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Back again JD 410 backhoe hydro problem


 
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chrisb
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PostPosted: Fri May 25, 2007 4:35 am    Post subject: Back again JD 410 backhoe hydro problem Reply to specific post Reply with quote

Hi all,

Last fall I replaced the broken ring and pinion on a 1979 JD 410 backhoe. After I got her up and running I blew a line to the loader bucket, replaced the line and then lost hydro pressure. It should be worth mentioning that the system was "open" for months and it I feel that it got dirty.

I had posted in here last fall and some good people where kind enough to help.

I guess the best way is to list out what I have done so far.

1. Tested the pump pressure with the rear hydraulics plugged off at the power-steering T and the pump read about 2400psi. As well I have 130psi at the reverser control.

2. Replaced both filters (tranny and hydro).

3. Cleaned the transmission screen.

4. Cleaned the transmission relief valve.

4. And just yesterday completely disassembled and cleaned the speed gear assembly (reverser) control.

Still nothing. Pump still reads only 500psi.

One thing I did notice yesterday is the hydraulic pump to pressure control valve seems hot while running. Other lines seem about the same as outside temp. I know someone had mentioned that a hot line points to the leak / problem, but where? Does that mean the pressure control valve is leaking?

Some of the things I am thinking of looking at today.

1. Bypassing the steering. Someone here suggested it.

2. Try to understand the loader control valve and clean or bypass it. My thinking is that if the loader line blew would not a influx of oil pass through the loader control valve, possibly picking up dirt and thus creating a leak?

3. Revisit the pressure control valve, due to the pressure control valve to pump line being hot.

Other then that I am at a loss here. Any help or other ideas would be greatly appreciated.

Thanks in advance.
Chris

 

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chrisb
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PostPosted: Fri May 25, 2007 4:39 am    Post subject: Re: Back again JD 410 backhoe hydro problem Reply to specific post Reply with quote

After taking a look at the loader control valve in the manual I wanted to add this much as it might be helpful for the experts here. The hose that blew was on the bucket of the loader. Currently most of the hydraulics barely move, but the loader bucket moves a lot faster and is pretty much the only one that can make a full cycle (as in it can completely move to the limits in both directions).

Thought this would help..... maybe not?

Thanks again.

 

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jdemaris
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PostPosted: Fri May 25, 2007 4:51 am    Post subject: Re: Back again JD 410 backhoe hydro problem Reply to specific post Reply with quote

I don't understand much of what you are describing. The hydraulic "pressure control" is built into the hydraulic pump. The tractor itself has a hydraulic priority-valve and is supposed to send all available pressure oil to the steerring - before anything else gets it.
The front hydraulic pump cannot draw oil to itself - it must be fed oil. No pressure needed, but it must be kept supplied with oil. If it is NOT getting oil, it will do nothing.
You have to find out - first - if your main hydraulic pump getting oil - or is it not?
If it IS getting oil, and won't make pressure - it is a pump problem.

 
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chrisb
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PostPosted: Fri May 25, 2007 5:01 am    Post subject: Re: Back again JD 410 backhoe hydro problem Reply to specific post Reply with quote

jdemaris,

Sorry for the confusion. By pressure control valve I mean the pressure control valve at the back off the transmission, the one that diverts fluid from the hydro pump, which I might add I have cleaned out.

If I assume correctly plugging the lines at the power steering T and seeing 2400psi on the gauge at the pump means that the pump is getting oil and the pump is fine. With the line not plugged (tractor as normal), I am getting only 500psi.

So is it safe to assume that the pump is getting fluid and the pump is fine? Pump only has about 250 hours on it as I replaced that about 4 years ago.

 

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BobH from Missouri
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PostPosted: Fri May 25, 2007 6:15 am    Post subject: Re: Back again JD 410 backhoe hydro problem Reply to specific post Reply with quote

Chris
This happened 30 years ago on my 1972 JD310. Kids poured sand in the system while the backhoe was sitting on a construction site. Long horror story about the months of work to get the tractor right again. All hydraulics were slow, multiple tests to try to figure it out, and one day the JD service man rapped on the valve set down by the brake pedals with a shop hammer. Everything started working. We figured a relief or bypass valve was stuck. By the way, the hydraulic fluid would turn milky and get hot from being saturated with air after running the tractor a while. Sorry I can"t remember the specifics, but I do remember it cost me dearly in service calls.

 
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jdemaris
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PostPosted: Fri May 25, 2007 8:48 am    Post subject: Re: Back again JD 410 backhoe hydro problem Reply to specific post Reply with quote

When you cap lines, you might be eliminating any flow-demand on the main pump. So, it is not necessarily showing you the pump is good - or not good. For example, a pump being tested for PSI when it is only pumping 1/2 gallon per minute - might test completely different when PSI tested when pumping 25 gallons per minute. That's why flow-raters are often used for diagnostic work.
Generally speaking - if the feed line going TO the main pump - FROM the transmission pump - can fill a 5 gallon bucket in less than a minute -then you've probably got enough oil feeding the main pump.
You might just have a high pressure leak that is demanding more oil from the main pump - that it can give. Usually, leaks on the high-pressure side gets hot real fast and are pretty easy to find. They also tend to cause very hard cranking and starting unless there is a pump-destroker installed.
Also keep in mind that transmission pump often get ruined when any metal parts fail in the trans. or rear - because metal runs through them. Transmission pump is what feeds most of the oil to the main pump. Again, do the 5 gallon bucket test.

 
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chrisb
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PostPosted: Fri May 25, 2007 12:49 pm    Post subject: Re: Back again JD 410 backhoe hydro problem Reply to specific post Reply with quote

JDE,

Thanks again for the help. I just got back from the 5 gal bucket test. I think bad news as it was only about 3 gals in a minute if that. I used the clutch control valve to pump inlet line.

So where should I attempt to look next. Or is it a definite that the trans pump is shot?

Funny thing is that I have no diagrams or manual on the internals of the trany. I am using the CD-ROM manual which is nothing more then a Military manual. Seems to cover everything but the internal of the tranny.

I assume getting to the tranny pump is tedious and costly? I have spent more time trying to find the problem here and would hate to go all the way with the tranny pump replacement only to find it not the problem. Going off the deep end here. Smile

One last thing. The brakes are empty and I have not bleed them yet, but now I see in the manual that the brakes are fed from the tranny? I will have to look again, but I thought they were a completely independant manual system with no feed from the tranny.

Thanks again for any more help that anyone has to offer.


 

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Case450
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PostPosted: Fri May 25, 2007 5:09 pm    Post subject: Re: Back again JD 410 backhoe hydro problem Reply to specific post Reply with quote

maybe the hydraulic valve blocks are shot?????? You got a bit of a head scratcher there my friend...lol...good luck!

 
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jdemaris
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PostPosted: Sun May 27, 2007 2:58 pm    Post subject: Re: Back again JD 410 backhoe hydro problem Reply to specific post Reply with quote

Seems 3 gallons a minute is not bad enough to cause your problems unless you are testing only at full engine speed with the system cold. What is it rated, around 7 GPM? That's not a rhetorical question, I just don't remember off hand. I had to fix many that - once hot - pumped zero at engine idle-speed when warmed up. That DOES cause problems.
Remember, that the main hydraulic pump is also getting oil back from the return circuit whenever you are using hydraulics - the trans. pump just has to make up for the difference.

 
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john_bud
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PostPosted: Sun May 27, 2007 7:45 pm    Post subject: Re: Back again JD 410 backhoe hydro problem Reply to specific post Reply with quote

Is there a pressure relief valve near where the hot part is located? If so, it may be stuck open. Take it apart and clean.

jb

 

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