low TC Hydraulic Pressure

Sun Oct 06, 2013 9:09 pm

I certainly would appreciate any suggestions...

This afternoon I was replacing a hose to a log splitter that I have used many times in years past - it is connected to the regular touch control on my 48 cub.

With the large touch control filler plug removed, with the engine at idle speed, I slowly worked the log splitter piston back and forth using its own hydraulic valve and added hydraulic fluid to the touch control to get the air out of the new hose. At one point, the TC "burped" and shot some hydraulic fluid out. with the log splitter piston all the way retracted, I put the TC filler plug back in. To test things I put a log on the splitter, cranked up the engine to full speed, and found that I had almost no pressure. At that point, I tried to use the TC to lift the belly mower. The TC would only lift the belly mower if I had the engine running at top speed. Normally, the TC would lift and drop the mower even at slow idle. I am guessing that the gears are still on the pump because I am getting some pressure.

Did I cause a seal or something in the TC to pop out by running the TC without the plug in it?

BTW, I mowed about 1/2 acre after this happened thinking that some air might still be in the system. No luck - TC will not lift the belly mower unless at full speed.

I did rebuild the TC when I got this one used about 5 years ago. I have never had a problem like this.

Thanks in advance for your suggestions Cub brain trust :worthy:

Rick

Re: low TC Hydraulic Pressure

Sun Oct 06, 2013 10:01 pm

Try adding more hydraulic fluid to the reservoir and slowly continue cycling the log splitter cylinder and mower deck. Thinking still more air in the system.

How is external hydraulic system plumbed? Leak in one of the control valves - ??

Re: low TC Hydraulic Pressure

Mon Oct 07, 2013 5:34 am

Having the plug out on the TC would not damage the system. It is something else that is causing the slow hydraulic action.

Re: low TC Hydraulic Pressure

Mon Oct 07, 2013 12:48 pm

I have a guess, and it's just that, a guess. What I'm about to suggest shouldn't happen under normal circumstances. I'm guessing while you were cycling your log splitter you may have accidentally continued to try to retract the cylinder momentarily and put some excessive strain on the system. While this happens somewhat routinely with no ill effects, especially with log splitters, I suggest, even though the tractor was idling, your system had an O-ring or something in your tractors touch control ready to fail anyway. The straw that broke the camels back - so to speak. I know, no real help. It sounds like your pump is still working but your system is leaking/bypassing internally.
Eugene wrote:Try adding more hydraulic fluid to the reservoir and slowly continue cycling the log splitter cylinder and mower deck. Thinking still more air in the system.

How is external hydraulic system plumbed? Leak in one of the control valves - ??


Expanding on Eugene's thoughts, after you've added the oil look for external leaks and check to see if it's leaking oil into the engine (through the pump). If it's not air in the system and not leaking externally then it must be bypassing internally, through a seal or pressure relief valve. Hydraulic oil under pressure, like electricity, will take the path of least resistance.

Re: low TC Hydraulic Pressure

Mon Oct 07, 2013 1:02 pm

Thanks Ray - that was my guess as well. I am using a regular log splitter valve. At one point I may have allowed the "automatic return to neutral" function do its thing. I need to keep holding to handle to split the wood, but I can reverse the handle to the point it will stay there by itself for automatic return. I wonder why reverse/return motion of the splitter cylinder would cause this to happen instead of the extension/wood splitting motion?

I have a 3" by 22" splitter cylinder. Since the 1" shaft of this cylinder certainly takes up some volume within the bath of hydraulic fluid, I wonder if I should put a vent (drill a small hole) in the TC reservoir to release air pressure or if the heavy TC cast iron block can easily take this pressure? Like I said in my earlier message, I have used this splitter on multiple occasions to cut small amounts of large pieces of wood without any issues.

One more item. I run one hydraulic line directly from the high pressure side of the TC - and the return line to the low pressure valve block I bolted against the TC. What I found is that that is really not a low pressure line because I blew out an spin-on hydraulic oil filter on that line.

I will visit IH dealer and pick up a new kit. But boy - it would be wonderful if an air bubble popped out this week for full hydraulic power so I would not have to remove and rebuild that unit again :-:-):

Re: low TC Hydraulic Pressure

Mon Oct 07, 2013 2:53 pm

rick 48 cub wrote: I wonder why reverse/return motion of the splitter cylinder would cause this to happen instead of the extension/wood splitting motion?

