Our HST has some problems

[Qapla]

We have a NH TC40D with a FEL and BH.

Using it today I found a new problem ... I was trying to dig out a stump and when I positioned the tractor I discovered that the FEL will no longer lift the front off the ground. Even using the "tilt", it would not lift the front off the ground - it used to.

Also, when I had to drive out into the field quite a distance, I used Range II like I usually do. When I started, I was in "turtle", then I hit the button for "rabbit" and the machine bogged and almost died.

Later, we had a hose break and, when we brought the tractor over to take the hose off, we checked the hydro fluid dipstick. It did not show - the tractor was running.

Should we check the fluid with the tractor running or off? Also, would low fluid cause these other problems?

 

[texasjohn]

First, get the fluid level right. I. assume you lost fluid from broken hose. I check fluid with engine off.

Then repeat tests. Low hyd pressure could cause problems noted. Low fluid can result in low pressure if low enough.

 

[jinman]

Yes, low fluid could cause the problems. You just don't know how low it is if the dipstick is dry. You at least want some fluid showing on the dipstick. With the tractor running, it should read about the same level as long as the tractor is parked level.

You could also have an air leak around the main hydraulic filter or that rubber "T" that is bolted on the big hydraulic suction line coming from the filter. That "T" splits between the HST and the Main pump. If it is leaking both transmission and main hydraulics will have air and be weak. The "T" is right under the right-side operator platform in clear view and easy to get knocked around by brush and debris. Did you notice any bubbles in the fluid?

EDIT: If you find no leaks, the next thing is getting a pressure gage on the hydraulics to see what pressure you are running at about 2000 rpm. Full main system pressure on your tractor is 2500 psi.

 

[Qapla]

Update ...

We got the broken backhoe line fixed and made sure the hydro fluid was "correct" ... at least we think it is correct - it shows between the two marks on the dip stick.

The tractor ran fine in turtle and rabbit and the backhoe works fine and dug out a pine stump.

The front bucket was able to pick the stump up out of the whole and carry it to a burn pile. I was also able to dig dirt needed to complete the filling of the hole.

However, there still is no real down pressure on the front bucket. It acts as if it is in "float" mode. This causes it to not make a suitable grade as it will not level the dirt properly. It also will not lift the front off the ground to allow us to take the tires off.

Any ideas??

 

[JerryK]

Might just have air in the cyl's/lines... Run the FEL thru all its motions a few times.... That might help..

 

[jinman]

You could have a leak in a cylinder internal seal. Roll your bucket to dump position with the cutting edge down. Disconnect your dump/curl quick connects. Push down with the loader arms while backing up. Keep downpressure on the bucket cutting edge. If the bucket curls level, it is leaking internally. If it partially curls and then holds, then the seals are good. Internal leaks/bypassing can show up in strange ways, but when you disconnect your quick connects, it isolates your loader from the rest of the hydraulics.

Of course, you won't know for sure about your power until you check those pressures at the quick-connects with a pressure gage. Your tractor should have 2500 psi easily at around 2000 rpm engine speed.

 

[Qapla]

Update and additional info:

Used the tractor today and tried some of the things recommended. Still have problems.

A little extra info that I didn't think of before because it didn't seem to fit this problem ... but, one never knows.

Before the problems with the FEL we were using the tractor to dig up a stump. The tractor was lifted up on the stabilizers and the front bucket. I was digging when the tractor suddenly died. My BIL commented that I must have run out of diesel. I said I had not and was about to climb back on the tractor to see what was wrong. Suddenly, boom (well, kinda') and steam started billowing from the "passenger" side of the tractor. When the steam settled, we found that a "freeze plug" had blown in the side of the block. We later learned that it was not a freeze plug but the drain valve for the engine and that this is a problem with the NH. We took the tractor to the shop and they installed a new drain valve and also fixed a problem we were having with the glow plug timer and a broken pin on the BH bucket.

After we got it back from the shop is when we discovered that the FEL would no longer lift the front off the ground.

Today, I tried lifting the arms up and down to full limits to see if there was any air trapped. I also did the same with the curl. The bucket curls just fine.

However, I did determine that it is the lift arms that are not allowing the tractor to lift. With the bucket sitting on the ground, if I begin curling the bucket down, instead of lifting the tractor, the lift cylinders will begin to extend.

Now, when I lift the bucket all the way up it will do this just fine. When I lower it, it comes about 1/3 of the way down then there is a small snapping sound, like when a relief valve gives and a "bounce" in the FEL, then it comes the rest of the way down.

It does this every time I lift it all the way up.

I also noticed that some of the time it seems to be moving slower then it should when moving forward in turtle or rabbit, but seems to move fine in reverse. It does not always seem to do this. However, a couple times when I was going forward in high range and hit the rabbit button, it bogged down considerably before gaining speed.

We do not have a gauge to check the pressure.

Is this something that could be caused from the problem with the drain valve? Could the shop have left something "undone" that could be causing this? Is this something we should be able to fix or do we need to take it back to the shop ($$$$$$$) ?

 

[Leejohn]

Quote-----However, I did determine that it is the lift arms that are not allowing the tractor to lift. With the bucket sitting on the ground, if I begin curling the bucket down, instead of lifting the tractor, the lift cylinders will begin to extend.

Now, when I lift the bucket all the way up it will do this just fine. When I lower it, it comes about 1/3 of the way down then there is a small snapping sound, like when a relief valve gives and a "bounce" in the FEL, then it comes the rest of the way down.

That sounds like the piston is loose on one of the cyls.

 

[jinman]

With your bucket flat, put it all the way down as far as you can go with the lift arms. Disconnect the lift arm quick connects (both lines). Now, curl the bucket lip down to dump while watching the lift arms. If the lift cylinders extend as you curl toward full dump, then one or both lift cylinders is leaking internally.

By disconnecting the quick connects when the arms are down, you remove the joystick and all plumbing from the circuit except for the two lift cylinders and piping/hoses. If you quick connects hold as they should, the only way your lift arms can raise up is an internal bypass in one of the lift cylinders. If the lift arms move a bit and then hold firm, that's normal, but if the lift arms keep extending, then you have an internal leak. If the cylinders are the problem, I would just go ahead and rebuild both cylinders so they both match.

EDIT: Except for the main hydraulic filter and a short run of suction piping, your HST has nothing in common with the FEL hydraulics. I want to concentrate on the FEL problem rather than try to deal with two separate issues. Once the FEL problem is isolated, I'll try to address your HST issue.

One thing for sure, nothing you've indicated about the engine drain tap or the glow plugs could have any effect on the hydraulic system.

 

[Qapla]

jinman ... next time I am where the tractor is I will try that and see what happens ... could be a few days.