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JD 2950 cab tractor clutch issue

J

jdprobman

New User
Hey all, we have a JD 2950 cab tractor. Went to drive it and had half a clutch, won't disengage the engine. Seeing weeping around the master cylinder we suspected possible air-fluid exchange so we replaced the seals. While replacing the seals we drained all b-fluid from the reservoir and left it empty. We bled a lot of new fluid, the old stuff looked vile, through the bleed screw on the slave cylinder using a clean oil-can. We attach a clear hose full of brake fluid to the bleeder and then pump with the can once the bleed is open. Its supposed to force air up and out.
We tested the tractor and saw improvement, could actually drive it, but still had rough shifting on 1&2. Bled some more and got a couple more air bubbles out. Tested it again and now have a Very weak clutch. Can't do anything, just grinds if you try.
Just found out that this tractor has a HI-LO lockout, located under the cab, and so we've started bleeding from there instead because its past the slave and has a bleed screw.
Any tips on how to better bleed out infiltrated air?
NEXT DAY...
I tried something else I had read. We used a pry-bar to pry back on the slave cylinder's piston, then applied pressure from the clutch as we released pressure on the slave-cylinder piston. Once the clutch is to the floor and the slave rod is back, we release the clutch slowly.
This produced Alot of bubbles second time and a very weak clutch. A little more back-bleeding from the slave bleed made more bubbles and stiffened up the clutch. We've done this 6 times now with the same results, perhaps alittle less bubbles now. We've gotta eliminate the bubbles, so we'll keep doing this but we'll back-bleed from the bleed under the cab, the HI-LO lockout, instead. Any other ideas, anyone?
HOURS LATER...
From the amount of air that we were getting constantly from that method of slave-cylinder prying we decided that we must be leaking air into the slave cylinder when we release the clutch. I also heard something of a suction sound at the slave while the clutch is released. Is it possible that those are one-way seals for the piston in the slave that would allow air to force past? Is there any way that we can avoid creating that suction while releasing the clutch, like squirting fluid into a bleed screw while releasing the clutch?
I still don't think that the slave seals are shot because the slave was dry and clean when we started this game. The rubber boot on the piston was shot, but it was clean, too. Any ideas or alternative methods would be appreciated!
NEXT MORNING...
Got some papers from JD describing bleed process. Not any different than what we have been doing. People say that this is difficult, but should it take multiple hours?? With no real results? I am also beginning to wonder if this is an air issue anymore...
Thanks in advance
 

Everything I've ever read about bleeding the clutch cylinders on a JD Mannheim tractor implies it's very difficult to bleed and the hi-lo interlock makes it even worse.
 
First thing!!! REBUILD the slave cylinder. They can suck/leak air and not a drop of oil.

Then the only way I have every been able to get those tractors bleed easily is to pressure bleed them. The Hi-Lo interlock makes them just about impossible to bleed conventionally. The only way I ever got them to bleed just pumping the pedal is to hook your clear line to the bleeder. Put the other end into a can with enough brake fluid to cover the end. This will not allow the slave cylinder to suck air on the return stroke. Then fill the master cylinder up. Open the bleeder just to where it will allow a slow flow out of it. Slowly pump the pedal. Pausing with the pedal up all of the way. You may have to hook your toe under it at first to get it up all of the way. Leave the bleeder open and just make sure the hose in covered with fluid. I have had to pump several gallons through the system this way to get all the air out. IF you use a clean can on the bottom you can recycle that fluid. Once you stop seeing any air bubbles shut the bleeder and see if you have hard pedal. You should.
 
OK. I was told to bleed by pumping fluid from the end of the line back to the reservoir. D"ya think your way is better? Anything is better than what I"m doing now...which is nothing, waiting for inspiration, lol.
 
Just a thought... if the slave was shot would we get any stroke out of it? We seem to be getting a long-ish stroke, but haven"t been able to measure it. How long should the slave stroke be?
 
The trouble is that the slave cylinder is designed to only hold pressure one direction. The way you are trying to use it as a pump WILL NOT WORK!!!! It will suck in AIR 100% of the time.

Also who ever told you to bleed from the bottom is Wrong. You have to push the oil from the top down. The way the slave cylinder sets will allow an air pocket in it. You can't push it back up.

Also the way you are trying to bleed the slave cylinder retracted will work IF you do it correctly. Which you are not doing. With the slave cylinder pushed in all of the way you are making the volume smaller. This is easier to bleed. So here is how you would do it.

1) Hold the slave cylinder in all of the way.
2) Bleed it like you would normally. Meaning push the pedal and open the bleeder. Bleed like normal.
3) Where you are making a mistake. DO NOT let the slave cylinder out while the pedal is down. The pedal will force the slave cylinder out some when there is not air but do not let it move all the way out while the pedal is held down. Just make the fluid push you out some. Then let the pedal up. This opens a port to the reservoir. NOW let the slave cylinder out. It can suck the fluid down from the reservoir this way. The way you where doing it with the pedal held down makes the slave cylinder pull a vacuum on the system. There is no way for it to pull more fluid with the pedal held down. So it is more than likely pulling outside air in or air from the lock out cylinder.

