D6M Breaking Issue

D6M 3WN00952 Breaks will not disengage, and transmission has low clutch engagement. Machine has no active fault codes and the transmission shifts through all the forward gears as well as reverse. It acts like the brake pedal is engaged keeping it at stall. I have checked the coils in both the park solenoid as well as the secondary brake solenoid both are getting proper voltage and the coils are in fact magnetizing. I can feel the solenoids actuate but have not verified visually. I’ve also checked the priority solenoid as well and it’s magnetizing and feel to be actuating. Pressure at the back of the tractor is 430+- and similar at the filter housing. All new filters and no debris present. Priority valve pressure is also in spec but the brake pressure is far lower than required. I’m stumped and mechanic is weeks out. Any suggestions?

I have also checked the bottom of brake switch and it is working but I don’t have a good way to test the pedal position potentiometer that’s connected to the pedal.

If by “transmission has low clutch engagement” you mean that the transmission clutch pressures are low when the parking brake is released that would appear to point to leaking brake piston seals.

Thank you, is there a procedure to determine which side it might be?

Before tearing into the machine wielding tools I would suggest a full pressure test of the power train might be in order at this point. See the attached. I would only take pressures and not attempt to make any adjustments at this point if anything is out of specification. Also can you give a bit more information regarding how this condition came about. Did it fail instantaneously or has it been getting worse for a while until it just quit.? Also how many total hours are on the machine.?

I purchased the machine inop. Everything else functions as it should. The machine has just over 10000 hours and has been well cared for. The story goes the machine was great used lightly as a ranch machine then it sat for several years and the next time they went to use it didn’t move after that. Pressure at the back of the machine at the relief port is 430, the test port at the filter housing is similar at 430, the pressure at the port nearest the priority valve solonoid is 140+- a couple lbs with the park break disengaged and 420ish when it’s on, at the break valve the pressure is similar with the brake engaged and falls to 120 psi after the break is released. The right brake only has 70ish lbs and the left is a little less than that both drop to zero when steering is applied. I have removed both the park brake and service brake solenoids and tested function visually.

WCLM said: the pressure at the port nearest the priority valve solenoid is 140+- a couple lbs with the park break disengaged and 420ish when it’s on, at the break valve the pressure is similar with the brake engaged and falls to 120 psi after the break is released. Click to expand... The fact that the pressure disappears when the parking brake is released is clear indication that the problem is in the brakes. At 10k hours it might be about time to reseal both steering clutch and brake assemblies. To be fair 10k hours on a ranch machine is pretty heavy usage. If you want some detailed information on removal and disassembly of the final drive & brake assembly just ask.

I was saying lightly used on the ranch being it was only run less than 100 hours in a span of 12 years. I’m not sure of the tractors past beyond that. I appreciate the insight. I feel a lot more confident deciding to dig into the brakes now. Thank you

You may find the attached information of some help.

I appreciate your time, I have a book now but having the part numbers is invaluable thank you!

I hate to beat a dead horse but after some more testing I have 115 psi at the priority valve with the park break engaged and 422 with it disengaged, the port on the filter housing is 418 parking break on and same 418 with it off, right clutch test port shows 195 with the parking break engaged and 195 with it disengaged and gradually drops to zero with the tip control activated, the right break port shows 14 with the park break on and 85 with it off and still 85 at full break pedal and tip control, left break is almost identical and the left clutch is similar to the right clutch pressure. I’m almost certain it’s a break piston I just want to rule out a spool valve or solenoid before I start disassembly. With everything being low but similar I worry I’ve overlooked something

WCLM said: after some more testing I have 115 psi at the priority valve with the park break engaged and 422 with it disengaged, Click to expand... Please refer to the Test & Adjust document I uploaded earlier. I attach it here again. In summary, with the transmission oil at normal operating temperature (around 170 DegF) and in neutral the Priority Valve pressures should be as follows. Low Idle RPM, Park Brake applied - 138 psi Maximum. Low Idle RPM, Park Brake Released - 424 ± 15 psi. High Idle RPM, Park Brake released - 138 psi Maximum. It may assist you to understand a bit better how the power train hydraulic system operates. See the attached SENR8387-01.

