Toplink Hydraulic toplink question

[Tact]

I have a hydraulic toplink on my JD 4520. When I have a blade or rake on the back and I've adjusted the top link out to put pressure on the rear of the blade or rake I've noticed that as I go over the high areas of the ground the arm is being forced back into the cylinder. Almost like it hasn't enough pressure to keep the arm extended. It is normal? I would think not but I've never had a hydraulic top link before.

 

[Eric_Phillips]

I am no hydraulic expert but I would say you have a leak in the valve. I would try putting in a check valve.

 

[3RRL]

Agreed,
A double pilot operated check valve. (DPOCV)
Chances are your cylinder is good and your control valve is leaky. You don't have a "float" position on your valve, do you?

 

[IslandTractor]

This may be a stupid question but...Are you sure the hydraulic cylinder is being compressed? The 3PT hitch will naturally allow the whole implement to raise up when you go over a high spot but it would be surprising, even if there was a leaky valve, for the hydraulic toplink cylinder to compress so quickly just by traveling over a high spot. Remember you cannot really put down force on a back blade with a toplink, it just adjusts the angle of attack. Going over a high spot affects the 3PT but really shouldn't affect the toplink.

Sorry if this is totally obvious. I just cannot imagine seeing a hydraulic cylinder compress that easily or quickly even with a leaky valve.

 

[MJPetersen]

I was thinking exactly like IslandTractor. Are you sure that it is the toplink cylinder that is compressing? I know that there can be some leakage in the valve and the DPCV are absolutely great when that happens, and that Rob is a BIG fan of these little jewels, but there would have to be a huge amount of leakage to make the blade "float" like you described through the toplink. Now the 3pt is a totally different matter. It will float all the time because the cylinder there is only a one way cylinder.

Mike

 

[Tact]

No, it's the top link arm compressing back in the cylinder. Tomorrow, if the ground dries up enough, I'll work it again and double check.

 

[greg_g]

That's not necessarily the fault of the cylinder. Your tractors remote valve might be leaking/failing. Those pilot check valves don't really do much at all relative to the cylinder itself, they're more to compensate for problems with the tractor hydraulic remote system that feeds it.

But. If you disconnect the cylinder hoses from the tractor - and can still push the toplink rod back into the cylinder housing - it's a cylinder problem.

//greg//

 

[DK35vince]

My original hydraulic top link had no check valves and it did the same thing as Tact's cylinder is doing when using a boxblade and the blade got some weight/tension put on it. Made it very difficult to control the cutting depth of the boxblade effectively.
I replaced that cylinder with one with check valves and the problem dissapeared.

 

[Tact]

If it's a check valve problem, who would I contact to get a check valve installed?

 

[3RRL]

You might be able to get one from Mark at CCM, or at Surplus Center. I have both and I can tell you, the Surplus center Double Pilot Operated Check Valve is a lot bigger than the CCM one. That is what you need, a DPOCV, not just any check valve.

Do you have a hydraulic store in town? Maybe they have a source and can hook one up on your cylinder?