Anyone replaced/simplified Selectamatic hydraulics?

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cossyrec
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Location: East Yorks

Re: Anyone replaced/simplified Selectamatic hydraulics?

Post by cossyrec » Sat Oct 21, 2017 9:23 am

when you remove the casting with four bolts in there are two o rings the feed to the ram cylinder which either falls out or sticks to the casting the other is around a pipe. its is this pipe that needs blocking. I used a piece of nylon made into a top hat shape. I forget dimensions but fattest part was just a thou or two smaller than O/D of pipe and about 3/16 thick thin part was around 3/4 inch long and snug fit in pipe. gentle tap into pipe. reassemble making sure both o rings are in place. Hope this makes clearer. Did mention plug in previous post

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skyrydr2
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Re: Anyone replaced/simplified Selectamatic hydraulics?

Post by skyrydr2 » Sat Oct 21, 2017 1:24 pm

Is there any way you could tap the cover port and plug it with a socket head plug so it will be flush so it doesnt affect the seal on the other port.
What is happening is your high preasure oil is just returning to the resivoir through rhat pipe.

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ollek
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Re: Anyone replaced/simplified Selectamatic hydraulics?

Post by ollek » Sat Oct 21, 2017 3:20 pm

The easiest and by far the best way is to plug the pipe in the way cossyrec has been advising. Doing it in this way will also make it possible to easily convert back to the original setup.

880Aubrey
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Re: Anyone replaced/simplified Selectamatic hydraulics?

Post by 880Aubrey » Mon Oct 23, 2017 1:43 pm

Will be fitting the plug this week. Looking back through I do see where Cossyrec did mention the plug.

Thanks Again,

880Aubrey
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Re: Anyone replaced/simplified Selectamatic hydraulics?

Post by 880Aubrey » Tue Jun 05, 2018 1:27 pm

**UPDATE** I finally fitted the plug and just as advertised.....the 3pt lift works!!! The Selectamatic valve is successfully bypassed with the double Cessna valve now operating the 3pt lift.

Thanks to all who contributed.

Now this did reveal another problem. The hydraulics are very weak, not able to fully lift a 5' rotary mower at full throttle . I connected a gauge to the cessna valve and at full throttle it would only reach 400psi on one line and less on the second one.

How should I attack this, start at the cessna valve and work my way to the pump or start at the pump and work my way to the cessna valve?
(currently running new Traveller Heavy Duty SAE30 oil in the gear box with a new filter)

cossyrec
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Re: Anyone replaced/simplified Selectamatic hydraulics?

Post by cossyrec » Wed Jun 06, 2018 3:59 pm

I don't know how the Cessna valve works but if it completely bypasses the selectematic block if so it must have a relief valve somewhere. hence maybe worth giving it a tweak see if it makes a difference or stripping to see if its sealing correctly.

880Aubrey
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Location: USA

Re: Anyone replaced/simplified Selectamatic hydraulics?

Post by 880Aubrey » Wed Jun 06, 2018 4:19 pm

Thanks Cossyrec, I think I am going to delete the original cessna valve and add a modern spool valve like you have. If that doesn't improve the the 3pt lift I will then find the relief valve.

Even though I still have an issue to work through, Seeing the lift move is a huge motivation!

Gard
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Re: Anyone replaced/simplified Selectamatic hydraulics?

Post by Gard » Wed Jun 06, 2018 5:03 pm

I don't know either, does the Cessna valve completely bypass the selectamatic valve system? In other words if the selectamatic lift or hold valve were leaking could that be the reason for the low pressure?

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ollek
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Re: Anyone replaced/simplified Selectamatic hydraulics?

Post by ollek » Wed Jun 06, 2018 6:11 pm

The original Cessna valve bolted on top of the rear axle is the first one after the pump and the flow goes from the Cessna valve neutral port to the Selectamatic valve chest. There is no need to plug anything if the original Cessna valve is used, just connect one of the outlets from the valve to the lift cylinder and the other to the tractor transmission lubricating gallery. Plugging the pressure pipe under the Cessna valve base plate will lead to the pump working on maximum pressure all the time. A low pressure from the Cessna valve is because the pressure relief valve on top of the pump is damaged, the pump is gone, the O-rings on the pressure pipe from the pump are damaged or the pipe is damaged. The pressure to the Selectamatic valve chest will be the same as the one from the Cessna valve.

cossyrec
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Re: Anyone replaced/simplified Selectamatic hydraulics?

Post by cossyrec » Wed Jun 06, 2018 9:20 pm

When I said relief valve I did not mean on the control chest but on the Cessna valve. Indeed have had a look at photos and it does appear to have one slim chance but this could be the problem

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ollek
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Re: Anyone replaced/simplified Selectamatic hydraulics?

Post by ollek » Thu Jun 07, 2018 4:30 am

There is no pressure relief valve in the original Cessna valve. The relief valve for the hydraulic pressure is on top of the pump, inside the pto housing. The valve at the top of the valve chest is a shock valve that opens only if there is a sudden pressure increase in the lift cylinder. This will happen only if the tractor is driven in high speed with a heavy implement connected to the lower links.

cossyrec
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Re: Anyone replaced/simplified Selectamatic hydraulics?

Post by cossyrec » Thu Jun 21, 2018 11:12 pm

sorry for delay replying. I think before stripping out back end pump I would completely rule out Cessna valve bearing in mind you seem intent on fitting modern day spool bank. to do this I would try and remove Cessna valve and and fit a camels hump failing to find one I have some sketches of what I was going to knock up to make the equivalent.

880Aubrey
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Re: Anyone replaced/simplified Selectamatic hydraulics?

Post by 880Aubrey » Tue Jun 26, 2018 12:32 pm

Thanks Cossyrec, Would you mind sharing your sketch? I cannot find an original camel hump anywhere.

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ollek
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Re: Anyone replaced/simplified Selectamatic hydraulics?

Post by ollek » Tue Jun 26, 2018 1:26 pm

I can not understand why you wold replace the Cessna valve with a camels hump. The Cessna valve setup with the bottom slice, Cessna spool valve and top cover is working exactly in the same way as the camels hump. The pressure to the Cessna valve (and to the camels hump if there is one), is coming straight from the pump and if the pressure is low or there is no pressure, then the problem is in the pump, pressure relief valve or pipe from pump to Cessna valve (or to the camels hump). If you need to fit several external spool valves, then you just connect the pressure and return ports of the extra external spool valves to the Cessna valve pressure and return connections and lock the Cessna valve control lever in operating position for the time you need to use the extra spool valves. If all the functions you need are independent of the Selectamatic valve chest, then you can leave the Cessna valve lever locked in for operation all the time. Please be aware that all tractors exported to the US had the Cessna valve as standard, and no camels hump. A camels hump is not needed if the tractor has one or several Cessna valve(s). Cossyrec, giving information's about a camels hump will not help a US tractor owner, there are no tractors with a camels hump in the states.

cossyrec
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Re: Anyone replaced/simplified Selectamatic hydraulics?

Post by cossyrec » Fri Jun 29, 2018 10:24 pm

Reason I suggest removing Cessna valve is to rule out internal leaks to return pipe plus it could be put up for sale if required iam working on putting on sketches but struggling please bear with me

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