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Harry Ferguson Tractors Discussion Forum
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Detailed TO-30 Hydraulic Rebuild Questions

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Shane

07-23-2003 06:45:42




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OK, guys. My dad and I have decided to rebuild the hydraulic pump and components in our TO-30. He is an old tractor mechanic, and knows how to rebuild them, but we are trying to better understand the operation so we can find our problem. With an implement attached, the lift will fall in about 15 seconds with the engine turned off. We would like to improve this, as it is causing some problems with operation of the lift.

Well, when we tore the pump apart, we noticed the e-clip had fallen out of the control valve. Does anyone know why the control valve rotates back and forth in it's bore? It is just to keep it from freezing up? Could this missing e-clip have caused the control valve to work improperly?

Also, what is the function of the relief valve? Should it leak significant amounts of oil out the small holes in its periphery? When we put compressed air (about 100 psi) into the pressure port, and close everything off, the pressure leaks around the relief valve. Is this normal?

Also, what exactly can go wrong with the control valve? I know it is common practice to replace these, but why? If it fits tightly in the bore, will it be OK? Ours seems to fit snugly in the bore, without too much wear. What exactly is the function of the poppet needle inside the control valve?

How critical is the condition of the piston and rings? Ours have a few scores in them, but don't seem to be leaking much oil at all. In fact, when we looked inside the side cover, we saw no oil coming from the piston. Should I still replace these, or is it a waste of money?

Any other tidbits regarding the operation of this system, especially the operation of the control valve, would be appreciated. Also, I have lookied online at the FOF website and the Holland website. Any other good explanations of this system?

Sorry for all the questions. :)

Thanks again.

Shane

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Andy Dunford

07-24-2003 00:52:03




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 Re: Detailed TO-30 Hydraulic Rebuild Questions in reply to Shane, 07-23-2003 06:45:42  
john uk send me the the exploded views of the to 30 system as i am soon to encounter one of these lifts as it knock and lets down fast when cut tractor off? jdunford@sowega.net



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john(UK)

07-23-2003 11:32:38




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 Re: Detailed TO-30 Hydraulic Rebuild Questions in reply to Shane, 07-23-2003 06:45:42  
The time for the hydraulic to fully lower should be at least 4 mins, less than that will not do. Some hydraulics will hold up for days others half hour or so.The control valve oscillates in its bore to stop it sticking under load, it is possible that the "e" clip beng loose caused the control valve not to oscillate and therefore stick, but we sometimes got trouble with the valve and oscillator and we have on occasions removed the oscillator altogether.The relief valve is there for safety, so the hydraulic pressure will not rise above the designed pressure (2000psi). The valve should not leak at all under this pressure, but obviously using air to test it is not quite the same as oil so the readings will be different because the air will escape more easily than the oil, so really you need to test it under hydraulic pressure, but from what you say it appears it requires replacing anyway. The control valve is quite simple, the only thing that can go wrong really is wear, which will produce ridges along the valve itself or the control valve bush in the pump body, if there are any ridges at all there is a possibility of it sticking when under load. The poppet as you call it in the control valve, I take it you mean the stem that is in the valve one end and has the cross-piece that goes onto the control fork at the other? well all that does is allow some flexibilty in the valve linkage should it get stuck, if it sticks and you move the quadrant lever it loads that spring up so more pressure is applied to try to move the control valve and so you stand a better chance of freeing it. Originally the control valve did not have an oscillator fitted, it was introduced later to stop the valve sticking when worn. The condition of the piston and rings isnt that critical, just remove the rings from the piston and check them in the bore of the cylinder at both the unworn part and in the worn part and see what the gap is..if its more than 1/8" they are worn, when you rebuild the piston, make sure the rings gaps are evenly spaced around the piston. To check if the wear is ok on the piston and ram cylinder all you have to do is observe the amount of oil leaking from the end of the cylinder when its under load, if it drips its fine, no running stream tho. Both the sites you have looked at are good and you should have all the info you need from them. If you would like the exploded views of the hydraulic pump and the lift cover just let me have an address I can email them to.

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Shane

07-23-2003 12:15:37




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 Re: Re: Detailed TO-30 Hydraulic Rebuild Questions in reply to john(UK), 07-23-2003 11:32:38  
shane.schmidt@midwesttowers.com

Great info. I really appreciate it. Already ordered the relief valve, so hopefully that will fix my problem.

Thanks,
Shane



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David UK

07-23-2003 08:11:16




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 Re: Detailed TO-30 Hydraulic Rebuild Questions in reply to Shane, 07-23-2003 06:45:42  
I need to do the same job on my FE35 as it leaks down really fast too. I don't think you should be seeing any leakage at the relief valve. Its setting is about 2500psi so it shouln't leak at 100. I gather that control valve is arranged to turn to stop it sticking.

My understanding (which may be wrong or incomplete) is that leakage is possible from 5 places. Lift cylinder, supply pipe and seals, pump valves, control valve and relief valve.

My guess has been that, in my case, my hydraulics are probably falling because oil is escaping via either leaky pump valves or via the control valve or probably both. I think this because I can no sign of leakage at cylinder or any oil disturbance to suggest relief valve is blowing off. I would think that if pump pistons were worn this might affect the oil delivery volume and pressure but wouldn't cause leakdown.

I haven't opened it up yet but will be interested in what your question produces by way of response.

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john(UK)

07-23-2003 11:48:45




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 Re: Re: Detailed TO-30 Hydraulic Rebuild Questions in reply to David UK, 07-23-2003 08:11:16  
The pump used on your FE35 is a different beast to the TE/TO tractor. If you can't spot any leaks like you say I would think its the pump valves that are causing the problem, unlike the TE/TO pump it doesnt have the extra check valve to keep the pressure off the pump and its all carried on the valves in the side chambers and with the extra hydraulic pressure they have to cope with they can wear. Most unlikely its a leak on the control valve usually the only problem you get with the control valve is it sticks when worn. Any wear on the pump pistons would have to be excessive to stop it building up its normal working pressure and I think you would have had some evidence of problems other than it dropping rather quickly. One of the symptoms of wear on pistons is jerky lifting....only thing to do is remove the pump and look. If you require exploded views of the pump and the rest of the hydraulics, let me have an email address I can send them to.

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David UK

07-23-2003 13:48:57




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 Re: Re: Re: Detailed TO-30 Hydraulic Rebuild Quest in reply to john(UK), 07-23-2003 11:48:45  
Thanks John. I was thinking TO35 was similar to my 35. I would find diagrams useful. Address is d (dot) mclean (at) ntlworld (dot) com. Sorry about format but it may help to avoid some spam. Is there a possibilty that my problem could be down to the draft sensing system being stuck? It occurs to me that when I had the spring that the top link attaches to out during my rebuild, the rod that it operates against seemed to be solid, with no noticeable movement. If it were stuck in the "lower links" position could that be causing it to have trouble lifting weight and drop quickly?

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