1256 brake problem

I have been chasing this problem for a while. If I push on both brake pedals at the same time they go all the way down with virtually no braking at all. If I pump the brakes once and hold them down the pedals will eventually push back at me and I will have brakes again. If I let off the brakes and push them back down, no brakes again. Now here is where it gets really wild. If I push down only on the right brake, it works fine. If I hold the right brake down (working correctly) and then push the left brake down with my left foot, both brake pedals will go all the way down and no brakes. Left brake will not work at all unless I pump it like I described above. Anyone had anything like this happen before. I have been through the whole system once, but must have missed something. Help please.

Take the top off the brake valve the bolt on that left brake valve has back off its on the of the valve

Thanks for the information. I just went out and check the screw on the back of the brake booster rod and it was tight. The spring appears to be held down about the same as the other side and the upper part is tight. The oring on the piston also seems to be fine. Any other thoughts?

Yes we are chasing the same problem on a 574 IH. Their is a equalization valve between the 2 master cylinders. If one brake is working and one not they both go down when you press both at the same time but will work independently. We ordered a new master cylinder but it has not arrived. Upon further investigation we found that their is a screen in each line and a orifice to limit the flow of oil according to the IT manual to each brake. Trouble is the IT manual doesn't say exactly where in the system they are located!! We think it may be before the master cylinder and stopping the flow of oil to it.. or maybe one before and the other after or it may be the master is bad. That's why I hate IT manuals, much prefer the original IH.. Sorry this got so long winded, it's only 24 degrees/ snow so it will be a couple of days before we get it shorted out. Hope some of this helps, will post when we get it solved.

Im going to demonstrate my ignorance here.

If these are hydraulic brakes with a common fluid reservoir then is it possible there's a crack somewhere that's allowing fluid to pass from one master cylinder to the other....or a machined internal passage that's supposed to be plugged. That one pedal disrupts the other pedal hints there's some kind of unexpected fluid communication between the two sides or there's a check valve that's being upset off its seat.

If these are complete mechanical brakes then the above is wildly incorrrect!

Have took that brake apart

Have you try to Bleed the brakes they are not a pressure fed
system when you bleed the brakes you push the pedal down
and bleed the pic cock and let up then push down bleed keep
doing this until you get no air it take time and Usually it is the
brake pistons that seeped the oil past the O-rings On the
brake piston in the rear end housing

Seem's I jumped and answered before looking, the 1256 brake system is completely different than the 574, so my comments are irrelevant to your question..

First of all you don't have to pump the pedal to gain any braking. Just push the pedal down and then the flow will start to come into valve and on to the brake. It is normal and in fact the way I check to see if brakes are working properly to depress one pedal a tiny bit and then the opposite pedal should go down to the floor. Part of the self equalizing in the spools.

On your tractor the first thing I would do is check the adjustment of the pedal linkage. If one or the other or both are adjusted too tight you can have the problem you are experiencing . You want all pins to be free, turn easily and have to move pedal just a tiny bit to tighten the pin. Often times they are rusted and or adjusted too tight.

Then, check each brake separately. Hold pedal down and you should have brakes almost immediately. If one or both go down and build pressure in a few seconds and then you have brakes you have one of two problems. Air in brake most likely and bleed them with a hose on bleeder. You can run the hose right back into the oil filler hole. Hold pedal down while bleeding until clear oil comes.

Other problem if not air would be the self adjusters and brakes them selves. If adjusters back off or are uneven, the discs have to move too far to get brakes. If the screw under the cover backs out the usual problem is a dragging brake because pedal cannot come all the way off pressure. Also, has this brake valve been taken apart and the two spools mixed up . They are different even though you will have to look close to see the difference.

You are right I don't have to pump the brakes, but for what ever reason, that helps the left brake pick up pressure sooner. I have bled the brakes before. I suspected the adjusters and checked them, but I must have missed something something on the adjusters.

I did have had the brake valve apart and the spools out. I don't think I mixed the up.

Thank you all for the information. I will give you an update tomorrow.