Here is how I have always done them manually.

1) You can try to bleed the slave cylinder before rebuilding it. Just put your line on the bleeder. The other end has to be submerged in fluid. Have the bleeder open a little bit. Pump oil(with the pedal) through it until you are not getting any more air. LOCK the bleeder. !!!DO not push the pedal at this time!!! IF you do you will suck the air out of the lockout cylinder and have to start all over. Leave your line on the bleeder and the end submerged.

2) Put a second line on the bleeder on the lock out cylinder. Open the bleeder THEN start pumping fluid through it until you do not see any more air. LOCK the bleeder !!Again do not push the pedal any more now!!!

3) Move back to the slave cylinder. Open the bleeder and THEN push the pedal. You may see a little more air but it should not be much less.


4) Go back to the lock out and bleed it again.


You need to move fluid and air first. If you keep pumping the cylinders they work air back and forth between them and it will take longer to bleed them. So by using the hoses you can move the fluid and air in the cylinders without moving the cylinder pistons.

Work back and forth until you are not getting any more air. Then lock both bleeders and push the clutch down. You should have full pedal now. If you don't then the slave cylinder will have to be rebuilt. The kit is about $100 just for the piston.

You can get the air out this way it just takes time. LOTS of time. I have spent a day getting all of the air out manually.

Here is how I do it now. I have a pressure tank that holds about a gallon of brake fluid. It has a hose I hook where the reservoir usually goes on the master cylinder. The I apply about 5 psi air pressure to the tank. Then I go down to the slave cylinder and open the bleeder until I get ZERO air. The open the lock out cylinder bleeder until I get no air. Then I take my tank off up top. I then fill the reservoir while I have the line clamped. I hold my finger over the line and remove the clamp. I put the line back on the master cylinder while it has fluid pressure pushing any little bit of air out of it.

I can usually get the system bleed in under an hour this way. Email me if you want and we can exchange PH# and I can maybe talk you through doing it.
 
Wow, that's detailed! Thanks a bunch for all the info and the definite procedure. And thanks also for the offer of your e-mail and phone #, I might have to take you up on it. We'll see how the day goes.
I'm off to try it!
 
I have tried your method of bleeding, JD Seller, the conventional way with a clear line full of fluid from the slave bleeder submersed in fluid in a clean jar. The first two clutch down-strokes shot fluid, no air, into the line. After that we have gotten mostly air with a little bit of fluid. But, with every up-stroke of the clutch I can hear a sucking sound from the slave cylinder, around the rod. This makes me believe that the seals on the slave piston are shot and are leaking air with every stroke regardless. Would you agree with this diagnosis?
Thanks for your time,
 
Tried to test to see if the Hi-Lo interlock seals were shot, but there's so much air in the lines that it won't force any fluid or air out of the Hi-Lo bleed screw. The slave rod won't move when all bleeds are shut either.
Just wondering, how often do you see Hi-Lo seals getting shot? I also was told by someone that he often disconnects and caps off the Hi-Lo interlock. Claims it did nothing anyways, and makes it alot easier to bleed when its off. Ever done that?
 
I would agree with you. You are having so much trouble bleeding the thing I think you have had a master cylinder leaking for some time but still working. Then the slave cylinder failed. This is what lost you your pedal. So you fixed the master cylinder and not the slave cylinder. So now it is slave cylinder repair time. I would take it apart and see if you can match some automotive parts to it. The JD kit is outrageous in price.

As far as the Hi Lo lock out. I have not had many issue with them. They usually are fairly trouble free. You can plug it off and it would just be like a tractor with out that option.

I would just rebuild the slave cylinder and then try to bleed it like I out lined. Something to do to is to bench bleed the slave cylinder. Basically just fill it with fluid on the bench. You still will have to bleed it in the tractor but you will save a bunch of pumping this way.
 
OK, thanks for the info. The seals for the slave are on their way, so we'll replace them and should be good to go!
Are we going to have to adjust the slave at all to fit specs, or do we just assemble the same way we disassembled (eg. amount of turns on bolts, etc). Also wondering, what should the amount of travel be for the slave rod?

Thanks a whole bunch for your time!!
 
I usually just put them back like they come apart on a running clutch. There is an adjustment procedure but I only do that on a new clutch install. I have to look it up each time myself. Usually the clutch slave cylinder not working is a hydraulic issue not an adjustment one.

I think you should not have much trouble bleeding the system with a good slave cylinder in place.
 
What a run-around...
Jay Dee ordered the wrong kit. Parts guy can only order by looking at a picture, no description, and so he thought he got it right. Nobody in town has a seal that will match. So we took the piston off the slave to get the seal-groove machined deeper so that it will fit a regular hydraulic seal. After all this hopefully we can successfully bleed this thing.
 
1) You can try to bleed the slave cylinder before rebuilding it. Just put your line on the bleeder. The other end has to be submerged in fluid. Have the bleeder open a little bit. Pump oil(with the pedal) through it until you are not getting any more air. LOCK the bleeder. !!!DO not push the pedal at this time!!! IF you do you will suck the air out of the lockout cylinder and have to start all over. Leave your line on the bleeder and the end submerged.

