TC40DA hydraulics not working but hydrostat is

[gretchen8]

I can't get my picture to post. The part making noise is bolted on the side of the engine on the right side if your sitting on the tractor. It sounds as if it is cavatating and doesn't have fluid going thru the big 1" size pipe, BUT every now and then it will catch and it will change sounds and the hydraulics will work until it loses prime.....I'm guessing.

 

[J_J]

Remove the pump and check the shaft. Cavitation is not a good thing. If the pump is cavitating, it is having trouble getting fluid. Need to fix that ASAP.

 

[jinman]

Sorry I did not see this post until this morning, but there are two things you need to check, the seal where the big pipe connects to the pump (on top), and the rubber boot under the right side operator's platform.

I think your pump is cavitating because it is drawing air. I would spray or pour some oil around the inlet to the pump and observe if the cavitation stops or the oil is drawn into the fitting at the pump, indicating the o-ring seal is leaking. If this fitting and the bolts are tight, this is probably not the case.

Under the right side operator's platform, there is a big rubber "T" that is held in place with hose clamps. It's really easy to hit some brush and loosen this fitting or even punch a hole into it. If it is loose or damaged, your hydraulic pump is probably sucking air and cavitating. This "T" is where the oil comes out of the big filter and splits to go to the HST transmission and to the hydraulic pump. Both the HST and Main Pump draw fluid though the big filter between the right rear wheel and transmission case. The fluid then separates at the rubber "T" and goes to the HST and Main Pump. Your HST may be drawing some air too, but it has a charge pump that helps by doing most of the work of drawing fluid from the reservoir and supplying it to the main HST pump. Check the big rubber "T" and make sure the clamps are tight (snug). Don't overtighten the clamps. Like any hose clamp, they will fail if tightened too much.

You said the filter was 1/2 filled. This puzzles me.:confused3: How do you know that? Did you remove the main hydraulic filter? Is it possible that the filter is not seated properly and its gasket is leaking air into the system?

One last thing you should check is to pull the engine dipstick and check the oil level. If the oil level in the engine is way overfilled, there's a chance your main hydraulic pump has blown a seal. This happened to me earlier this year and it has happened to several others. If your engine oil is fine, don't worry about it. This is not your problem.

Please don't worry about disconnecting any quick connects or removing your loader if you need to do that. Your tractor is protected by a high pressure relief valve, but disconnecting the loader quick-connects won't cause any pressure to be felt at the main pump unless you operate the joystick while the loader QCs are disconnected. Even then, it's no big deal.

Please do not start taking apart your hydraulic pump. It is a pretty involved job to remove it and you want to make sure there is something wrong before ever doing that. (This is experience talking. . . )The main pump and the power steering pump use the same drive gear off the engine, so if something was wrong there, you'd not have any power steering and it would not partially work sometimes. I surely think that you have air leaking into the system somewhere.

I would caution you to not run the engine and main pump for long periods if it is not pumping some fluid. The hydraulic fluid lubricates and cools the pump. If the pump is allowed to run dry for a long period of time, it will overheat and need to be overhauled. You indicated the pump is pumping some and that is probably sufficient to protect the pump, but I would not feel right if I did not caution you a bit.

EDIT: I added some photos. The first is the hydraulic pump and PS pump on the engine. Those two top bolts should be tight and this fitting is the one I'd put a little oil around to see if it gets sucked into the pump because of an air leak. The 2nd photo has the rubber "T" just visible to the left side of th photo. The photo was taken from the left side of the tractor, but the T-boot is large and easy to see.

 

[J_J]

I agree with jinman on the suction air leak. If you have a suction leak, there would be plenty of air bubbles in the tank.

 

[gretchen8]

I have tried a couple of things and came up with this. If I drive it for a few minutes my bucket will stop working. I can stop and turn it off and crank it back up after 15-20 seconds and it work for a minute or so. I loosened the hydrostate filter, not the big hydraulic filter and it had pressure on it, cranked it up and the bucket worked again. I don't think its the pump. I will try replacing the filters, but it ran fine when it was parked 2 years ago. Of course when the bucket stops the hydrostate has problems working. It has to be something small and simple I am overlooking. Any ideas where to start. It could be a filter. Would it create build up in the lines just sitting?

