New Holland Hay Baler trouble

[ratman916]

I have a New Holland 678 baler that I have been having troubles with. After dumping a roll the roller belts won't tighten back up. The arms won't release. Well we figured out if you let some of the pressure off the hydraulics then they would go down, however now we get loose rolls. I posted about this last year but never got the thing fixed. I can't seem to figure out how to determine which piston needs repaired. There are no hydraulic leaks anywhere on the baler. Each side has 2 pistions. I took #2 (see attached picture) off on each side and exteneded them out with the hydraulic lever on the tractor thinking maybe I could tell which one acted differently. Well neither would go back in once I extended them out. I was able to take a rachet come-a-long and decompress one side but the other side I couldn't budge. I had to raise the baler back end to get the one side connected back in the extended postion. I was wondering if anyone could tell me who in the central Tennessee area works on New Holland rollers or how I might determine which piston needs rebuilt.

 

[Tx Jim]

I looked at parts schematics and there's a hyd valve on LH side of baler that is attached to tailgate hyd circuit. Parts doesn't identify what valve is. Do you know it's function? It's possible it could be a relief valve that's malfunctioning.

 

[J_J]

If this cyl is a DA cyl, you can test if the cyl is leaking by removing the hose from the shaft end port, and extending the cyl.

When the cyl gets to the end of stroke, the fluid from the end port should stop. If fluid continues to exit the cyl port, then the piston seals are leaking.

Check each cyl the same way.

 

[RickB]

I'd sooner think you have a problem in the relief valve/check valve assembly than a cylinder problem. Does the gauge hold pressure when a full bale is tying or when the gate is held fully open? If so, think return check valve problems.

 

[Tx Jim]

Rick
What is the valve on the LH side that plumbed into the cylinder circuit? Is that the relief valve?

 

[RickB]

Rick
What is the valve on the LH side that plumbed into the cylinder circuit? Is that the relief valve?

Essentially the density control valve. A manually adjustable relief that restricts oil leaving the rod end as the bale forms. The hose at the top of fitting (#5) goes to a gauge that is visible to the operator and a test fitting where the system is purged & charged. The hoses leaving the valve at (3) go to the density cylinder on the opposite side of the baler. The system is a closed-loop deal with zero static pressure when the baler is empty and up to 1500-2000 psi at the rod end ports with a full bale. When the bale is dumped and the gate is closed, the large spring retracts the density cylinders and oil is allowed to free-flow from the base end to the rod end of the cylinders as the bale chamber shrinks to start position. The symptoms indicate the valve isn't allowing this free flow of oil to happen. I can't imagine anything going wrong with one cylinder that would (a) keep the cylinder from retracting when it extends normally, and (b) not twist the crap out of the pivoting belt carriage inside the bale chamber. And it is highly unlikely that BOTH cylinders suffered some type of failure that would create the symptoms. Gotta be in the valve

Edit: Cylinder #2 in the photo is the RH gate lift cylinder. I should state that the NH 6' balers with two density cylinders (678, 688, etc) have a somewhat different system than the 4x5 balers (644, 648, etc) that are nearly the only ones we sell and I have experience with. I know my operating theory is correct for the 678 model, and my details are accurate as well in that there is no connection between the density and gate lift circuits after a check of the 678 parts catalog.

 

[Tx Jim]

I thought I didn't see density cylinders on the same page as the lift cyl's & valve but it's been several hours since I viewed the page and don't know anything much about how the NH baler hyd's operate.Thanks,Jim