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Crawlers, Dozers, Loaders & Backhoes Discussion Forum

JD 400 backhoe ??'s

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Larry

04-17-2004 18:38:16

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My backhoe is losing hydraulic pressure....like when you're using the backhoe and idle the engine down to talk to someone, I don't seem to have any hydrualics until I throttle up the engine to 1/3 to half throttle...I can hear the chatter of the oil building up, and then I've got pressure again. JDEmairs, I hope you'll help me here. I bought this backhoe a few months ago, so I don't have a whole lot of previous knowledge about it. The front end was loose on the motor and I drilled out broken bolts and blew one out with the torch and re-threaded it, put a new drive coupling on to the hydraulic pump, turned the system pressure down from 2600psi to 2000psi, and have fixed a few other minor things. I've been using it a little and I'm running into this no hydraulics problem. I've pulled the screen out of the bottom of the transmission and cleaned it (looked like it was about 1/2 coated with old teflon tape), changed the oil and the filters, JD, please advise me on that the most logical trouble shooting steps would be from here. Once you throttle it up, everything works, but I can hear the chatter as the pressure builds up. I destroked the pump while it was running and then screwed the destroke screw back in and I almost thought that everything seemed to be working normally, would the destroking valve cause a problem like this?? One more question Mr. Emaris...do you need to worry about getting this backhoe on too much of a slope and the oil pump not picking up oil? Thanks in advance for any help you can give me. I've always enjoyed reading what you've said to others, and if you can give me some trouble shooting tips, I's sure be appreciative. Thanks again.

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jdemaris

04-17-2004 19:26:49

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Re: JD 400 backhoe ??'s in reply to Larry, 04-17-2004 18:38:16

I think you spelled my name 10 new ways. Actually, (although I hate to admit it) my name is French and is actually "de Marrais" which translated into English means "of the swamp." As far as your hoe goes, if you keep on having problems you'll need to determine if you're losing your charge oil. The 8 piston hydraulic pump up front does not have the ability to draw oil to itself, i.e. it has to be fed oil - thus the reason for having the tranmsission "charge" pump. You don't need pressure in the oil, but there most be flow. Sometime when the machine is good and hot, you might try diconnecting the feed line that runs from the charge pump to the main pump. A Deere tech. manual would have a convoluted set of tests using a flow-rater - but it's not necessary. All you need is a bucket. Crank or start the tractor for a few seconds and see how much oil it delivers. As far as what you said about destroking the pump, then putting it back in stroke, and then it worked for a while - yes that happens sometimes, and often it's caused by a bad stroke control valve. I've had machines lose all their hydraulics, then destroked and put back into stroke, and then they'd work fine for while. I assume it was caused by a worn seat and possible debris that got stuck in it. A steep slope won't affect a machine that's working properly, but I've seen it cause a problem with machines that had internal problems - bad trans. pump, pickup pipe, etc. The way you describe the chatter before the hydrauics come back to life kind of sounds like it's starving for oil. I'd check the flow with a bucket before anything else. If you find out that at hot idle the trans. pump does not pump ANY oil, you're probably going to have to split the machine.

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Larry

04-17-2004 20:57:24

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Re: Re: JD 400 backhoe ??'s in reply to jdemaris, 04-17-2004 19:26:49

Thank you for answering me...I sure do appreciate it. My gut feeling was that the main pump was probably bad, What you said makes perfect sense to me...like when you start a 4020 and the 3 point arms chatter as the system pressure builds up. Let me ask you this....say I'm sitting at idle, should I have 2200 psi of hydraulic pressure? I was digging a trench thur a pond damn and my hoe was at a really steep nose dive angle...that was my question about the engine oil pump. I got the trench dug....turned out good (even with an inexperienced operator). I was just curious if a guy should be concerned with the the angle of the tractor What would you guess. Just based on your experience...is it the charge pump or the main pump?? I've got a 4020 and it will do the same thing when you start it, as the system pressure comes up. What will I run into with the transmission pump? Are parts available? I don't have any big concerns about gettting into it, what do I have to watch out for. Once again...thank you.