Normally it wouldn't make any difference - in or out. As far as the tractors hydraulics is concerned - pressure is pressure.

rick 48 cub wrote: I wonder if I should put a vent (drill a small hole) in the TC reservoir to release air pressure or if the heavy TC cast iron block can easily take this pressure?

I wouldn't do that. The 1" shaft in your cylinder takes up a touch over 17 cubic inches which translates to a bit more than a half pint. The "back pressure" should be minimal. I would install a small external reservoir, a quart or so, and plumb it into the fill port on the touch control. If your blowing out a filter on your return line then something else is going on, there shouldn't be that much pressure. The filter will handle some pressure, at least 100 psi or so, I've read somewhere that they will handle more than that, maybe 200 to 300psi.

Are you using a TC bypass block (it looks like you may be)? The high pressure side will definitely blow out a filter, a Cub can develop 1500 psi. Since your splitter return line goes back to the TC perhaps the way it's plumbed is causing the pressure when the TC is activated. The pressure will spike in that "return" line, in effect making it become a pressure line. Without seeing it this is still pretty much a guess.

Here's a link to some posts about splitters and bypass blocks. This should help although it doesn't solve the loss of power in your hydraulics.
viewtopic.php?f=171&t=70030&p=567678&hilit=bypass+block#p569545

rick 48 cub wrote:it would be wonderful if an air bubble popped out this week for full hydraulic power so I would not have to remove and rebuild that unit again
That would be great, I hope that's all it is, pumps have been known to cavitate.

Re: low TC Hydraulic Pressure

Mon Oct 07, 2013 3:08 pm

Rick:

You may not have to rebuild that pump/reservoir at all. That precise thing happened to me during my Splitter Project. When you burped the system and the TC Fluid shot out, it caused the level to drop. Add some more TC Fluid and you should have your full range of motion restored. BTDT.. and yup, it was mighty :oops: ing....

I would also make sure that your supply and return lines are connected properly. And no .. you may not ask why I know that :big give up: ... A lot :big shy:


The solution I found to be the most reliable was to add a pony tank/hydraulic fluid reservoir.

Image

Image

Re: low TC Hydraulic Pressure

Wed Oct 09, 2013 11:23 am

If you are using a regular TC bypass block, then the pump discharge should be going directly to you splitter valve. When the splitter valve is in the center position it will be open to return, which in this case is the pressure side of the TC block. When you move the splitter valve in the "split" direction, all of the fluid should be directed to the extend side of the cylinder, and the relief valve on the splitter valve should regulate pressure. If you are not getting pressure to the splitter cylinder, then either the pump is not producing any pressure, or the relief valve on the splitter cylinder is open and fluid is passing straight through to the TC.

If you are not getting enough pressure to operate the TC, then that would indicate that either the pump is not making any pressure, or there is a problem with the relief valve, or the TC positioning valve.

I guess what I'm trying to say is that a problem with the TC block should not cause your splitter to lose pressure, as the oil is not going to the TC unit at all when the splitter valve is operated, until the pressure in the cylinder reaches the relief setpoint of the splitter valve. If you can't get pressure to either hydraulic system, then I would guess that there is a problem with the pump, or you have a lot of air somewhere in the system.

Have you ever adjusted the relief valve on the splitter valve assembly? I can't remember exactly what the maximum operating pressure for the hydraulic pump is, but I remember that it is low by hydraulic standards. I'm sure one of the experts will chime in with a number. If the relief valve on the log splitter valve is set at a pressure higher than the pump can produce, then you could have damaged the pump by holding the splitter valve. I don't know what the weak link on the Cub hydraulic pump is, but I'm sure that more than one person on this forum has found out. It could be as simple as a blown seal.

Anywho, I hope this reply isn't too rambling and confusing. Long story short, I think that you either have a pump problem, or two different problems, one in each valve system.

glenn

Re: low TC Hydraulic Pressure

Wed Oct 09, 2013 11:42 am

Firing up my home built log splitter with Kohler engine powered hydraulic pump for the first time. Hydraulic pump whipped air and hydraulic fluid into a froth. Froth boiled out of the reservoir. Let system set over night for air to bleed out of the froth. Worked fine since.

Re: low TC Hydraulic Pressure

Wed Oct 09, 2013 11:45 am

I hope that frothy fluid is my only problem!