450B hydrolic problem (backhoe)

[vestor_guy]

Before you tear into the backhoe control valves, you need to solve the problem of the system being at high pressure and loading the engine. It is an open center system so a load is only placed on the pump if a valve is closed somewhere in the circuit. Each of those valves has its own pressure relief valve and you can hear the squeal from the relief valve when they are operating. Somewhere, you have a partial blockage of some sort.

[JD430C]

Check the pressure and return lines going from the crawler to the backhoe. Neighbor has a 1010 that did the same thing this spring. Engine would load up, but would act normal while running the loader. Backhoe wouldnt do anything. The main lines hung down below the belly pan and one collapsed when he ran over a large rock.

Andrew

[aussie dave]

. Each of those valves has its own pressure relief valve and you can hear the squeal from the relief valve when they are operating.

I disconnected the backhoe to eliminate any problems there so I know the problem is in the machine somewhere and not in the backhoe.

I do notice a sound coming from right hand side when I'm sitting on the machine under the lid where my front bucket levers are in front of the Hydrolic tank. It looks like the quick disconnect lines run to this unit and there are a few silver units there that I guessed are solinoids or something?, well there is squeal sound coming from there that go's away when I lift the bucket.

[vestor_guy]

Now you know the problem is right in the area of your lever controls for the bucket and AUX control. There also could be another valve for some control previously installed on the crawler.

See if you can feel which one of the relief valves is screaming. That would be the circuit that has the problem. If there is a solenoid of some sort, that is not a common installation. Anyway, right there, you should find a valve stuck in an actuated position.

[aussie dave]

Ok good, I will investigate further in that area!

Cheers mate


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[JWB Contracting]

Did you connect the two backhoe hoses back together. If you didn't you will here your relief valve upon start up and risk the possibility of blowing up your pump. I am assuming you narrowed it down to your loader machine has the power beyond valve like every other one that I have seen.

Also, the selenoid you see is for the automated return to level function on the bucket curl / dump function. If it is not working like most are, if your bucket control lever is pulled towards you it will lock in the bucket curl position. Make sure you lever is not locked in the curl position. This will cause the same issue as above and may result in you hydraulic pump blowing up.

[aussie dave]

Yes the two hoses are together.

There's no problem with the 4in1


Thanks

[aussie dave]

I think it it the large one marked with a red dot that is making the nosie (they are the relief valves right?) i undone the 4 screws and toke the cap off and inspected but no visable problem

The smaller one on the left gets pretty warm and i can also move the crowd lever a far way until the bucket actually moves and in that space if i hold it there it takes most of the load of the engine


What is the lever for that i put the red circle around?, doesn't seem to do
Anything..


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[vestor_guy]

The circled valve looks like a selector to switch the aux control lever between the 4 in 1 bucket and a ripper or other rear equipment.

The main relief valve is just to to right of the red dot in your picture.

The red dot is on the boom control circuit and the relief valve is just above the control lever attachment point.

I would take a serious look at that valve and see if all the parts are intact and that there is no obstruction in the return path from the valve to the reservoir.

[Tigerhaze]

The circled valve looks like a selector to switch the aux control lever between the 4 in 1 bucket and a ripper or other rear equipment.

That was the diverter valve that I was trying to remember-thanks.

[aussie dave]

I would take a serious look at that valve and see if all the parts are intact and that there is no obstruction in the return path from the valve to the reservoir.

Ok, I'll have a look at that this afternoon and hopefully I find a problem with it!...

I hate having these problems!, I don't mind once I know what the problem is but it's the worry of the unknown and trying to pin point the problem that drives me nuts!. My thing is motorcycles so i don't have much experience with heavy machinery.


Thanks
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[aussie dave]

I had a look at the relief valve and couldn't really see anything to wrong so I pulled it apart cleaned it and put it back however there is a screw behind the 18mm bolt with copper washer and it was wound nearly all the way in and as I wound it out the revs picked up and the black smoke cleared, the machine seems to work fairly fine now however the oil and tank still get fairly hot so I don't know if this has fixed the problem

I found if I wound that screw out to far then the bucket wouldn't lift

[vestor_guy]

The normal operating temp of the oil is 160 degrees F.

I have not had the occasion to disasseble the control valve but once the valves are correctly assembled, the spools are self centering via the spring and two stops on the end of the spool. I am not aware of any adjustment for centering the spool.

As for the bolt on the back of the boom control valve, that is part of the detent assembly and should not be adjustable. It should be installed tight and loctited. If you indeed loosen that bolt, it will change the stop positons by altering the pressure on the spring between the stops.

That valve is obviously causing the system pressue to load and something is not correct with the spring and stop positions that center the spool. That valve also has a detent position when it is fully forward to "float" the boom. Look for anything in that area that is worn or broken.

[aussie dave]

We have a guy that comes and services the loader at my place of work (gunlake concrete) and i phoned him up and asked him a couple of Q's and that afternoon he was kind enough the stop by my place on his way home and have a quick look at the situation, he ran me thru the basics of the hydrolic system and told me a few things to check out and left me with a couple of jobs to do. he spent an hour of his time with me and even till after the sun went down and his wife was ringing him. He asked for no money and i didnt even catch his name!. I better throw him a case of beer tomorow..

Anyway,

I traced the flow of oil thru the system, tested the quick dissconect couplings, traced flow back to the tank looking for any blockage

i found the Quick disconnect couplings may be abit unreliable due to wear and tear, i found they may look / feel connected but not always properly connected.

i also toke off pretty much anything that was easily removable from around the levers and cleaned them and put them back and also disconnected a few hoses in the same area and let some oil blow thru them while disconnected to clear any obstructions.

Strange that the backhoe fixed itself?.. it had oil flowing thru one of the lines without me activating the lever but now its fine..



thanks for all your replies and help. now i have one oily dozer to go clean!


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