M Hydraulics

changed oil and now loader will not lift more than a foot. Have read through other ?.I changed from a 2 valve to 3 valve so i could have a outlet at the back of the tractor. When this didn't work i put on the old valve and it did the same thing. I think there is air in the system, what hose should i crack to get the most air out?

Before we tell you the wrong info, we need to know what type of cylinders are on the loader, including if the loader has a trip bucket, or controlled with hydraulics.
We also need to know if it is using a Liftall belly pump (not live) or a distributor driven live hydraulic system.
We further need to know if it has a reservoir added to the stock system. JimN

it has a belly pump,no other reservoirs,and cylinders for the bucket return.I'm not sure what kind of cylinders it has they are about 35" long and 2 1/2" shaft.

Then I would block up the loader so that all weight is on the bucket (On a plank or 4X4 or two), and the bucket cylinder is also not under load. I would remove one of the lift cylinders, and lay it so the hose connection is highest, and the cylinder is lower to the other end. Then I woule operate the lift lever to extend that cylinder. Then I would put it in the Lower position with the engine off, and manually push the cylinder in to its shortest length while keeping it low on the ram end (not past the shiny part of the ram, just to where it normally goes. I would do this several times, then check and refill the resivoir. Then I would reattach the first, and do it to the other side the same way. Again check the fluid level.
Re-attach and try it. I would also check the tilt cylinder for air in a similar manor, Both ends if needed. This is an open center system, and (I assume you wire back the main lift rod to use different spool valves) if you attach a third valve to the return hose going to the reservoir that must also be a open center valve with its return line attached to the reservoir. Good luck, air can be troublesome to remove. JimN