a filter check to see what you have caught up in the filters. Is there any history to these three functions or the pump which serves the circuit. I believe you have a KYB MCV I will check the archives and see if I can come up with a possible solution. Kind regards Uffex
Thanks Uffex, fluid has been changed 3 times in the last 300-500hrs with all the work I have done over the last few years. Each time the gauze filter in tank is removed and cleaned. The buildup is always very minimal. Are there any other hydraulic filters you know of apart from the one in the tank? As far as the pump is concerned it’s a Zexel brand I have had it off the engine and disassembled/inspected it at one stage and found it all clean and no signs of obvious wear and damage. The 3 functions it controls have never had issues and have worked correctly when the pressure is correct. the rotary joint has also new seals replaced throughout. Today I used the machine for 6 hours and it was slow for an hour, came good for the rest of the day. Now it’s evening and it’s back to being slow Thanks Again
Good day Danny Please loosen the pump fastning bolts pull back the pump and inspect the drive shaft. Kind regards Uffeex
Good day Danny Searched for possible cause simplified the schematic see attched. Kind rgards Uffex
Thanks Uffex, I’ve popped the pump back and inspected the shaft and it looks ok. No obvious wear. The thing that I can’t understand as it is intermittent. Blocked filter makes seems plausible to be me or maybe a casting with a crack in it that expands and contracts? thanks for your help Uffex
The suction filter in tank
Good day Danny Illustrated is the 161-3 but there is not so much difference in the tank - filters should help to find those the suction screen from what I could see did not look so clean. I suggest checkout the return filters for evidence but as those small gearwheel pumps are not so expensive I would be inclined to go for a change. Maybe it been subject to over pressure at some stage and displaced the end plate seals. When changing a pump be sure to back of the relief valve - bleed the fluid through the body and run for twenty minutes at idle. This advice comes from a major hydraulics manufacture which extends the life of the pump and minimizes any ingress damage. Adjust relief valve to specifications with full engine speed after the formentioned precautions. Kind regards Uffex