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jdemaris

04-18-2004 06:23:25

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Re: Re: Re: JD 400 backhoe ??'s in reply to Larry, 04-17-2004 20:57:24

The main pump is repairable; I wouldn't replace one anymore than I'd replace a complete engine. It has two large adjustable bearings, 8 replaceable intake valves, 8 replaceable discharge valves and seats, 8 pistons and springs, and the stuff in the valve body. If you run the flow test into a bucket for the transmission pump, and you are getting some oil, then you might think about pulling the front pump and going through it. Two gallons a minute at idle speed when hot should be fine. I've seen some that once hot, pump absolutely nothing. If the pump is working reasonably well, then you can assume the main pumping part of it is okay (the pistons and their bores). If the piston bores were badly scored, the pump would be a throw-away item. Chances are you could do a good job on the pump by installing a seal kit, eight new piston springs, and maybe new discharge disks if badly worn. If you find any worn pistons, you can replace them too. ABSOLUTELY replace the stroke-control valve. That wears before anything else, and will chatter, and make the pump work intermittently. The valve can be replaced without removing the pump. There is also a cylinder shaped cartridge filter inside the valve body that should be checked once in a while. It too can be accessed without removing the pump. If you decide the transmission pump is absolutely no good, seems it must be available. I haven't worked for a Deere dealer since 1989, so I've been out of the loop for a while. That system is used in many different machines and there are all kinds of things that can go wrong i.e. and e.g. pickup pipes and o-rings failing. Keep in mind that with the Deere closed-center hydraulic system, there can be all kinds of high-pressure leaks in the system after the pump, that can cause problems and rob your oil at slow speeds, including your steering valve, selective control valve (if you have one), etc. Check your manual to see how many posssibilites there are for leaks. Usual indicator of such leaks is hard cranking and starting. My neighbor has two 4020s and one 3020, all bought new. None of them will start anymore without destroking the pumps due to internal leaks. But, the leaks are small enough that he lives with them. If he didn't have the manual destrokers, he'd be burning out starter motors every week.

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Larry

04-18-2004 19:13:38

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Re: Re: Re: Re: JD 400 backhoe ??'s in reply to jdemaris, 04-18-2004 06:23:25

Thanks for answering. I had to work today, so I didn't have time to mess with my hoe. I'll have some time during the week and I'll get started on trouble shooting it. I can't even begin to tell you how helpful you've been....I really do appreciate it....I guess all I can say is....Thank you. I'll post back when I find out what going on. Thanks again

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jdemaris

04-19-2004 05:23:53

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Re: Re: Re: Re: Re: JD 400 backhoe ??'s in reply to Larry, 04-18-2004 19:13:38

One more general comment. I'm not real familiar with the "farm-tractored" based 300,400 and 500 Deere industrial tractors (although I have a 300). Most of the backhoe/loaders that I've torn apart and/or worked on were 310s, 410s, etc. which are designed from the ground up as dirt-moving machines. The 300s, 400s and 500s are basically farm tractors painted yellow. My 300 is, more-or-less a 1020 farm tractor with yellow paint, and I think the 400 is based on the 2020 farm tractor. 500 is from a 3020 ag. tractor. I mention that because the transmission pump hydraulic circuits differ a bit from the heavier 310s and 410s. Because the farm-tractor based machines are available with many options, e.g. reverser, hi-low aux. unit, live hydraulic PTO, etc., the transmission top cover and steel transmission pump circuit pipes can be a mess to figure out on some of the machines. Keep in mind that the aforementioned options all use the transmission pump oil for power. On the green farm tractors, we had a fair amount of problems with steel-pipe failures in the trans. pump circuits. That's why I suggested that you look at a hydraulic schematic or diagram of your particular tractor so you know where all the oil is supposed to be going, and where it's not.

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mark R

04-18-2004 15:35:10

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Re: Re: Re: Re: JD 400 backhoe ??'s in reply to jdemaris, 04-18-2004 06:23:25

Some more questions--
I have a JD300B back hoe loader that will not go forward down a hill--if you are facing up hill the shuttle shift works fine --on level ground sometimes it will go forward--and be able to move earth (power)--the hydrolics work fine on the loader and backhoe-- no noises that I can hear--
from the pump up front-- maybe some one has a quick fix or some good ideas -- thanks

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