Help! Curl cylinders acting up

[BayouMan]

OK folks, I have been meaning to present my problem here for several months, but I kept thinking , we got it fixed this time.

Bear with me as I give you the background info.

I have a 1978 JD-2640 tractor. I have owned this tractor for about 16 years now and I love the tractor! I've had my share of repairs to get it back in great shape. All of my repairs over the years, have been done by the same local shop. Got to be friends with the owner and told him I was thinking of adding a loader to my tractor. Several months went by and he gives me a call and says he has a used loader at his shop that will fit on my tractor. I decided to go ahead with the install. The loader is a Bush Hog brand and was on another John Deere tractor. That tractor had supposedly been vandalized. Someone poured Round-Up into the hydraulics and it turned his fluid into a jello like mix, almost like a grease.

Needless to say, this concoction was in the loader system as well. The left curl cylinder rod was bent by the previous owner and the shop was taking care of getting that fixed. I was helping with the install to save on labor costs, so I went to pick the cylinder up from the repair shop. They were just starting the repair and the tech came into the office with one of the 90 degree fittings from the cylinder. He showed his boss and me that there was this yellowish grease looking substance plugging the fitting. It came out easily.

Getting bored yet? Told you to bear with me.

Got the loader installed and was excited about my new toy! Then I started with the issues!

From day one, whenever I would get a full bucket of dirt, I noticed that the curl seemed weak. Even more frustrating, after I would raise the bucket up to dump height and begin to dump, the bucket would go about 2/3 of the dump cycle and then all of a sudden stop dumping. This is with me holding the lever in the dump position. (By the way, I have a 3 lever bank, bought new. the third lever is for a future grapple.) I then have to jiggle the lever back and forth and it will finally finish the dump cycle.

Took the tractor back to the shop. I just drove the tractor there since the shop is only about 4 miles up the road. Had my pallet forks on, running in 8th gear, and got to wondering where the tips of my forks were. Pulled back on the lever and to my astonishment, the tips came back into view! I had been into enjoying the scenery and not watching or expecting the forks to leak down. The tips had to be within inches of the pavement! I shudder to think what would have happened if those tips had caught the pavement!

The shop had the other curl cyl repaired. Still had leakdown issues. He then had a brain f**t and had a machine shop make him two new pistons. He had them cut an additional groove to accept another packing ring. Sounded good to me.

I just recently had the 2 lift cylinders redone, since they started leaking badly. Those still work fine.

I still, after nearly 1 1/2 years, still have the original 2 issues described above. Got the shop guy over the other day and had him witness me getting about 4 full buckets of dirt. Same issue of not completing the dump cycle.

Here is where I am beginning to question his hydraulic knowledge. He said that since this is an Ag tractor and not a commercial machine, that when I am dumping, the weight of the dirt is forcing hyd fluid out of the cylinders quicker than my system can catch up. I just sat there and said really!

This is where you guys come in. I have had the obvious things fixed or worked on. My hydraulic pump has been repaired. I think he even raised the pressure setting on my bypass valve. The stroker valve had to be replaced.

My thoughts about the leak down and weak curl function make me want to look at the valve. I'm thinking maybe some of the grease looking stuff has gotten up to the valve and is affecting the flow. I think some of this stuff may have damaged an o-ring or something and is the reason that I have the leak down issue. No visible leaks anywhere.

Sorry for the long story, but I wanted to give as much information as possible.

Any solutions, short of buying a new loader are welcome.

Thanks for your help.

Mike

 

[kennyd]

Sounds like you just need a new valve. Search the term "regen" for lots of reading on your problem.

 

[dcyrilc]

Looks like kennyd posted while I was reading. I think you have two seperate issues. As kennyd suggested, do some reading on regen. It addresses the issue that your shop friend was refering to when dumping. It is a real thing and not something he made up. I feel that the leak down/bleed off issue is a seperate problem... possibly a bad valve. Hope this helps.

 

[J_J]

I would remove the valve and take it to a hyd shop for testing before purchasing a new one.

 

[Egon]

Did all the Goop get cleaned out of all the lines?

 

[AKKAMAAN]

Everything is relative...I would like to see in what position that bucket stops curling....a photo or even better a video from the side position of the loader bucket, that shows the cylinders too.... there are some optional things that can cause your problem, one of them your shop guy already pointed out....

Questions!
Is the 3 spool control valve "new"?
Does the control valve give the bucket "force down" when dumping, or is it all by gravity??

 

[leonz]

RoundUp does a great job on chrome and most likely ate at the spools and spool o-rings and definetly destroyed your hoses.

 

[BayouMan]

OK guys, I have gotten a lot of information here. What should I try next?

The valves are new. The hoses on the loader are not new. I know that I witnessed him using a venturi set-up to blow the lines out with diesel and air.

Maybe I should try swapping the curl hoses over to the grapple valve to see if that solves the problem. I am willing to try anything at this point.

If the load in the bucket is causing the fluid to pass through the cylinder faster than my pump can make up the difference, wouldn't that indicate a bad valve?

I have talked to several buddies that have loaders on their tractors, and they all say that in the curl up function, that either you will bend your bucket or pick up the rear end of your tractor.

Any truth to these?

Should I move my curl hoses over to the grapple valve position and try it there?

Thanks again for your input.

Mike

 

[SSdoxie]

Since you have the 3rd spool not being used right now, try the bucket curl on it. If all works well you know it is in the valve, not cylinders or hoses.

