MCV ?

Is everything working okay? If so, stay the heck outta there.

MCV valves in the hydraulics are like carburetors are to gas engines. To some folks, these items seem to cause everything from earaches to the runs and more often than not, have absolutely nothing to do with either.

If you tractor is operating okay, leave things alone. You don't need to "check it".

Just my view,

Allan

It's on the left side right in front of the step, but only on larger 06, 56, 66, 86, and 88 series tractors. The tractors with the old mechanical TA do not have an MCV.

MCV means multiple control valve, or something like that. It's a valve that controls multiple things: steering, brakes, TA, and maybe even PTO.

May I recommend that you get the I&T service manual for the tractor, and read it? It assumes some level of mechanical ability, but even if you don't have any mechanical ability, it's better than being completely in the dark.

If tractor is full of hydraulic oil and the lift and PTO work then problem most likely is with MCV and pump. Could be that the key in MCV pump drive shaft is sheared / wallowed out or the pump drive shaft seal is worn and not sealing.
You really need to test the MCV pump and valve as directed by a shop manual. Will the hydraulic lift (two point or three-point)and auxilliary valves operate (lift a load)?
Does the PTO work properly (turn under load)?

If lift and PTO does not work ,then the PTO drive shaft splines are worn off also the splines in the clutch pressure plate which mate with the PTO drive shaft. The MCV pump is driven off of the PTO driven gear. If the splines are worn off of the PTO drive and pressure plate, it is my understanding that a tractor would have no steering ,brakes, TA or hydraulic lift and PTO.