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.
This post was edited by Owen Aaland at 21:18:08 05/11/11.
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Today's Featured Article - Grain Threshing in the Early 40's - by Jerry D. Coleman. How many of you can sit there and say that you have plowed with a mule? Well I would say not many, but maybe a few. This story is about the day my Grandfather Brown (true name) decided along with my parents to purchase a new Ford tractor. It wasn't really new except to us. The year was about 1967 and my father found a good used Ford 601 tractor to use on the farm instead of "Bob", our old mule. Now my grandfather had had this mule since the mid 40's and he was getting some age on him. S
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