Mysterious yearly hydraulic leak

[victor43]

Have a 1996 B2400 HSD Kubota with a front mounted snowblower. Last year when I installed the snowblower and raised it about the third time, noticed that there was hydraulic fluid dripping off the radiator grill. Also some hydraulic fluid under the cylinder. Couldn't fond the source of the leak. Used it last winter without the leak showing up again. Just finished installing the snow blower and had this one time leak again. Couldn't find out where it was coming from. Did a test---put paper towels around the top of the cylinder, the hose connection to the cylinder and the air bleed (?) on the top of the cylinder away from the hose connection. Raised and lowered the blower three to four times. Everything dry except trace fluid on the air bleed. Attached a thumbnail. What is the threaded thing attached to the cylinder opposite the hose connection (that i'm calling an air bleed)? If this is an air bleed, could it be sticking and releasing fluid? Does it require any adjustments? Hope someone can help solve this problem. Thanks

 

[flyerdan]

It appears that you have a double acting cylinder being used in a single action application, which is fine; the port without a hose has to be vented to atmosphere to allow it to cycle without trapped air creating pressure / vacuum problems. If it is leaking from there, it would be fluid that is going past the seals on the piston.
What I'd be more concerned with is how you have it plumbed into the front remotes, I'd think that there are two lines for a double acting system, and if one isn't used in the application it will be dead heading somewhere, and that isn't good.

 

[JWR]

Nah... using a double acting capable cylinder in single action mode does not require any sort of air vent. The unused port is typically just hard plugged, as your's probably is. Can't tell from your description but my first guess is that your steering cylinder is leaking at times. That is a frequent occurrence with small Kubotas. I have had it on my BX2200 and know of another that got bad enough they rebuilt the cylinder. The dealer who rebuilt the cylinder said it is fairly common. The steering cylinder is far forward at least on the BX models and I assume on your's too. In my case the leak developed in very cold weather with my impatient jerking of the steering wheel before things had a chance to warm up. It leaks slightly off and on and I bought the cylinder rebuild kit but the leak stopped. So far I have not had to install the kit. Been going on now for 2 years.

 

[victor43]

I just noticed that if you enlarge the photo, there is a small hole on the nut of the air bleed that points to the front of the tractor. When the leak occurs, thr sprayed fluid is only on the outside of the grill. There is no fluid on the radiator side. When a double acting cylinder is being used in a single acting mode doesent there have to be someway for the air to get in and out (an air vent)?

 

[JWR]

I just noticed that if you enlarge the photo, there is a small hole on the nut of the air bleed that points to the front of the tractor. When the leak occurs, thr sprayed fluid is only on the outside of the grill. There is no fluid on the radiator side. When a double acting cylinder is being used in a single acting mode doesent there have to be someway for the air to get in and out (an air vent)?

No. Air is very compressible and hydraulic fluid is not. The small amount of air trapped in the unused end of a cylinder is negligible in terms of pressure or behavior of the cylinder.

 

[boomer1025]

The reason your getting fluid/oil out the air bleed valve when first using the cylinder is because as it sets over a period of time the oil on the fluid side of the cylinder leaks past the piston seals and into the air side of the cylinder. When you hook it up in the fall put a rag over the air bleed and that should keep the oil off the grille.

 

[flyerdan]

If nothing else, you need a vent on the end of the cylinder to purge any fluid that seeps past the piston seals, or otherwise it will accumulate to the point that you no longer have full travel; if it leaks enough it won't move at all because the volume will be equal on both sides.