John Deere 490D problem

[heyu29h]

We have a JD 490D, thats driving me nuts!!!!

In order to get any power to the right track, boom up/down, or bucket functions, we have to move the arm, swing, or left track slightly.

At first i thought one side of the pump was going bad, so we got some longer lines and connected, the front pumps pressure hose, and displacement control hose, to the rear pump, and the rear pumps lines to the front pump. This had no effect.

So next I thought, posibly the pump was not getting the signal to stroke, so after talking to a guy at deere, he sugested to disconnect the control lines to the pump, which he says will put the pumps at full stroke. I did this, and with the control lines disconnected ran the machien, and still had the same problem.

Now I am guessing my problem is in the main control valve, but after studing the hydrolic schmatics, im still stumped.

The wierd thing is when i slightly engage arm in or out while pressing the boom down, there is ample power to lift the machien off the ground, but if you dont engage arm in or out slighly, the boom will go down to the point it touches the ground and just sit there, with out even laboring the engine, but slightly engage arm in or out and bamb, it rases the machien right up off the ground. :Banghead

I would be gratefull for any help in this matter!

 

[machine]

what would a 490D be if it were a Hitachi?

 

[Jam]

Hows it going not too sure if this is any help in your case but i had a similiar problem with a hitachi 2 years ago which turn out to be the dipper ram seal breaking up which jamed a pressure relief valve slightly open and i had to work another circuit at the same time to send pressure down to my track motor.

 

[1stephen]

does this machine have a mechanically controlled pump or is it electrically controlled, you can tell this by looking at the end of the pump and see if it has any electric wires coming from any solenoids also it will have a swash plate angle sensor on the side of the pump.

 

[heyu29h]

it has mechanical pump

the pump is mechanical,
and 490d and hitatich 120 are basicly the same

 

[John C.]

Does your machine have two pumps or just one. I am suspecting that somehow the inside of your valve is letting oil bypass the boom down function and it's going further down stream to the next valve in line. When you operate that valve you are backing up flow and creating pressure to work the boom.

I don't recall those machines having hydraulic load sensing so I don't think you have any compensators that could be stuck open. Check your schematic and see if there is a boom 1 or high spool and a boom 2 spool. Possibly one of those is stuck if you have them.

Does your boom drift down when put in the air with a load on it?

 

[machine]

If a 490D is the same as an EX120 ( EX120-1) There is a check valve in the front section of the control that prevents the pump 1 oil from going into the pump 2 oil passage and then back to tank. When you shift any spool in the pump 2 circuit you are blocking it from going to tank and therefore the functions on pump 1 begin to work ok. On the left side of the front section (closest to cab) about midway up take out the plug which has a spring and
poppet . You may find your problem.

 

[tyler griffin]

I have a hitachi ex120-2 that i have been having hydraulic problems with the machine runs great when cold and tracks great but when it heats up hydraulics get slow and tracking is weak and controls start getting hot

any ideas?

 

[machine]

I have a hitachi ex120-2 that i have been having hydraulic problems with the machine runs great when cold and tracks great but when it heats up hydraulics get slow and tracking is weak and controls start getting hot

any ideas?

The symptom sounds that either the oil cooler is not working as designed. Check that the cold oil bypass valve is in place or that it isn't stuck open.
also check that you are getting enough temperature drop across the cooler core.
If that is ruled out you should be looking for an abnormal amount of heat
being created by a hydraulic component or that there isn't a spool shifted or
partially shifted and causing oil to be going over the relief valves constantly.
The heat you are feeling in the control levers isn't the cause of heat, but likely the result of the oil going to them being hot.

 

[tyler griffin]

is the cold bypass valve in line connected to the oil cooler and how do you check the spools

 

[machine]

is the cold bypass valve in line connected to the oil cooler and how do you check the spools

On the rear of the main control valve there should be a pipe right above the connection of the pump delivery hose that pipe should have the cooler bypass
valve in one end of the pipe. It could be held in by a snap ring. It should also
be about 80 PSI. It will look like a one way check valve be sure to reinstall it
in the correct direction to let the oil get to the tank from the control valve.
To check if there are spools shifted or some other reason the oil can not flow
to tank you can install a pressure gauge of at least 5000 PSI in the pump delivery outlet. Start the machine and heat the oil to operating temp. About
125 degrees Fahrenheit or 50 Celsius.
Install a smaller gauge for more accuracy and with the engine running at high idle with the safety pilot control only in the digging position, the control levers
and pedals in neutral position ,the circulating pressure is in the 42 KGF/CM. or less. Or about 600 PSI or less.