Something does not add right, U mentioned the machine does not release brakes, but u have the 30 something BAR as it should with brakes on? And it shifts through the gears? Thats what is not adding... U see, the system prioritizes pressure to brake system, brakes are activated by a spring, to release press is needed, if u have a leak enough to hold the brake, it wouldn't have enough press for shifting, cause pryority valve would not allow it. Nevertheless, resealing brake/steering clutches in a machine like that takes 2 hour in a 2 man crew. Then u can also inspect bearings and such in the finals... cost should not be over 300us with original seals. good luck

I do not have enough brake pressure to release the brakes. The pressure at the priority valve is within spec and the brake pressure at the test ports on the brake housing are 300ish psi lower than the required pressure to release the brakes. My original theory was a stuck spool in the priority valve but I have since ruled that out. My second theory was the secondary brake solenoid was stuck bleeding pressure from the system and now I’m thinking it could be a spool valve in the brake housing itself. The pressures I have listed are taken from the test ports and I have them in psi. The only thing with the required pressure so far is the priority valve port

Naa, u probably rulled out wrong... as far as i know the operating press control valve is mechanic... and sits downstream of the system... but your tractor has also some acumulators , to avoid bad gear selection when the system press goes dwn a bit... Nevertheless, if were u i would go after the charge pump... machine hours and Time Between last Pump was fitted tell u a lot about it... ppl say 4k hours, bit more on a OEM... Also the piston seals do last long ... a decade , decade and a half... U see changing the charge pump and reseal brakes and steer clutches if u have the finguer tip control, will be the cheap and easy way to get the thing sorted out. Ofcourse inspect the pump before throuing another in ...

Charge pump has 425-430psi and over 420 at the filter housing, the priority valve has a solenoid that actuates a spool valve. Pressure at the priority valve is within spec the problem doesn’t present its self until it gets to the brake valve. The priority valve never loses pressure, it has no codes and the brakes don’t have enough pressure to disengage. The system is losing pressure somewhere and I’ll have it sorted out soon enough.

Maybe the taps on top of final where it bolts to machine would help you narrow it down might use the steering to cut one brake out at a time

I’m gonna try and apply pressure to the brake ports to see which side is leaking pittsburgh cat man said: Maybe the taps on top of final where it bolts to machine would help you narrow it down might use the steering to cut one brake out at a Click to expand...

WCLM said: Charge pump has 425-430psi and over 420 at the filter housing, the priority valve has a solenoid that actuates a spool valve. Pressure at the priority valve is within spec the problem doesn’t present its self until it gets to the brake valve. The priority valve never loses pressure, it has no codes and the brakes don’t have enough pressure to disengage. The system is losing pressure somewhere and I’ll have it sorted out soon enough. Click to expand... IN that case, the problem might rest somewhere between the brake valve and the clutches. I´m more in the mechanichal version of those tractors, but i bet PRK BRK has one solenoid to activate deactivate , and service BRK has to have a spool divided in LH and RH wich is somehow conected to steering... Being your machine a Finguet tip control type, puling the lever fully activates clutch and the service brake of the side BRK. (in mechanichal systems that action is progressive) Try to figure out if u have Steering clutch press, positive when activated, and hook up a gauge at system press,(PV) Just to see if its related to the FTC... those modules are known to give some set of problems. good luck.

Your corrected priority and filter pressures indicate that the pump and priority valve are supplying the system correctly. The problem is that both brake-release circuits are only receiving about 85 psi. Since both sides are equally low, I would first suspect the common brake-control/parking-brake valve, a stuck modulation spool, or internal valve leakage—not two brake-piston failures at exactly the same time. Verify full pressure into the brake valve and measure its outlet. Then isolate each brake line individually. Only if a brake circuit will not build or hold approximately 424 psi when supplied separately would I pull that steering-clutch/brake assembly for piston seals. That isolation test should prevent a very expensive unnecessary teardown.