Hey Guys, I need some serious help with this one. This past weekend I changed the hydraulic suction and return filters on my 2000 Gradall 534D-6. Now the machine has a howling noise like the pump is cavitating and the machine does not want to move. I did not prefill the filters before reinstalling. The square cut o-rings in the filter housing were replaced as well. Prior to changing the filters I drove the machine a couple of miles to the shop. It ran about 15mph +-. Now, if I let the machine run and warm up for about 30 minutes it will begin to move but wot= 3-4mph. Pump pressure is 5600psi. I had a Caterpillar Tech come out to the job site yesterday and he spent about 4 hrs working and believed he fixed the problem. He said he tightened up the suction filter and everything began working just fine. I went out to the job site, started the machine and immediately heard the growling sound like a lack of fluid though it quieted down a little as the machine warmed up. Boom works just fine. So in the end, I replaced the filters with the exact same WIX filters that were on the machine and confirmed the cross-over filter numbers. Any suggestions or ideas would be followed by a world of appreciation. Thanks, Bob.
Those gradalls are very sensitive to air in the drive system. JLG calls for bleeding that system anytime you open it. Sounds like it's loosing prime almost like a fuel system. If the system is open anywhere all the oil will flow back to the tank and it will take a few minutes for the pump to have oil pressure everywhere it's supposed to be. I'm guessing the transmission is gonna need some internal parts. You CANNOT run that system out of oil.
First thing you need to do is figure out the vacuum draw on the inlet of the pump. You'll need a vacuum gauge and port adapters. Then you need to figure how aerated the oil is on the outlet. Youll need port adapters and a hose to run into a bucket. Don't run it for long. Compressed air on the outlet will destroy the pump
Wow. Any thoughts on the internal parts necessary?
I apologize for jumping straight to worst case scenario. The machine hydraulic pump is separate from the transmission. Being it is a hydrostatic system the they are much more sensitive to air in the system then a regular hyd system. If was ran any length of time with the pump howling the pump has internal damage. Maybe not enough to shut it down but it has a few less working hours on it then it did. If it's still howling you have a leak on the vacuum side. If the system is sealed air will work its way out. Just takes some time.
I am glad to report that my best friend and mechanic just finished up and the problem has been resolved. The brand new WIX filter on the suction side was the problem. Apparently they have some sort of bypass and if it fails, the fluid just sits and spins. The pump howled enough that most likely some life of the pump has diminished. Thank you all for your help and I hope that others read this post if they have problems. And we will see how CarQuest feels about replacing a pump and filter? Bob
Air in it is probably most of the problem.