Koyker 210 loader problems

[Fergster]

I have a koyker loader on my 261 that will stop operating most of the time when you switch the selector valve thats bolted to the top hyd cover to 3 point and then back to loader. The 3 pount lift allways works when switched to that position. Normally when you move the switch arm you can feel hydraulic resistance and hear the bypass valve cycling. When the loader stops working the valve moves easily with no resistance (theres no pressure) .its nothing to do with the tractor because the lift works fine. If you let it sit it works again and as long as you leave it in loader position it never screws up. My guess is the bypass or safety valve in the loader hyd position control is sticking open allowing the fluid just to loop back to the sump. Either that or the selector switch is somehow being intermittently blocked by a piece of debris. I havent started on it yet. Thought i would see if anyone has an idea