Changed hydraulic fluid - now don't have any hydraulics...

[mahlers]

I'm sure this is an easy one, but I couldn't find anything in my owners manual that points me in the right direction - so obviously I come back to TBN.

I just changed out my hydraulic fluid and all the filters on my TN70S, and now I have no hydraulics. I drained fluid from all the places the manual told me (from the main resevoir, from under the 3-PH arms, and from the 4WD housing), and filled up the filter as much as I could before reinstalling it. I'm sure I need to bleed the system - is there a bleed screw someplace on the hydraulic pump? What's the proper procedure for bleeding the air out?

Thanks in advance for any help!

Martin

[gordon21]

Did you start the engine and cycle the FEL controls? If you have power steering, then turn the wheel lock to lock a couple times. Raise the 3PT hitch up and down a couple times. Then go check the fluid level again. Chances are you will be a quart or more low.

[mahlers]

Thanks very much for the quick reply! Yes, I did cycle the power steering to each side a couple of times. Unfortunately I can't cycle the 3PH because I have a backhoe installed and the arms are under the backhoe assembly.

[gordon21]

Even better you have the backhoe mounted. Cycle all the backhoe functions back and forth. You have a couple gallons of OLD fluid in the hoe that did not get changed. You now have probably 4-5 gallons of new fluid and 2 gallons of OLD fluid that will intermix once the system is bled. If you have a FEL, you also left a gallon or two of old fluid in those hoses and cylinders. There is no way short of dismantling all your hydraulics to change the oil completely.

Change what you can and move on. If the old oil bothers you, do another oil change and you will get rid of 80% of the old oil and 80% of the new oil and you will STILL have some of the original oil left in the system.

[mahlers]

I'm not too worried about the oil mixing - the oil was still pretty fresh, and the main sump holds over twelve gallons of oil that I drained out and replaced, so whatever's left in the implements is going to be outnumbered in a big way. Also, I went with Kubota Super UDT this time around to better handle water content in the oil - so overall I'm not worried about mixing a few gallons of old fluid in with the new.

Problem I'm having is that none of the hydraulic controls work at all, except for the power steering. So I'm assuming the main hydraulic implement pump is air bound and can't get a prime.

[dqdave1]

Is Kubota Super UDT approved oil for the unit? Or should I say; does it meet or exceed specs?

[mahlers]

Yes, Super UDT exceeds all the specs and from what I've read, it is the hot ticket for those of us that really work the heck out of our hydraulic systems. I don't have any first-hand experience yet -because the whole system is sitting idle while I try to figure out what's keeping my hydraulic system asleep.

[erosol]

Did you add new oil and start the engine, then check the oil level? Let the engine run for awhile and it will get the air out and should work. Or let it sit over night, then try it. I will come around and work soon, don't worry. Maybe it's just tired and wants a break from work.

[jinman]

Yes, Super UDT exceeds all the specs and from what I've read, it is the hot ticket for those of us that really work the heck out of our hydraulic systems. I don't have any first-hand experience yet -because the whole system is sitting idle while I try to figure out what's keeping my hydraulic system asleep.

You don't want to run that hydraulic pump for very long without fluid. It will self-destruct without fluid for internal lube and cooling. Letting the tractor set overnight and trying again is a good choice, but I think I'd check with my dealer's service manager to see if they have some tricks. It might be as simple as slightly pressurizing the reservoir, or opening a line somewhere to bleed out the air.

I'm sure you have a separate power steering pump and reservoir, so that will do you no good to cycle that.

[JC-jetro]

I'm sure this is an easy one, but I couldn't find anything in my owners manual that points me in the right direction - so obviously I come back to TBN.

I just changed out my hydraulic fluid and all the filters on my TN70S, and now I have no hydraulics. I drained fluid from all the places the manual told me (from the main resevoir, from under the 3-PH arms, and from the 4WD housing), and filled up the filter as much as I could before reinstalling it. I'm sure I need to bleed the system - is there a bleed screw someplace on the hydraulic pump? What's the proper procedure for bleeding the air out?

Thanks in advance for any help!

Martin

Martin,

I think your pump is cavitating. Gear type positive displacement pump are not designed to pump or compress air. You must get the air out of the system by bleeding it. The inlet pipe to the pump is almost always the larger diameter than the discharge. If you have a banjo pump connection on the inlet I loosen it up to see if I start seeing fluid. Obviously this will only work on siphon principal... the fluid height in the reservoir should be higher than the pump inlet to induce flow.You probably see combination of air and oil to come out of banjo fitting collect the oil in a clean container so you can return it to the reservoir. By doing so you are priming the pump. if the pump manages to get a slug of oil moved in the pipe ... then the vacuum action will suck the flow toward the pump inlet. Pump initially needs to be primed. Only diaphram or reciprocating pump with spring loaded intake and exhaust valve are able to self prime. As Jinman indicated refrain from running the pump dry. you will destroy the pump quickly without proper lubrication, oil film coefficient can only help damage for a short time.

JC,