706 mcv?

I bought the tractor with no steering hoping it just needed some mcv attention. I have tried priming multiple times and been unsuccessful so I ordered a manual and a mcv rebuild kit and am looking for a pump. But this morning I had someone question if that was the problem because the loader was working when the steering stopped even after steering was completely lost the loader was still working just very slow and sluggish and the oil light stays on steady now. Could I have another problem?

Yea ya could .Have you changed the hyd. filter ??? what does the oil look like ?? Do you have brakes?? And since i can not check the tractor out or run a flow rate test there are a lot of it could be tis or it could be that or maybe it is this .

Oil looks good getting new filter tomorrow, the right brake seems to work a little but nothing on the left side.

I don't have any kind of gauges or anything to do pressure or flow test with and I know next to nothing about this tractor I'm just trying to avoid taking it to the dealer and spending a fortune. But maybe I will hold off on buying the pump until I get more of an idea whats going on.

Just tried it again the right brake is working and after throttling it up pretty good and a lot of turns of the wheel I was able to get some steering but very little and it took maybe 6 turns to gets the wheels to move either way and it slow go when they did start moving.

Did you check the obvious thing first, the fluid level.
Got the same problem with the one here. Rebuilt the MCV in fall when the TA was replaced. Worked good till it got cold, now it works some when warmed up. Not sure if a o-ring isn't set right or what. I did dump a few gallons of fluid in when it was warmer from running, but didn't try it cold yet.

Over fill it by 5 gallons. it costs little hurts nothing and just might make it work. A common issue is sucking air. The extra Hytran covers the usual intake leak. Jim

I overfilled by 2.5 gallons it was all I had at the time I will pick up 2.5 more when I get my filter tomorrow.

2.5 more gallons of hytran new filter clean screen. Now after working the wheel back and forth and throttling up pretty good I've got better steering than before but still not good at all. How can I narrow this down between mcv valve, pump, hand pump, and anything else in the system that could be causing this?

Your tractor has two separate hydraulic systems other than sharing a common filter. The rear pump furnishes oil for the hitch and auxiliary valves. That system is continuing to function even when you have no steering.

The front pump is located on the inside of the MCV. That pump provides oil for the steering, cooling, brakes, TA control, and lubrication.

The flow from the MCV pump goes first to a flow divider valve and a 3 gpm orifice. The 3 gpm has priority so that flow is maintained unless the pump is not able to supply that much. The pump is rated at 9 gpm at rated engine speed. Any flow in excess of the 3 gpm goes to the oil cooler in front on the radiator and then returns to the MCV. There is a regulating valve to limit the pressure in the oil cooler to about 60 psi. This return flow is then routed to the rear end to provide lube for the reverse idler shaft, ring and pinion gears, and the range transmission main shaft.

The 3 gpm is routed to the steering control valve on top of the center section where it is available for use by the steering system. From the steering control valve the flow is routed back to the MCV. The steering pressure is regulated for maximum pressure by the steering relief valve. If the pressure exceeds the relief valve opening pressure the flow passes through the valve and is routed to the same channel as the oil returning from the steering control valve. There is also a steering check valve located in this channel that is normally closed. Its only function is to allow oil to be drawn into the steering system if the pump is not supplying the necessary oil flow. This allows for manual steering.

The returning oil from the steering next goes to the brakes where there is a 1 gpm orifice in the inlet fitting of the brake valve. On the 06 series tractors this is a 1 gpm flow through the brake valve whether or not the brakes are being used. On later tractors the brake valve was changed to a closed center valve so that the 1 gpm flow is only lost from the system while then brakes are being applied. After the brake system is supplied with oil the remaining 2 gpm is used for the TA control and TA lubrication. Once the oil has reentered the MCV from the steering control valve it is regulated to about 245 - 265 psi by the pressure regulating valve. The flow bypassing the pressure regulator valve is then sent to the TA lube circuit where it is regulated to about 20 - 22 psi by the lube circuit pressure regulator valve. Oil that bypasses the TA lube regulator valve is dumped to the reservoir. When the clutch pedal is depressed all of the TA pressure is dumped to the reservoir to release the TA clutches and stop the TA lube flow to eliminate drag caused by the lube circuit.

To narrow down the possibilities of what the problem may be, you said your steering was still poor. When driving the tractor with the TA lever in the direct (forward) position turn the steering full left or right so that the relief valve open. You should be able to hear the valve squeal when it opens. If the TA does not downshift the problem is most likely the steering relief valve, usually a blown O-ring. It could also be a problem with the steering hand pump or the cylinder in the front bolster but that would be rare. compared to the other areas. If the TA does downshift you are losing flow to the brakes and TA. If the problem is sever enough you may not get the relief valve to open. This could be a worn out pump, blown O-rings, or a sticking flow divider valve. I normally just remove the MCV and visually inspect everything. If the valves and O-rings are all OK then I replace the pump.

You could also have problems with leakage inside the TA but that is something you will need to uses pressure gauges to determine. Since your problem shows up in the steering the problem is in the oil flow before the TA.

I realized after my last post I didn't try bleeding air from system again after changing filter. I went out pulled the 5/8 plug took a hytran shower and now I have great steering. Still did what you suggested mark and everything checked out. But with the ta back if you turn full lock either way the tractor all but stops. This doesn't worry me to much because I only use the tractor for moving hay, snow, and other small jobs but I am curious as to what would cause this.