 

[machine]

The valve located in the cooler return pipe is a back pressure valve. It looks about the same as the cooler bypass valve but is much lower in pressure. If they
are interchangeable check that they have not been installed in the wrong places.

 

[tyler griffin]

when you say 600 psi are you talking about pilot pressure or main pump pressure i had gauges plumbed in to the main and pilot pump
Pilot pressure is about 700psi
main pressure is about 5200-5500psi at max digging
I thought that maybe i had a relief valve messing up and would show up on the gauges
the pilot pressure also pluses

 

[tyler griffin]

when you say 600 psi are you talking about pilot pressure or main pump pressure i had gauges plumbed in to the main and pilot pump
Pilot pressure is about 700psi
main pressure is about 5200-5500psi at max digging
I thought that maybe i had a relief valve messing up and would show up on the gauges
the pilot pressure also pluses

 

[machine]

when you say 600 psi are you talking about pilot pressure or main pump pressure i had gauges plumbed in to the main and pilot pump
Pilot pressure is about 700psi
main pressure is about 5200-5500psi at max digging
I thought that maybe i had a relief valve messing up and would show up on the gauges
the pilot pressure also pluses

Your pilot pressure, 700 PSI is ok. The specs. for main pump over relief is 5000 PSI. The surge relief pressure and line relief pressure should be about 250 PSI higher than the main relief. The pulsing in the pilot system is likely the pump solenoids maintaining the pump displacement to what the PVC wants it to be.
Question, what is the main pump circulating PSI with the pilot safety
in the operating position and all hands and feet off the controls and the engine at 2100 RPM?

 

[tyler griffin]

im pretty sure there no pressure until you use a fuction

 

[machine]

im pretty sure there no pressure until you use a fuction

If you are confident that there is no pressure on the 5000 gauge when the oil is still hot install a 1500 PSI and see what the circulating pressure is at full RPM and the safety pilot shut off in the working position. Remember not to touch any functions or your 1500 gauge will become stressed. There has to be some pressure or something is wrong.

 

[tyler griffin]

i will tyr this and let you know what happens

 

[Hitachi120]

I have a 120-3 problem, power to tracks and swing are very weak once it warms up. Motor never bogs or gets a load on it. All the solenoids are unplugged, and when I plug them in the swing and track functions completely stop. 6/7 solenoids have 24 Ohms, one has 68 ohms( right track). On the pump there are 2 solenoids, they have the same resistance and when swapped, no difference. Center joint has new seals, the PVC unit was replaced, and controll valve rebuilt. Is there any way to get codes w/o Dr EX? The hydraulics seem to get hot fast also. In 20 min. of digging the cylinders are hot. Any ideas? I just found the thread for adjusting the angle sensor, I will also try this tomorrow.

 

[bigneal23]

I tried to post a new thread but it wouldn't let me...so I'm trying to post here now...

We have a Hitachi ex160lc-5 and are having some hydraulic problems. It started when we had to replace a line. The line is a metal line that runs from the control valve to the boom lift cyclinders. To remove this line, I had to take aloose the main pressure line coming from the pump to that side of the valve as well as another small line next to the metal line. We got it all put back together and it ran fine for maybe 30 minutes, then some functions started not working. For example it might lift, but not move or only move on one side or swing or not swing. If you shut it down for a few minutes, then run again it would work for a little while longer. It would change what functions worked and didn't work. Finnally now just about every function is moving equally slow...like creeping - the boom will not pick up the machine. I've also noticed that that main pump line I mentioned earlier that I took aloose pulses. It seems to pulse worse when trying to do functions on that side of control valve - boom, arm, and travel (right travel I believe). I have looked through parts, shop, and technical manuals and am stumped right now. Any help would be greatly appreciated.

By the way, I never blend any air out of hydraulic system and wondered if this was necessary?

Thanks