 

[jinman]

What you are describing is exactly how the system would operate if it is sucking air into the system. When it sits, the oil can fill the lines and things seem to work normally for a short while. As soon as the lines empty and oil is being pumped, the suction draws in air from a leaking point and then you start having problems. The fact that the HST is acting funny as well as the loader means that the big main filter is leaking or the line I described to you with the big rubber "T" on it. Also, have you pulled your dipstick to see if you have enough oil in the reservoir? The dipstick is above the 3PH on the rear of the tractor, under the fuel tank. You can see a big yellow plastic fill cover on the left and on the right side there is a dipstick. Pull the dipstick and check the oil level while also looking at the oil for foaming.

Also, if the tractor sat for 2 years, there may have been something that settled/grew/or otherwise is partially blocking your main filter. The first step to difficulties like you are having is to check the level and condition of the fluid and then change all filters. That way you are troubleshooting with known good fluid and filters. It will cost a bit for new filters, but less than having someone come get the tractor or do onsite troubleshooting and repair.

 

[gretchen8]

All of the fluids are good with no bubbles or foam. Now the just hydrostat filter seemed to have some foam type oil in it, but not the main filter. I looked at the rubber T and it looked good with no indications of a leak.....now on the other side of the tractor I just noticed a leak on a rubber hose coming from the hydrostat filter going into what looks like a conector with wiring on it under your left foot. I will replace the hose and see if that is the problem. I agree with you....it does act like air is getting in the system, or preventing circulation of the fluid somehow. Pump is working when fluid gets in because the bucket will move. How do you get air out once I change the hose that is leaking? Thank you for your help!!

 

[jinman]

Gretchen, the pipe going from the HST filter to the connection that is on the left side with the electrical wires is on the output (pressure) side of the transmission charge pump. The charge pump in the HST transmission is a small pump that draws fluid from the reservoir and sends it under high pressure to the cooler in front of your radiator. After going through the cooler, fluid leaves and goes into the HST filter. When fluid leaves the filter, it splits into two paths. One path goes into the main HST transmission and the other one goes to that block under your left operator platform. The electrical wires run a solenoid controlled by the rabbit/turtle switch on the joystick and the one on the right fender (they do the same thing). The solenoid opens the valve to let fluid into the HST transmission to change speed. By the time fluid gets to this point it is under quite a bit of pressure and a small leak would NOT cause the kind of problem you are having.

When you checked the boot under the right side, did you attempt to tighten the clamps at all? I'm not talking a lot of tightening, but rather maybe 1/4 turn. Also, you should check the bolts at the top of the hydraulic pump and back where fluid comes out of the reservoir and goes into the filter. There is a small flange fitting with two bolts on the side of the transmission near the big filter. Check that those are tight.

There is a screen inside the reservoir where fluid comes out to the filter, but I have never heard of anyone having clogging problems on that screen on this model tractor. You would have to drain all the fluid to check this out and I'm pretty sure you don't want to do that. I still think you have a small air leak causing your problem. It could be a loose connection or even a cracked pipe. Air is normally not a problem to get out of the lines. I have removed hydraulic lines and filters and never had any problems getting the pump going again.

I'm including a diagram to help you. The fluid is drawn from the reservoir through the yellow colored line at #3 where suction from the pump draws it through the filter and out the big yellow tube. You can see where I colored the line going to the HST. At the "T" I didn't color the line going to the pump, but fluid is also drawn up to the main pump #4. The pink line shows fluid coming out of the charge pump and going to the cooler. From the cooler, I colored the line blue. You can see where it splits to the transmission and to the rabbit/turtle valve after going through the HST filter. Finally, the yellow line on top of the HST transmission (#1) is the return line to the reservoir.

 

[rkenne]

Did you ever get this problem fixed? Mine is doing the same thing now.