 

[dcyrilc]

Here's some info on the regen function that's been talked about:
http://www.tractorbynet.com/forums/hydraulics/197912-regenerative-circuit.html

 

[kennyd]

The valves are new.

What valve do you have Mike?

If the load in the bucket is causing the fluid to pass through the cylinder faster than my pump can make up the difference, wouldn't that indicate a bad valve?

No, not at all.

Should I move my curl hoses over to the grapple valve position and try it there?

Sure, you have nothing to loose.

I have talked to several buddies that have loaders on their tractors, and they all say that in the curl up function, that either you will bend your bucket or pick up the rear end of your tractor.

Any truth to these?

Generally true. Do you know the specs for your machine (PSI and GPM)? Has the relief valve on the new valve beeen set to match the tractor?

 

[J_J]

A 3000 psi hyd gage would help solve most of your hyd problem. It will tell you if you have pressure and how much, and and allow adjusting of the relief valve. Install the gage at the IN port of the FEL valve.

 

[AKKAMAAN]

Maybe I should try swapping the curl hoses over to the grapple valve to see if that solves the problem.

Absolutely

If the load in the bucket is causing the fluid to pass through the cylinder faster than my pump can make up the difference, wouldn't that indicate a bad valve?

No, it just indicate the bucket is curling (dumping) faster than the pump can keep up with. If valve is new it can be assumed not being bad (as broke), but it can be "wrong spool" in the valve, spool for a single action function (power up, gravity down). If so, that function (spool) could meant to be for the FEL lift, or another aux function.....
Who provided the valve? A link to this valve available, or post valve make and all valve numbers....

I have talked to several buddies that have loaders on their tractors, and they all say that in the curl up function, that either you will bend your bucket or pick up the rear end of your tractor.

Any truth to these?

If pressure relief valve is properly set, it will relief before any damages happen. The bucket curl can not lift the rear end of tractor, but the FEL lift arms could, but that is not a preferred or common set up.

Should I move my curl hoses over to the grapple valve position and try it there?

Yes

 

[J_J]

Assuming flow at 10 GPM's, and 2 in bore, with 1 in shaft, the flow out the rod end will be around 30 GPM's

Pump flow plus regen flow would be around 40 GPM's. If this is true, you can see that a good load will generate more flow than the pump is pumping

Retraction flow, base end would be around 13.33 GPM's

What valve are you using, GPM capability, relief setting, etc.

As far as lift circuit leaking or curl circuit leaking, all valve spools have a drops per minutes leak rate. Some will stay up for months, and others you can watch them leak down. Depends on what you can live with. Shut off valves can help with some of that.

 

[Egon]

Seeing as everything was cleaned out maybe check out the cylinder bores as previously noted.

 

[wdchyd]

Seeing as everything was cleaned out maybe check out the cylinder bores as previously noted.

x 2


Seen this many times were the bores were scored but the cyl gets repacked anyways........especially the newer style cyls, the bores need to look almost perfect and smooth when they go back together.....some guys hone out the bore too rough thinking the bores will break in like an engine.....WRONG..!!

like others have said, pressure guages to rule out components will help by process of elimination.....:thumbsup:

 

[BayouMan]

OK guys,
There is a lot of information coming at me and I don't understand half of it. I went and looked at the 3 spool set-up on my tractor. I didn't see any identifying information. I'll have to call the shop guy and see if he has that information. It cost about $420 at the time.

I'll take some pictures of the spools later tomorrow. Got company (Grandson) coming by today. I'm not sure if it will be tricky or not to swap the hoses around. Looks like two different fittings were used.

If I can get BIL to help, I'll get him to video and see if I can capture the stall on dumping.

The leak down rate is not even close to acceptable. You can literally watch the curl leak down. Not good when you are trying to position something by yourself.

 

[dcyrilc]

OK guys,
There is a lot of information coming at me and I don't understand half of it.

If you need to. Take it in pieces and ask specific questions. That way we can give specific answers to help you to understand everything.

 

[TTTTTT]

I have a similar problem, but don't want to hijack the thread. May be resolving mine will help BayouMan. I have curl cylinders that also appear to have leak down. They will drop without any load on and quicker with a load. The main loader stays up with no problem. Including with engine off with no hydraulic pumping hydraulic flow. If I keep the revs up and constantly hold the curl up function on the joystick control I guess the increased flow will overcome the apparent leak down and hold the load (bucket curled) up. I switched the hoses to have the sideways joystick movement operates main loader and up/down on the joystick operates the curl function. Still have the exact problem of the curl leaking down. Returned the hoses to original setup with curl leak down.

The obvious answer is the curl cylinder seals are not holding and fluid is bypassing. The question is, do you assume both cylinders leaking, and if only one is, why wouldn't the other curl cylinder hold the curl up steady. Or do you just rebuild both and take the guessing out of the picture.

Am I missing anything or is it as obvious as it looks.

thx Dave

 

[wdchyd]

The obvious answer is the curl cylinder seals are not holding and fluid is bypassing. The question is, do you assume both cylinders leaking, and if only one is, why wouldn't the other curl cylinder hold the curl up steady. Or do you just rebuild both and take the guessing out of the picture.

Am I missing anything or is it as obvious as it looks.

thx Dave

It is as obvious as it looks......you did your homework, now proceed to the head of the class and repack those cyls.......

Only takes one bad cyl to make both in that same circuit to creepdown.....the best way is to do both cuz they both have the same amount of wear on them and you'll regret not doing them both.....that said some guys will figure out which one is bad first, then repack it make sure it is good, then proceed to number two to finish the job......DONE......:thumbsup: