2555 brakes revisited

[Harry in Ky]

So here I am, dazed and confused once again. I posted a while back concerning this tractor I had split for PTO clutch repair and put back together. Problems getting the brakes bled, but that has been resolved. Up to a point.

New situation and I find myself lost once again. Brake fluid supply is fine, the reservoir has plenty available and brakes bleed out as I feel they should.

Now I have a problem with the left brake where it will bleed out, have good pedal and brake action whether tractor is running or not, as long as it's sitting still. If I put in gear and start rolling, the left pedal goes all the way down and no brake action takes place. Stop the tractor, one pump and the pedal is back up. Hold the pedal down, put the tractor in gear and it will skid the left tire. Let off the pedal and as soon as it's rolling again push the pedal back down and have nothing again. This can be repeated a dozen times without change. Let it sit for five minutes and pedal is still there and solid. Roll the tractor as much as two feet and it's gone again. While rolling the pedal will come back after three or four pumps, but braking action is still weaker than I would expect it to be.

I was able to contact a retired Deere mechanic who knows these tractors far better than I, and he said right away it was a bad check valve in the brake valve. I can see some merit to that, but don't see how it applies to rolling or not rolling. I'm over my head here and I'm willing to accept any theory that has any logic, so I get a new check valve and freeze plug installed today and it made no difference. Same results. I've been trying to reach him for a few hours now and not having any luck there either.

I'm open to any suggestions.

 

[westga]

If I remember correctly you have a check
valve for each pedal. Make sure you
replace both sides. You have some
adjustments to make on the brake pedals to
do also.Its been along time since I did
this repair.

 

[Harry in Ky]

Yes there is a check valve for each pedal, but the only thing they have in common is they draw oil from the same reservoir. Not much else. Having replaced the one in question once already, i'm inclined to try capping off the supply line for the left brake next. Then operating the tractor as we have been, and see what that brings. If the check valve is the problem (or any part of it) the symptoms should continue. On the other hand, if the pedal stays solid without dropping off, the problem would have to be in the brake, brake piston area. "Old Guy" logic takes me to that conclusion.