PTO Not Engaging / weak

[riderpriderking]

Hello friends!

I've been having a PTO problem for the last few months. It's too weak to use and sometimes won't engage or disengage properly. It's electric over hydraulic. I cleaned out the solenoid valve and the other valves in the PTO control block but it didn't help. I took it to a dealer, they said they tested the pressure in the block and it was randomly reading between 50 and 175 psi. They took it all apart and claimed to have found a little debris inside the solenoid. They cleaned it all, reassembled and it read 215 psi and worked properly. It worked properly a couple times but after 20 minutes of rototilling it was back to being weak. It'll turn the rototiller but if I stick it in the ground it'll stop. The only way to get it to work properly is if I dead head the rear remotes or use the 3pt hitch. Those operations just build up pressure in the line to 2200 psi or so which puts enough pressure in the block to open the clutch plates.

I've got the fluid drained and block off and it all looks pretty clean to me. I do have some questions though. I've attached a schematic of how the block is configured to help explain my questions.

Could someone explain to me what the Sequencing valve does? It's normally closed, at least when blowing into from the open end.

Also, in this scenario, what's the purpose of reducing valve? It's normally open if I blow into the end. Is it meant to close when I put excessive back pressure on the system to protect the clutch from 2200 psi?

What would happen if the reducing valve and sequencing valves were accidentally switched? Or plugged somehow? Basically could they be the problem here?

Lastly, where would the dealer have measured the pressure from? Would they have removed the bolt that goes to the clutch? Or would the G1 or G2 ports in the schematic have given those readings?

The hydraulic fluid and filter was replaced 50 hours ago and didn't seem too bad. At some point in the recent past there was an O ring that disintegrated in the loader valve. I was really hoping to find chunks of that in the solenoid but no dice. Any thoughts on what the issue could be or just to help me comprehend the operation would be much appreciated. Tractor is a Montana 4944 which is an LS 4020 which is similar to a NH Boomer.

View attachment TM Control Valve.pdf View attachment PTO Valve Block Schematic.pdf

 

[DirtHauler]

With not knowing anything about Montana tractors, I'm going to assume that the "PTO control block" is similar to what is on my tractor and others. With that said, the sequencing valve should be the one that when the PTO solenoid is engaged pressurized oil is allowed to flow this valve to the PTO clutch pack in a pressure graduated way (low psi to max) so that there is not a sudden and harsh engagement witch could potentially cause damage to the PTO and/or equipment.
In my experience what I've had to do to resolve some hydraulic issues, was to change out almost all "O" rings on valves, etc. due to fact that the cheap OEM ones "harden" and don't seal tight once everything gets hot and valve bores expand. This could also be the problem with your PTO. Worse case scenario, you may need to pull the PTO clutch pack and check the piston "O" ring(s). It/they may have hardened or split so when the oil and/or the piston drum get hot its expansion is allowing oil to escape thus loosing clutch pressure. As for the PTO clutch not releasing, I'd check for a sticking electric PTO solenoid valve and replace.

 

[riderpriderking]

Thanks, I found a manual that explains it all. I haven't fixed it but my research is also leading me to believe that it might be the o-rings. Thing is that when the dealer measured the correct pressure in the block then it worked properly, so my guess is that it's not in the clutch pack. So my question is then: Can I go get a standard pack of o rings from Harbour Freight/Princess Auto and find ones that are close? Or do I have to get a specific seal kit for that particular solenoid? What does everyone else do?

 

[oldnslo]

G2 in your schematic is the PTO engagement pressure and also the reduced pressure that should stay constant.

I can only guess but suspect the sequence valve is to keep a minimum pressure available for the PTO and this pressure would be seen on G1.

Can you install gauges in both G1 & G2 to see how they compare? If G1 is low this would indicate the sequence is malfunctioning which is also semi indicated by the fact that building pressure in the quick disconnect and the PTO works.

O-rings may or may not be standard sizes. They could be metric.

 

[riderpriderking]

G1 is how you test the sequence valve, which holds back pressure for the solenoid valve, I can test that and it is working properly. G2 is how you test the solenoid valve. It should match G1 when the solenoid is energized. Unfortunately it doesn't so that indicates that there is a problem with the solenoid valve. It's $300 to replace, but I'm wondering if fluid is getting by the o-rings and releasing pressure into the drain. I'm going to take the solenoid into a hydraulics place that will have a good variety of o-rings and see what they think. I'll let you know how it goes in a couple weeks.

 

[oldnslo]

G2 may not match G1 if the pressure reducing valve is working. I would expect the reducing valve to be in the 200 PSI range for operating the PTO clutch.

What do you see for pressure at G2 with the solenoid off? The pressure should stay very similar with the solenoid on. If the pressure decays or drops it could be the solenoid partially shifting or the reducing valve not working properly.

 

[riderpriderking]

Thanks for the help,

I've attached the relevant pages of the repair manual. I was able to test G1 and it is reading correctly at 227 psi. When I have the solenoid off G2 reads at about 100 and then slowly drops over time. I think that must be happening as the fluid is warming up. the longest I waited was until it got down to about 50 psi. When I turn on the PTO switch the gauge bounces between 50 and 140 to 170 depending on the test. The gauge fluctuates back and forth between 50 and 170 insanely fast. When I have it on G1 the gauge just sits at whatever the pressure is.

