OK, Geting closer on 806 brakes..more info

Start tractor, brakes lock up instantly. Still.
Disconnect return line from brake valve to return dump elbow, and routed with a hose from the brake valve to a pail. Started , brakes did not lock up. Tube from brake valve to that elbow that is screwed into top of transmission housing is NOT restricted, nor is the elbow. Fluid coming out of the valve is a almost frothy, actually looked like a 1/2 melted root beer float. I pulled the filter, filter has alot of slime on it,even some what appear to be white plastic chunks of some sort. I am now very doubtfull that that mechanic changed the fliud of filter, when he repaired an issue I had with 4th gear. So, I am apparently getting more volume to the brake valve than the brake valve can get rid of with out having enough excess volumn(very little pressure) to apply the brake piston. I am thinking I must have some thing going on with the flow divider, maybe some thing partially plugged. I plan on pulling the MCV off and inspecting. When I run a 1/2" hose from the brake valve to the fill hole and run the tractor the brakes worked as the should. Hook up the return line back to the elbow as it is supposed to be and the brake locks as soon as tractor is started. Any more advice as to next steps.

Notwithstanding the possible excess flow to the brake vale is there ANY possibility there's some sort of restriction in that return fitting/port?

Dave,

I have been following your troubles for some time but your last post triggered a thought in my mind. IIRC on an 856 I used to have there was a restrictor on the INPUT line to the brake valve. Should be similar on the 806. Might check into this. If that restrictor is missing, it could cause the excess flow you are seeing. HTH

That is what I figured would be the issue. I took a hose and blew into the housing through the return line. It would blow back at me(the line and the elbow are unrestricted), SO I took out the dipstick, and then it wouldnt blow back at me. I figured for sure then that if I ran it with the fill hole open,AKA dipstick removed, that just possibly the brakes would not lock up, but they did. Not instantly like when it is all routed as it should and with with dipstick in, but within a few second they slowly locked. When I ran a 1/2" hose from the brake valve and into the fill hole, then brakes did not lock up, BUT as stated oil was foamy coming out.
I beleive the brake is supposed to get 1 gpm flow, sure seemed like alot more than that, but maybe because it was foamy.

Putting a restrictor in the line might just do it, If there is supposed to be one. Other than that, the foaming issue could be associated with a bad Oring in the MCV pump. Over filling the tractor about 5 gallons would sure fix that. (standard operating procedure). But flow rates out of the brake valving should be sufficient (I remember it is a hybred tractor, and all parts might not have been used when it was reassembled. Jim