Update:Now the Gear Pump is replaced, (the good thing is that the formed owner took the cost) but the hydraulics are still slow and jumpy. I think it can be either a leak on the suction side or some "reduction valve". As skidsteer.ca says it can be a leak, right now most of the inside of the machine is full of oil, as that happend during the Gear Pump Replace so a leak is today hard to find. Note: I have still NOT replaced the hyd. oil filter. HELP!?
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There is usually a red push in plastic plug in the pump in a port right next to the input shaft that has to come out before you install the pump as once it is mounted you can't get to it , did you take that plug out ---------is your drive belt going to the pump tight and not slipping --------are you still foaming (bubbling ) up the oil ---------when ever you change a pump you should change the filter before you crank it up as trash may have been in the system and you may have trashed the new pump
Hi, as I was not the one that replaced the pump, (it was a mechanic hired by the former owner) I know nothing about the "red push plug" I hope the mechanics did otherwise they have to do the same work again. But as the machine have the same problem before/after the pump is replaced i guess the plug is not there. I think it cannot be the drive belt as it´s pretty tight. Yes I know about that I should have replaced the filter, but it looks new - even on the inside, and I think someone have tried to fix the problem earlier by replacing the filter. It lookes brand new. I really dont know about the foaming I havn't looked into the hyd tank yet, but when I looked on the oil on the oil slick it looked very good and not full of bubbles. When I tilt/lift the hydraulis it sort of groans, can this be the "relif valve" - or can if be a valve that does not closes/opens fully? I think the best for me is to take it to a Bobcat dealer for a flow meter test.
Groaning is usually air in the system. The system should self bleed with use but they way you have been talking the problem is still exactly the same no matter what. It really does sound like what happens when you have a blocked filter, it causes the oil to foam up. This usually only causes problems in the drive section and not the lift and tilt functions! I had this problem with an old 731 i had, the hydraulics were super tough but the drive was gutless, cleaned the filter and it was perfect. It was foaming the oil and you could hear it groaning and squeeling but ONLY while driving.
I would give your dealer a call and see what they have to say, their service depot is really helpful. They will take the time to think about the problem and look it up for you, they may have encountered this before or at least know where to start looking.
You have no leaks? all i can think of its drawing air in through a loose fitting but usually these will at least leak a little.
OldMachinist
Well-known member
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- May 24, 2006
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After having the system open to replace the pump there will be alot of air in there. How long did you run it to try and clear the air? Here's how I was told to purge the system.
Run throttle about half way slowly drive forward on a level suface and lift the bucket almost to the max. You don't want to max it out because then the relief valve will open. Tip the bucket slowly down and up while bringing the boom down. Again you don't want max it out in ether direction. Do this five or six times then let turn it off and let it sit for a couple of hours and try it again. If its better do the purging again until it runs like it should. The suction and system return line are connected together on this machine and any air that gets in is recycled thru the pump. If this doesn't clear the air from the system then air is still being sucked in or the anti-cavitation valve needs cleaned or replaced.
The anti-cav valve is on the front of the valve body. It is the large plug above the tilt spool. Take it out and clean it. You should replace the oring and backup washers too. It gets torqued to 35-40 ft lbs.
More than likely the suction/return hose is leaking. Like I said in my earlier post the suction hose is at the bottom of the hydraulic tank behind the battery. It is nearly impossible to do anything but check it for leaks with engine in the machine. You need to clean all the oil and gunk from around it and let it sit overnight to check for a leak. Even a very small leak on the suction side will allow a lot of air in to the system. When your in there cleaning around it try to see it will move any at all. If its loose its sucking air. You can try to tighten it but I found no way to do this with the engine in place.
Good Luck
Thanks all folks for your tips! Today I talked to the Bobcat shop, and they will take a look at it tomorrow, now it is also leaking oil, so I guess this leak is on the suction side, most likely the hose below/in front of the engine, that goes from the tank to the gear pump. I´ll report the result here.
I hope they sort it out for you quickly and cheaply! They work on these machines all the time so i'm sure they won't waste any time fixing the problem. I wish i knew all their tricks to fix things without spending most of the day getting to the broken part!
Solved this - as the seller now have replaced the machine - case closed! Thanks all folks for your help! I think the problem was a leak in the hose from the tank to the gear pump.
