My dad has a david brown 990 selectamatic, i was try to help him pull blades off the bush hog when we maxed out the three point hitch going up, now it does not want to go down. IT seems like it is air lock. Iwas hopeing someone could help me get it released.

thanks
johnny

johnny, September 2010

yes.manual lock on left h side near lift arm at back.to release pull lift lever back to constant pumping and pull
out manual lock and rotate until lock locks in out position.
hope this helps

james f, July 2011

Sorry to say but the hydraulic system on these tractors are very complicated compared to other makes i would suggest you leave it with a fairly heavy weight on the linkage overnight the arms will be partly down or all the way down then start up and only lift the arms up but not all the way then see if they will go down when moving the lever down if not you will need to get a manual and follow the instructions on this fault.

enginear, September 2010