I have a john deer 300 backhoe that is blowing the seal and even broken the bolt off that holds the canister cover over the hydraulic filter. Is this being caused by a clog in the hydraulic lines or a check valve stuck. If so where are they located? I was told it could be a relief valve problem at the hydraulic pump at the front of the backhoe . I really don't know where to start to solve the issue . Any experienced advice would be greatly appreciated. thank you
I'm mostly guessing because I'm not familiar with the 300, that's getting a little long in the tooth. Look on jdparts.com, the parts catalog shows great expanded views of all the parts. There are several o rings in the relief valve that is part of the filter base. Any of those o rings could cause problems, or a broken/bent spring, or some junk, or a scratched spool, etc. That's the first place I'd look. The pump has a stroke control valve, I don't think there is a relief valve near the pump, except maybe a cooler relief valve in the oil cooler circuit. Who told you it could be the relief valve on the pump? I couldn't tell you how the stroke control might or might not cause the filter to pop? Have you let the fluid level drop, or had air in the hydraulics? Have you checked the suction screen (in the transmission?)?
300 backhoe we did have 4 lines replaced and both axles off backhoe .The unit had been setting for about 18 months with all the fluid out off the unit. I have not checked the screen in the transmission . Is the relief valve next to the filter base or inside the unit? It was just a neighbor who said there was a relief valve in the pump I don't know where he got that info from. Could there be enough air in the unit to make it build that much pressure? THANKS FOR THE REPLY
It looked like the relief valves were inside the filter base, just look it up and you'll see what you should get out when you pull it apart. I wasn't sure about the front pump causing this so I wanted to know if this was some wise old Deere guru who told you that. Who knows? I'd start with the filter relief valves, and suction screen, and working the air out of the system slowly when you have to "open it up". In general, Deere or most other equipment, the hydraulics are a "semi-closed" system, the fluid circulates through the pump, through the valves to the cylinders and back through the filter to the pump. The relief valve is designed to open when a big cylinder retracts (more fluid coming back than out) and that fluid is pumped back by the charge pump when that big cylinder extends. If you happen to have air in one end of a cylinder that's at full pressure, the stored energy in air pressure can rupture a filter or worse. The relief valve just can't dump enough fluid to keep the pressure from spiking from the surge of fluid.
I HAVE ANOTHER QUESTION TO ASK , where is the best place to bleed the hydraulic system to get the air out? I purchased a new bolt and filter for canister and I have located the relief valves but am uncertain about how to know if their stuck or working proper how do you know or test them? I don't wont to sound dumb but I am afraid I will blow the canister off again or do damage to the hydraulic system .Any more advice would be greatly appreciated. THANKS HILL L
From the operators seat, just start it up and run it slowly through the functions, at idle and with the levers/valves fully open, don't let it build pressure, use two or more functions at the same time so that as one cylinder hits the end the fluid goes to another cylinder while you move the first control to the opposite position. You can either use the technical manual from Ma Deere, and pressure gauges. Or you can pull the relief valve out and inspect the bits.
Hello did you find out the problem? Becouse my machine is doing the same thing!
The Deeres of this era did have a somewhat closed system, half the front pump inlet flow comes from the transmission pump, the balance is provided by it's own return oil from the loader and backhoe flowing through that filter. The pressure contol valve which dumps excess oil back to the tranny is in the return filter head, usually a hex plug on the side away from the transmission case comes out, there will be an extended rod as part of the plug. The rod is the stop for the relief poppet, which has a spring behind it. If the system has has some debris in it it is not unusual for this valve to stick open which starves the hydraulic pump, or closed which usually blows the small hoses clamped to the lines in and out of the filter head. there is also a smaller bypass check valve in the head, but that just bypasses the filter element when it clogs up, it won't affect the system pressure.
I have a john deere 1982 310a backhoe it has 2 problems 1/ it has slow hyd's 2/ it blows out hyd oil from the filter I checked the filter relief valve and the screen in the bottom of the trany looks ok! help
Which filter? And did you check both valves if it's the left side hydraulic filter? Also there's a short piece of hose connecting the filter head to the transmission case where the suction strainer is I believe, check for blockage.