Air in Backhoe Hydraulics

[Unk]

Good Eve from Vermont, I have a 2004 Woods BH9000 W/PTO Pump (light to moderate use & low total hours)with air in the hydro system.The valves (all) make quite a squeling sound and "bubbling" hydro fluid is pushed up the fill tube and about a gallon overflows. I called Woods Equip. Co. (good tech help) and they advised me to look at all aspects of the suction line. I changed hose, replaced o rings, re-teflon taped, & retightened. But, the problem remains. Also, this winter the unit was frozen-up (-5 F)and would not react after I put the pump on and nothing worked.... I then drug it into a warm shop and changed the fluid 3 times, filter twice and double cheched that there was no water afterwards. Should I pressure and/or flow test at this point and could I have done any significant damage running the pump whith huydro fluid frozen?
Thanks,
Dave
Aka: Unk

 

[MrJimi]

WoW ! I want to welcome a first time post with a 2004 join date, Thats impressive.
I am no hydraulic expert but when I had air in my lines, the Case service told me to make all cylinders go all the way out and in and it would self bleed and it worked, it should work on yours and it's worth a try, get your machine warmed up and go for it
Jim

 

[Unk]

Thanks Mr.J-
Were your valves loud? did you have bubbles in your hydro fluid? I did try running the cylinders all of the way out and also ran the thing for some time. I'm getting a massive amount of very small bubbles evenly mixed in the fluid being pushed out of the fill tube when the resevour is topped off. The pume is quiet but the hoe is slightly slugish in reaction time and seems to have about 90+% of full power. Also, there are no hydro leaks. I'm wondering if I can do any potential damage to the pump by running it with this much air in the system.....
I have bought and sold on this site but, you are right it is my first in the discussion area...thank you for the southern hospitality!

 

[MrJimi]

Thanks Mr.J-
Were your valves loud? did you have bubbles in your hydro fluid? I did try running the cylinders all of the way out and also ran the thing for some time. I'm getting a massive amount of very small bubbles evenly mixed in the fluid being pushed out of the fill tube when the resevour is topped off. The pume is quiet but the hoe is slightly slugish in reaction time and seems to have about 90+% of full power. Also, there are no hydro leaks. I'm wondering if I can do any potential damage to the pump by running it with this much air in the system.....
I have bought and sold on this site but, you are right it is my first in the discussion area...thank you for the southern hospitality!

I'm not sure what I would call loud, it moaned and groaned a little and after a few full cycles in and out it was fine. I think the bubbles are OK, kinda like a hose in a bucket, it means it's flowing. And my fluid level is determined by a sight class about 3 inches tall and 1/2 inch in diameter and is shows level of fluid in reservoir but it is not even with the top, it's about halfway down. I'm reading this and it don't look as it's making any sense. My reservoir is never full and not supposed to be. Do you have a service manual for your unit or a good dealer nearby and I think any equipment dealer should be able to help you.
And the southern hospitality comes from being born and raised in Maine for 33 years and living here for another 33
I hope I have been some help to you and there are some great hydraulic experts here that will chime in
Jim

 

[JerryG]

If you run it for an extended amount of time with the bubbles going through the system, it will cause erosion to the pump.
If you have refitted all of the hoses, the air leak has to be in the valve body. I would say that an o-ring between the blocks in the spool valve is leaking. It can take on air and still not be leaking fluid to the outside.

 

[Unk]

Thanks Jerry,
Do you think I should take the Valve body apart at this point or do any additional testing like Flow or pressure on the pressure side of the pump or possibly at one of the cylinders.
Is it possinle the pressure releif valve is bad or the pump causing some type of cavitation?
Do you think the pump could have an issue from me running it while (for aprox 3 minutes) while there was water in the system and frozen (-5 F) ? Also,he pump does not get hot.
I just need to dig about 5 small septic holes Monday and then I can bring it to the barn and get it a closer look. I want to have some direction at that time.
Also, the reservoir is toped off to the full mark on the dipper....then when you start the PTO pump I loose about a gallon of fluid out the fill tube (a massive amount of very small bubbles mixed in).
Thanks,
dave

 

[JerryG]

Since it froze it is going to be hard to say where to start. Normally I would have said that it shouldn't be the pump or the valve body, but since it was frozen, there is a chance that the pump or the valve body has a crack. One thing for sure is that there is an air leak since there are bubbles in the system. I think that I would double check to see that none of the hoses or lines are leaking air. If they check out good again, then take the pump to a machine shop and have them either [SIZE=-1]use dye penetrant or [/SIZE]magnaflux to check it for a hairline cracks. Then the last thing I would check is the valve body.

 

[Unk]

Thanks Jerry,
I've double checked hoses and I will look at the pump closer.

Also, I wonder, even if there were no cracks in the pump (or valve body) if the freezing could do other damage...like to seals, etc. that could cause some kind of cavation.

How about the pressure relief valve?

Has any one heard of an obstruction causing cavation and the massive amount of bubbles that I'm getting?