I tried replacing the o-rings on the control solenoid and it didn't seem to make a difference. According to the manual, and it makes sense to me, I'll probably have to replace the solenoid valve. It looks fine to me but maybe some tolerances are out or something like that.

I also tried to adjust the pressure reducing valve as mentioned in the manual and it didn't make a difference. I think it's set about 300 psi. When I dead head the rear remotes the pressure gauge in G2 usually settles out around 300psi although I don't really like doing that. I'm thinking I will have to replace the solenoid valve but I'm also leary of the reducing valve. The thing about the reducing valve is that it is normally open so i feel like it should be fine and I haven't messed with it since the dealer had worked on it so I think its ok.

Only other option I see is the PTO clutch if it was leaking hydraulic fluid somehow. I'd like to peer in on it but I don't like working outside on tractors in cold temps and the service manual doesn't indicate it's the problem.

Unless I hear something different soon, I'll bite the bullet and get the solenoid valve. Hopefully that solves the problem. Working on this tractor has been non-stop hydraulics trouble shooting for the last 8 months.

View attachment Repair Manual.pdf

 

[oldnslo]

Rider,
Per the schematic on page 3 in the service manual the reducing valve is valve 2 and the explanation calls that the sequence valve. Minor issue but something to note for future reference.
What I am unsure of is:
1) Where does the flow go through the solenoid valve while de-energized. Schematic shows it connected to the PTO clutch but suspect that it is going to tank. This is the only explanation for G2 being 0 PSI with solenoid de-energized.
1a) If the solenoid is partially shifting what would cause the gauge chatter? Possibly the time delay circuit is not getting enough flow causing it flutter or chatter.

have you verified that the 1.3 mm orifice is open between the reducing valve and solenoid valve? Is this a threaded plug or something pressed into the block or part of a valve?

Any way to bench test this block off the tractor? I doubt that it is the clutch pack and would certainly try to test the block fully before tearing into the PTO clutch. You would need a small power source pressure connection an some way to block the PTO clutch port. Be nice if you could put a gauge & needle valve in this port. That would quickly isolate the block from the PTO clutch pack and point you towards the failing component.
With gauges in G1, G2 & PTO port What do the gauges in all three ports do when solenoid is energized & needle valve in PTO port is closed? Are all three fluttering or just G2 & PTO?

If G2 & PTO check the tank port flow is it pulsing or spurting? If yes check the PTO delay valve.

If the gauges all stable with valve energized then open the needle valve slightly to allow a trickle of oil flow. Do the gauges go unstable? If yes this would point towards a leak in the PTO clutch pack allowing flow to escape causing the system to chatter.

Hope this explanation makes sense.

 

[riderpriderking]

Thanks oldnslow. I think I'm following your explanation. When the valve is de-energized flow goes through the control solenoid and into the tank. Then when energized the solenoid moves just enough to make it go into the clutch and not the tank.

The orifice does screw out but you have to take everything off to do that. It could be a little plugged but I don't think so. I definitely don't have the tools to bench test it but someone might.

On advice from a mechanic friend and the dealer I went ahead and replaced the solenoid valve since they thought it must be something in the PTO block. I'm still getting pressure readings around 110 psi instead of 220. Anyway, with the new solenoid the chatter in the pressure gauge gets pretty minimal. Now it just hovers around 110 and as the oil warmed up it actually got less. Once everything was warm I could turn the PTO on, it would spin for about 20 seconds then it would slowly slow down until it stopped. This is telling me that there is something leaking somewhere that is letting pressure bypass and then the clutch plates slowly disengage. Last time I checked I had proper pressure in G1 and the reducing valve is normally open, and adjusting it didn't change the pressure, and the solenoid is new so I just can't see it being in the block like the manual says.

I'm not sure what to do. I bought the tractor for about $15k CAD but since I've put about $5k in parts and dealer labour and 100's of my own hours. I need something reliable for our orchard and this is not doing it. I might see if the local LS dealer would do a trade in but I'm not sure if they would or not. Thing is I hate to lose money on the tractor but I hate to spend my life trying to fix it. I've fixed most of the other issues so I think If I got this one I'd probably be good to go for a while. Other than a new battery and maybe tires. The engine and the hydrostatic seem pretty strong.

Anyway, I appreciate any thoughts or comments, hydraulics or otherwise.

 

[riderpriderking]

Alright, I pulled off the cover over the PTO clutch and blew air in the solenoid control val at about 120 PSI. This video is the result. Montana R4944HST PTO Clutch Leak - YouTube. I'm assuming the clutch seals are gone. Can anyone confirm that it is not supposed to be leaking? I would assume not but I've been wrong before. When I talked to our dealer he said probably 2k to split it and replace the clutch. The clutch itself is about $600. I'd like to take a go at it but I just don't have the necessary space, time and tools to do it. On the other hand, I highly recommend The Tractor Company in Osler, SK. They are pretty good to work with.

Since I've replaced a lot of parts on this tractor, I'm thinking I'll keep it. It's pretty similar to a NH Boomer which seems highly esteemed. I think it must have been abused before I got it but now that I've fixed all those problems hopefully it'll be good for a while. I'll confirm that this was indeed the problem once I get it fixed.