I have a John Deere 310b with hydraulic pressure issues. I put a test gauge on both low pressure and high pressure ports. When I rev the engine to 3/4 throttle the pressure will jump to 2200psi but remains at zero on the low pressure side. If I lower the rpms to about half throttle pressure drops to zero. Any help would be greatly appreciated.
i am not an expert by any means,i happen to own a a 310a and have done a lot of work on it in the last few years. it looks like you have a supply problem.sometimes that can caused by a clogged screen or very dirty filter, or low fluid level,i would clean my screen first,if you need any help,let me know, i happen to live in bonaire,good luck.
Is this a closed center radial piston pump? Then you probably want to cap the output line and retest as the next step. DON'T do this unless you are sure you have a closed center radial piston pump system.
Hey neighbor...thanks. Yes I changed both filters and cleaned the screen but not at the same time. This is my first backhoe so I’m learning a lot about it. When I first purchased it about 3 years ago I changed the main horizontal filter then when I started having pressure problems I found the screen and the transmission filter. Both were completely clogged up with what looked like brake particles. Yes I’d like to get with you some time to share information. I’m about 2 miles south of 96 right across the tracks on West Houston. Thanks
Yes I will check I believe it’s a closed radical pump I will confirm this with my JD parts guy in Macon. He was a JD mechanic before becoming a parts guy. He knows a lot about the equipment. So testing with output line blocked would indicate main pump wear not internal gear pump if low side pressure is good correct?
Thanks for replying!
it is definitely a closed center system, i was always under the assumption that weak low side pressure was directly caused by something on the input side, but i could be wrong,i,m sure shane at flint equipment might could clear that up.i am 1 mile south of 96 on moody,let me know if i can be of any assistance.
I believe Shane told me you could have low input pressure at the test port on the side of the pump due to wear on the pump...I could have misunderstood him I will verify next week. Thanks
keep me informed. i am interested to know what you find out.
In normal operation, the pump output is blocked until a function valve is operated, this is what's called standby pressure that you're measuring. Blocking the output for testing purposes eliminates the downstream valves from the equation. So if there is leakage downstream that's more volume than the charge pump is supplying at low speed, then your pressure will change. The charge pressure is produced by a gear pump, but that pump rarely wears out (so I'm told), there are lots of other possibilities for the low charge pressure, it's leaking off in the transmission, or leaking off to the cooler, filter, or maybe somewhere else too. An "Operation and Test Manual" will have procedures for testing all of these components. The brake particles in the transmission are from the wet clutches and brakes in the powershift transmission, maybe not the end of the world on a 30+ year old machine that may have had the same filters for 20+ years.
Thanks for the explanation I am eager to learn as much as I can about how everything works. I may breakdown and buy a repair manual.
I sure will maybe one afternoon next week we can get together.
sounds good,by the way o got my repair manual on line, just downloaded the manual,was a pdf file,can,t remember where from,but i,m sure you can find it like i did.
Thanks I will search for it.
haven.t heard a progress report, still interested
Hey guys I’ve been out of town so I just got back to working on the Backhoe. I capped off the output line and checked the pressures. Didn’t change much still about the same. I’ve noticed it gets weaker once it gets up to operating temperature and will drop pressure to the point where the loader won’t lift. When this happens I can fully extend the boom and the pump will pressurize and raise the loader. Any thoughts I’m thinking either the internal pump is bad or something is restricting flow?
So with the output capped the charge pressure didn't register, and the output pressure jumped to 2,200 PSI only if you reved it to 3/4? And once it warms up and the hydraulics weaken, you can then extend the backhoe boom and make the loader operate? The loader valve may be getting cut off because the pressure is too low. If the steering and brakes are run off the same hydraulic system, then the priority valve cuts off the loader so you don't lose steering and brakes from too much oil going to the loader. The backhoe IS NOT cut off, so the backhoe might be allowing the hydraulic pump to stroke up and create enough pressure to turn the loader section back on. Or it's the low charge pressure that's causing the issue, because you're retracting the two biggest cylinders causing more oil to flow return than is going out the the cylinders when you extend the backhoe boom and stick and get the loader to work.
Low pressure side went up to about 40 psi and high pressure 2200psi. So you think it’s the internal pump? Is there a way to check internal pump pressure and flow?
No, go back to post #10.
Is that at idle or at full speed? Either way the improvement in charge pressure shows that there is some leakage on the high side. But that's still low charge pressure right? More than one thing going on most likely.
Procedure for checking low and high pressure systems is listed in the service manual . If I get a couple minutes, I'll pull my manual out and post the information for you. The manual calls out flow and pressure ranges at low and high idle speeds.
Also, Delmer is correct about there being a priority valve. It gives backhoe, brakes and power steering priority over loader function. Why? Because you aren't supposed to be operating backhoe while driving the machine, but you most likely are driving while operating the loader. In the event of a hydraulic pressure loss, the priority valve stops flow to the loader only so you can safely stop/steer the machine.
Low pressure did not move at idle got about 40 psi at 3/4 throttle.
Thanks.
just to add to what information you are getting from other members, i have also heard of the relief valve for the transmission filter,being stuck open by a piece of debris,might want to check that also.
Yes Sir thanks...I am out of pocket this week so maybe this weekend I can get back to it
ok let me know if you want me to come take a look
Yes Sir thanks
Here's part of the hydraulics information from my manual. The manual says it's for a 310A & 310B.
Here's some more. It's a bit of reading , but well worth it if you're turning wrenches yourself on your machine. I would upload the entire hydraulics section but I neither have the bandwidth or time to scan every page
Check out my post John Deere 310B Hydraulics Issue it may or may not help
Thank you Sir!
Thanks I will check it out!
How did you make out?
Hey guys I finally got a chance to get back to work on the backhoe. After thinking about everything you guys told me and Shane I decided to revisit the filters. Although I had changed them all but not at the same time I wanted to rule out restricted flow due to one or more of the filters being stopped up. So I started back tracking with the filter I found the most debris in so I pulled the vertical filter and it was clean then I pulled the horizontal filter and it was clean also. I remembered Shane or someone on this site saying it could be trash in the relief valve so I pulled the relief valve and found a piece of brake material holding the valve open. I cleaned the sleeve, reassembled installed filters and now everything functions as it should even at low idle. Thanks everyone for your help. Correction...I read back through the post and it was SBarrett that provided the information concerning checking the relief valve for trash. Thanks SBarrett
Yes and that is exactly what it was...a small piece of brake material. Thanks come by and see me sometime.
Easy fix. Good to hear
Yes Sir, thanks
glad you got it fixed,i came by one day a couple weeks back, but didnt see you outside,but i will stop by again,congratulations,
Thanks...if the white 2500 is there most likely I’m home