2) Put a second line on the bleeder on the lock out cylinder. Open the bleeder THEN start pumping fluid through it until you do not see any more air. LOCK the bleeder !!Again do not push the pedal any more now!!!

3) Move back to the slave cylinder. Open the bleeder and THEN push the pedal. You may see a little more air but it should not be much less.


4) Go back to the lock out and bleed it again.


You need to move fluid and air first. If you keep pumping the cylinders they work air back and forth between them and it will take longer to bleed them. So by using the hoses you can move the fluid and air in the cylinders without moving the cylinder pistons.

Work back and forth until you are not getting any more air. Then lock both bleeders and push the clutch down. You should have full pedal now. If you don't then the slave cylinder will have to be rebuilt.
To quote JD Seller's advice to me before as a reference for the reason I did this.

I put the slave cylinder back together with the new, very stiff!, hydraulic seal in place of the old seal. It is now so stiff inside the cylinder that I cannot push the piston in with my thumbs, neither can the spring push it back at me. I can move it if I step on it. Is this too tight?
While I was at it I also took off the line to the Hi-Lo interlock and sealed off both the slave and the interlock. I filled the slave cylinder with brake fluid and attached my clear hose, full of brake fluid, to the bleed screw with the other end in a jar, submersed in fluid. The jar is slightly lower than the bleed, with a hump in between them that is higher than both ends. I ensured that the reservoir was full and opened the bleed a 1/3 turn. Instantly bubbles started to emerge from the bleed and caught in the hump.
I slowly depressed the clutch and got a horde of bubbles with virtually no fluid. The air forced all the fluid in my hose out the end, so when I went to slowly release the clutch I sucked a hose-full of air back into the slave! I tried again, but this time I filled the hose with fluid again [i:1552ac10ab]before[/i:1552ac10ab] I released the clutch. I sucked no air back this time, but when I checked the fluid level in the reservoir the level had not gone down. I have done this 5 times now and have seen no fluid drop.
The good news is that I cannot hear air being sucked past the slave seals anymore!
I also noticed, however, that if I leave the whole setup alone with the pedal up that it will slowly gravity-feed down and out the whole system. The fluid in the reservoir goes down, and I can see air bubbles [i:1552ac10ab]slowly[/i:1552ac10ab] coming up thru the fluid in the jar.

So, I am wondering a couple of things. I am thinking that pumping the pedal as I am is not working. So, perhaps I need to raise the jar above the slave, switch it out for a large funnel, switch out for a bigger hose, and fill the funnel with fluid. I wonder if that would help keep the air up away from the bleed and the hose full of fluid. This will not help the level in the reservoir go down, tho.
I am also wondering if I should somehow add to the reservoir to make it alot higher in an attempt to gravity-bleed the whole system from the top. I am afraid that this method will be too slow and leave air pockets in the bends and in the cylinders. I am no longer sure where all my air might be, so I am assuming that I have air [i:1552ac10ab]everywhere[/i:1552ac10ab].
I am also wondering if I can make a home-made version of your pressure-tank bleeding system. I'll look into it, but not sure if I can.

So, now that I have written a book I am awaiting advice! :idea:
Click to expand...
Click to expand...
 
We decided to modify the method of pumping from the top using the pedal. Instead of leaving the the bleed open and submersed in fluid, I have switched to shutting the bleed when releasing the clutch pedal. This has stopped it from sucking fluid back from my clear hose. I also have not heard it sucking air past the seal, nor seen evidence of that with the stuff that squirts out.
So, I'm putting pressure on the clutch pedal [i:da83da29e8]before[/i:da83da29e8] I open the bleed screw, opening the bleed, and forcefully depressing the pedal to the floor. I think being forceful gets the air out better than being slow. I then close the bleed and start slowly releasing the pedal. I then wait 10 seconds before redoing the process. The conventional way to bleed brakes.
I have a helper watching the level in the reservoir, and observing how much the level goes down per stroke. In the 2.5 hours I had to do it in we refilled that reservoir nearly 8 times. At first I was getting way more air than fluid, but now its tapered off to a short squirt of air at the end of every 2-4 strokes.
I don't believe that I have done this enough to get all the air out, but I am done for the day and wondering if there were any suggestions.
 
Success!! Here's what I ended up doing.
I changed the hose that leads from the reservoir to the master cylinder after finding 4 big cracks in it.
I just kept bleeding the system the conventional way you bleed brakes. The interesting thing was that I often had to play with how I released the clutch to get the fluid from the reservoir to flow down.
After a couple hours I was about to give up, as the flowing of the fluid was getting trickier to keep up and I still seemed to be able to occasionally squeeze little bits of air out, but I decided to try the clutch before I tried the other method.
It was stiffer than it has been since we started this game, and so I started it up. All the gears shift as smooth as hot butter, even better than when we got the thing! I took it for a little spin and had absolutely no trouble shifting to-and-from any gear.
It's fixed!! Thanks everyone for posting, and I appreciate all the advice that you guys have given me!! Especially JD Seller. Your tips were what did it!
 
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