John Deere 2940 Left Right Brake Problem

[purplehiss]

I can't seem to get the left and right brakes working on my 2940. If I brake with both pedals, I get solid braking. Applying just left or right, the brake depresses all the way with no power. I can trick it by applying both and sliding my foot left or right on just one pedal, but that is harder to control.

I know this is typically an equalizer problem in the control valve, but I have pulled them both and find no issue with the springs or balls. The o-ring is just a seal on the outside cap. I guess the internal valve seat could be an issue, and I have tried to clean it, but I can't see how it would leak as badly as it seems to.

Any suggestions on further checks? I'd like to get the brake steering going before the snow gets deep.

Thanks.

 

[beenthere]

Have no direct knowledge of this brake valve, only can post the schematic of the part shown in jdparts.com.
If it looks like this, may give you some idea seeing the different parts.

 

[Tx Jim]

purplehiss
I think although you have addressed the equalizer valve the brake problem still lies with a faulty equalizer valve.

 

[Zebrafive]

I agree, equalizer is at fault. Is the ball seat OK? Is the seat replaceable? If not, maybe you can get dremel tool with a round ended bit that you could use to polish the seat with valve grind compound? Or maybe you will have to replace the housing to repair the ball seat?

 

[purplehiss]

I agree, equalizer is at fault. Is the ball seat OK? Is the seat replaceable? If not, maybe you can get dremel tool with a round ended bit that you could use to polish the seat with valve grind compound? Or maybe you will have to replace the housing to repair the ball seat?

Thanks Zebrafive. The ball seat is part of the casting as no separate seat is in the diagram (thanks 'Beenthere'). The valve casting is prohibitively expensive, so your dremel idea is certainly worth a try.

Thanks again to all responders!

Steve

 

[jd110]

Your problem may be in the stop crew adjustment for the pedals. Try adjusting the screws by loosening the jam nuts and screwing both screws in far enough that they are not contacting the pedals. Then back them out until they touch the pedal and then back them out an additional two flats of the bolt(one third turn). After that if one pedal is higher than the other, back that screw out one flat more to even them out. I have had many of them be cured with this adjustment.

 

[purplehiss]

Thanks jd110 for your idea. Unfortunately, the 2940 does not have adjustments on the pedal stops.

I like where you were taking it though. Seems to me if one of the pedals was just slightly 'on' and porting a small amount of fluid continuously, hitting the opposite pedal would drive fluid through the equalizer.

It's very puzzling to me. There are two equalizer valves. They are very simple steel ball valves. Not enough action there to ruin the seat. Seems very unlikely in any case that they would both go at the same time. My history with the tractor is limited, but the owner says they both quit a couple of years ago.

Anyway, thatnks all for the ideas, and if anyone else has a thought, please share it!

 

[jd110]

If you have no stop screws, then they are missing. Should be 2- 3/8" x 1 1/2" bolts and jam nuts. There should be threaded holes in the valve body. I am attaching a picture of the screws on a cab tractor valve, open station is similar. bolt and nut is #10 and 11.

 

[purplehiss]

If you have no stop screws, then they are missing. Should be 2- 3/8" x 1 1/2" bolts and jam nuts. There should be threaded holes in the valve body. I am attaching a picture of the screws on a cab tractor valve, open station is similar. bolt and nut is #10 and 11.View attachment 404862

jd110 - you are the best. Thanks for knockin' me upside the head! :drink:

I went back and looked at the right area as you described, and the pedal stop screws were there of course. Ten minutes to get them set right per your instructions and I now have left and right brakes! It must be that brake pistons allow bypass if there is any freeplay in the pedal. I only had 3 or 4 mil, but that was enough to cause the equalizer valves to send the hydraulic fluid down the low pressure path. One full turn of the stop screws and the differential braking is 100%.

Thanks again!

 

[Tx Jim]

jd110
Did the 2940 brake valve get system hyd pressure instead of trans pressure to fill brake valve reservoir? I was looking at the hyd line routing for 2940 and it appears brake valve gets it's pressure from steering valve unlike the smaller utility tractor models that the brake valve gets it's oil from trans pump via hole in trans case. I sure wish I had known about adjusting the brake pedal screws to correct braking problems way back when I was a JD service manager.
Thanks,Jim