a little more info, but still no unlocked brakes 806

OK, Measuring the pressure at the port at the rear bottem of the MCV where the orifice is. I have about 1500# max pressure when you are turning the steering wheel. Disconncting a power steering line mid point, we had about 1 gallon flow in about a minute turning the wheel one way, and probably close to 5-6 gallons if turned the other way. The gauge we used was a 3000# gauge. We connected the gauge to the port on the brake valve that goes to the right brake, started tractor and it did not seem to really make any noticeable pressure on this gauge, but yet the brakes locked up. How much pressure does it take to apply the brakes so they lock like this? We took the pressure regulator off another tractor and tried it in this one and there was no change. Please note, that when you start the tractor, there is SO MUCH pressure on the brake pedals that you can barely push the brake pedal a half inch. Please recall that this brake valve was tried on another tractor and worked fine after it had been rebuilt. I can not find anything in the IT manual about how many GPM flow should be to the brake valve from the MCV? I did replace ALL 8 return springs in the brake covers. If the return(dump) line from the brake valve is open all the way to where it goes into the tractor transmission housing, is there anything that could be restricitng the dump flow after that? This is so frustrating, every one seems stumped. Pulled the flow control valve last night again, wondering if that should be replaced or swapped.

Take the return line off of the brake valve. Attach a length of hydraulic hose to the fitting on the valve and insert the other end into the hydraulic oil fill port and SECURE it so it can't possibly come out and spray oil/hurt someone. See if the system now works as intended.

If so, you'll need to figure out what is restricting the return line or the port where it dumps.

Thanks bob. I will try that.

Any luck?

I think I have an official IH Blue Ribbon hydraulic manual that would cover that tractor. I intended to look today at the shop but my REAL job kept me too busy.

If you haven't solve this, I'll try to find it.

You should never have more than 3 GPM flow in the steering circuit.

Oil flow in the MCV circuit of an 806 comes from a 9 GPM pump at rated speed. Flow from the pump goes first to a priority flow divider valve with a 3 GPM orifice. The 3 GPM is directed to the steering and that flow should remain constant through the entire RPM range of the engine. The rest of the oil flow goes to the oil cooler in front of the radiator and then returns back through the MCV assemble and out to lube the range transmission and differential. This flow can range from nearly no flow to about 7 GPM at high idle speed.

The 3 GPM flow goes to the steering and then returns to then MCV assembly. If the steering pressure exceeds the relief valve setting the oil will bypass the valve in the MCV and join the return flow from the steering. This 3 GPM return flow is channeled next to the MCV pressure regulator valve to maintain a pressure of about 240 PSI. This flow is then used to provide pressure to the brakes and TA controls on tractors equipped with TAs. When the oil leaves the MCV it passes a check valve on the way to the brake valve. There is a 1 GPM orifice at the inlet fitting to the brake valve. The brake valve on the 806 is an open center type valve and so there is always a 1 GPM flow though that valve whether the bakes are applied or released. Later tractors used a closed center valve and they flow the 1 GPM only when applying the brakes.