I'm also considering putting a pressure and flow guages on it but I'm not sure if that would tell me where the problem is unless I start just after the pump...I guess...
Thanks all,
dave

 

[JerryG]

I don't think that the seals will cause a problem like that. If it was mine, I would now take the pump and have one of the test run for cracks. They don't charge very much to do that.

 

[john_bud]

Unk,

I think you killed the pump. Naturally, it's very hard to diagnose from this distance!

It depends on what and where the ice was. If the ice was on the suction side, the pump would have run dry, but 3 min shouldn't be a big deal. If the ice was on the pressure side BEFORE the relief valve, then the pump would have been dead headed. The pump casing can balloon, crack or have other "bad expensive" things happen and happen fast.

If possible, can you run an external clear line from the sump to the pump inlet and a clear line from the pump output to the res tank? That way you can see if the pump ONLY is the problem. Hopefully, it is ok.

If it isn't the pump, you still have a loose line on the suction side. Maybe a cracked fitting, clogged strainer screen, cracked filter housing, etc. Could even be ruptured line from water expansion. Look close with good light. These types of failures (suction) often don't drip much if any. 10-20 psi air pressure on the tank may help...




A secondary question is why you had so much water. Please find a water absorbing hydraulic filter (Donaldson makes them, but so do others) they are only about $1 more than a standard filter. Change them annually - before it gets to freezing.

 

[Unk]

Jerry,
You right, for the time and little money I'd have in it, I'll get it to a hydraulic shop and eliminate that as a problem...

BUT....

First, on John's recomendation I think I will do an extensive look see on the suction side...

John, are you also suggesting a restriction on the suction side (I.e.pluged strainer) with out pulling in air specifically....could possibly cause the cavatation/massive bubbling? This shows you how little I know about hydraulics.

If I have to replace the pump can any one recomend a source, quality brand at a reasonable or great price....other than starting cold with an internet search I wouldn't have a clue.

John, I'm not sure about the where and where the water came from; I bought thr rig used last year from a neighbor in summer and it sat till I picked it up in Janurary. But, Thanks for the tip on the water absorbing filter and changing before winter.
Thanks Again All,
Unk

 

[638]

You will NOT suck air on the pressure side of the system. That being said, if the suction screen is plugged, you could be pulling in air around the pump shaft seal or at any slightly loose fitting on the suction line.

ron

 

[Unk]

Ron,
Any possibility the relief valve on the valve body would cause something like this I.e. obstruction, malfunction, way out of adjustment?
The pressure side to pull air without leaking at 2500psi didn't make sense to me either...
I'm going to focus on the suction side and have the pump checked out but, I just can't help but wonder.
Ya' gotta have respect for anyone who does hydraulic work...
Thanks All,
Unk

 

[john_bud]

Ron,
Any possibility the relief valve on the valve body would cause something like this I.e. obstruction, malfunction, way out of adjustment?
The pressure side to pull air without leaking at 2500psi didn't make sense to me either...
I'm going to focus on the suction side and have the pump checked out but, I just can't help but wonder.
Ya' gotta have respect for anyone who does hydraulic work...
Thanks All,
Unk

NO possibility of bubbles from the pressure side. As 638 said, if the strainer or filter is clogged the pump can generate a lot of vacuum and cause air intrusion from places like pump seals etc. Get some spray oil (WD40 if it's all you have, but a thicker oil will be better) and spray it around the pump shaft, housing, hoses etc. Make a note if the sounds change.


Surplus center has hyd pumps.

Surplus Center - Hydraulic Equipment Electric Motors

 

[mikeykubota]

Sorry to post on another person question. But i am not sure on how to post a question I have a cub cadet 407 backhole attachment on my kubota tractor. and it has always work great But the other day I blew a cylinder on my backhoe. I change the cylinder and everything work great again. The next day went to use it and the all of the cylinders on the backhole was real slow. Talk to a lot of people about bleeding the air out everbody said it should come out by it self. Today i went out to see if i could get it to work and none of the cylindes was working except for the outriggers would go down real slow but they wont come back up, the front end loader on the tractor works great anybody have any idea what the problem could be

 

[J_J]

Those post are from 2007

You could start a new thread if you want to.

Post in this section. Cub Cadet Yanmar & CUTs on the forums page.

However,

Re-check the QD for the BH.

If you have a hyd gage, you will know if the QD's are not connected correctly by the back pressure reflected on the gage. With all valves in neutral, should be no or very little pressure on the gage.

In most cases, if air is in a cyl, it will eventually work itself out by you cycling the cyl .

If the cyls keep getting air, then you probably have a suction leak and you are aerating the hyd fluid . You need to find the leak. Try tightening all the clamps.

Look in the tank with a flash light and see if there are bubbles in there.

If the tractor has not been cranked up in a day or so, the air in the tank should have dissipated, so start the engine and look in the tank ans see if new air bubbles are being developed, and if so, then there is a suction leak.