Go Bottombackhoe fluid overflow
 | sarge1572
Join Date: Mar 2005 Posts: 9 so. california 
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2005-11-15 119399
I have a Jinma 284 with a FEL and a self contained (built in hydraulic fluid resevoir with its own pump that mounts on the tractor just above the PTO) JW-03 backhoe. I'm have a problem with hydraulic fluid blowing out the vent holes in the filler cap of the backhoe reservoir. I've filled it to the proper depth, checking it with the dipstick. I guess the first question is, is the fluid level in the built-in reservoir checked with all of the cylinders compressed? or extended?
I filled the tank with the backhoe cylinders compressed, and the outriggers extended to make the unit as level as I could. With the engine running at 1500 RPM I ran all of the cylinders all the way out, and in a couple of times, shut it down, checked the fluid level and it was right on the money. The backhoe operated smoothly.
While operating the backhoe under load digging, and I would curl the bucket, or pull in the arms, or even move the whole unit from side to side, I got a steady stream of hydraulic fluid running out of the vent hole in the filler cap. This was clear, not foam. Not when the arms were being extended, only when they were being pulled back in.
After this happened a couple of times I tried the following. The next time it happened I unscrewed the dipstick, creating a vent in the main tank. I heard air escape from the tank (not like a spray can, but slow like a large tank with some air trapped in it) and the fluid stopped squirting out of the filler cap vents.
I noticed that when I re-filled the reservoir (I drained it and cleaned it, only small amount of sediment on the bottom) with new fluid I could not fill the tank to the correct level unless the dipstick was out or the bolt it's welded to was pretty loose. If I left it screwed in tight the fluid would fill the tank up to the cutout in the bottom of the filler tube, then fill the filler tube. When I took the dipstick out the fluid level in the tube went down and I could feel, and hear, a small amount of air escaping through the dipstick hole.
(Don't beat me up over this next part) I had a small amount of digging to do cleaning out a corner where I'm building some corrals and left the dipstick loose in the hole so the pressure could equalize in the reservoir as I dug. No overflow. Not once.
1. Am I doing something wrong? (read dumb)
2. Can I (should I) vent the reservoir to eliminate this problem?
3. Do I keep buying hydraulic fluid?
4. Sell the backhoe and hire a couple of day laborers?
Thanks,
Jeff
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 | Chief
Join Date: Jul 2003 Posts: 4297 Southwest MiddleTennessee 
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2005-11-16 119407
Don't forget that once the hyd. fluid is up to full operating temp., the oil can expand up to 10%. There MUST be an unobstructed hyd. reservoir vent or you will have problems like you have described. There should be some type of tank vent on the reservoir either through the filler cap or dipstick or somewhere; if not you may have to make one. My 4410 has a small hole in the fill cap behind the seat. Everytime I lower the FEL bucket from full extention, I get a big wiff of hyd. oil which makes me instinctively stop what I am doing and check for a leak or broken hose. It is just the air being vented from the trans./hyd. reservoir. Sounds to me like you are on the right track. ....
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 | greg_g
Join Date: Jan 2004 Posts: 1816 Western Kentucky 
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2005-11-16 119415
The 284 has only a single 9 liter sump for all hydraulic requirements. That's basically enough to run the power steering, the TPH, and feed one aux. So Jinma included a separate sump with the BH. If you think about it though, no way you can allow them to both be full with cylinders extended. That leaves no room for the return fluid when cylinders are retracted. When topping up the sumps, it only makes sense that ALL cylinders be retracted. When extended they'll draw their required amount of fluid - then return it to the sump when retracted.
//greg// ....
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