I am new to dealing with hydraulics but do not find the user manual very useful in this field - it doesn't deal with 50 year wear. I simply want to replace that pin to see if that is the fault but don't know which it is.
Help please
Position control pin
Position control pin
I have finally taken the hydraulic top off. The symptoms of a gradual deterioration in lift arms lifting at all at the time I investigated suggested a worn position control pin. But ... where is it?
I am new to dealing with hydraulics but do not find the user manual very useful in this field - it doesn't deal with 50 year wear. I simply want to replace that pin to see if that is the fault but don't know which it is.
Help please
I am new to dealing with hydraulics but do not find the user manual very useful in this field - it doesn't deal with 50 year wear. I simply want to replace that pin to see if that is the fault but don't know which it is.
Help please
Re: Position control pin
Find the cross shaft that goes through the cover, the one the lift arms attach to. In the center is an arm that the lift cylinder pushes on via a large round rod. On one side of this arm (called a 'ram arm' in the parts book) is a cam. The cam is cast is one piece with the arm......the position control pin rubs against this cam. The pin is pressed into the 'control valve actuating lever'.
Jack
Re: Position control pin
Commander that was all I needed thank you. I have found it and seen it - the cam is rough and seems a little corroded although everything else is covered in grease. The pin is about half worn through so the symptoms correctly diagnosed the problem.
Next question though - can the pin be replaced in situ? I can get enough space to drift it out but wonder if that's a safe option.
Next question though - can the pin be replaced in situ? I can get enough space to drift it out but wonder if that's a safe option.
Re: Position control pin
I don't think doing it in place will be a problem. Get a mate to hold something heavy (steel bar, hammer etc) against the back of the arm as close to the pin as possible to take the impact. I replaced mine with a short length of drill shank.
Peter
Peter
Re: Position control pin
Is it the same diameter throughout? It's easier to drift from outside in in that it may break given how worn it is from the inside out. But the bracing from outside in is in danger of being one of the mechanism springs.
Re: Position control pin
Couldn't drift it out so as a tempo measure I've taken up the adjustment on the turnbuckle. Contact is now made but on reassembly I still have no lift. Apart from standing for a long time, nothing els has changed. Why won't it lift? 
Re: Position control pin
Instructions for doing all the linkage adjustments can be found in the wiki on this site, along with some troubleshooting info..
No lift can be caused by a number of things....a common reason is a sticking (stuck) unload valve in the valve chest. The unload valve is between the lift cylinder and the control valve, in a bore in the casting, behind a plug. (hint look at the wiki article mentioned above)....this valve was fitted with an o-ring seal at the factory. The o-ring swells over the years and causes the valve to stick....sludge can accumulate in the bore also. Your comment about the lift getting gradually worse over the years also points to this being a suspect.
Other possible causes....bad seals in pump or pump unloader (pressure pop-off) stuck open (usually will still lift with no weight), oil diverted to aux port (control in 'aux' position), broken linkage, etc , intake screen completely clogged, cotter key on pump gear sheared.....
I would say that it is unusual for the pump to completely quit, they tend to get a little weak over the years, but generally don't just die.
I suspect you are looking at removing the cover again
and stripping down the lift cylinder/valve chest. While you're in there, replace the position control pin,inspect the linkage, fit new seals everywhere, clean the suction screen.
No lift can be caused by a number of things....a common reason is a sticking (stuck) unload valve in the valve chest. The unload valve is between the lift cylinder and the control valve, in a bore in the casting, behind a plug. (hint look at the wiki article mentioned above)....this valve was fitted with an o-ring seal at the factory. The o-ring swells over the years and causes the valve to stick....sludge can accumulate in the bore also. Your comment about the lift getting gradually worse over the years also points to this being a suspect.
Other possible causes....bad seals in pump or pump unloader (pressure pop-off) stuck open (usually will still lift with no weight), oil diverted to aux port (control in 'aux' position), broken linkage, etc , intake screen completely clogged, cotter key on pump gear sheared.....
I would say that it is unusual for the pump to completely quit, they tend to get a little weak over the years, but generally don't just die.
I suspect you are looking at removing the cover again
and stripping down the lift cylinder/valve chest. While you're in there, replace the position control pin,inspect the linkage, fit new seals everywhere, clean the suction screen.Jack
Re: Position control pin
Tku Commander
Last year whil gang mowing, an hours work and bouncing around suddenly brought the lift to life and it gave a swan neck to the gangs! That seems consistent with a stuck unload valve. Why was there an O ring in the first place if it's not necessary?
Rob
Last year whil gang mowing, an hours work and bouncing around suddenly brought the lift to life and it gave a swan neck to the gangs! That seems consistent with a stuck unload valve. Why was there an O ring in the first place if it's not necessary?
Rob
Re: Position control pin
I was looking for Stefan's site for more piccies but it's gone!
Re: Position control pin
Well, we would have to find the engineer that designed the thing to be sureroromac wrote:Tku Commander
......... Why was there an O ring in the first place if it's not necessary?
Rob
, but I suspect it was a cost saving measure.. Later versions went to a metal 'seal' similar to a piston ring. Probably had some ''negative feedback' from the field. Many people just leave the o-ring out when they overhaul one and report the lift works good enough without it. If you do replace it, go to a CNH dealer and order the correct one. They should still be available. This is not a place where you want a cheap one that may not fit just right, or will quickly swell again.
Jack