I have a JD 490D that is experiencing a travel issue. I believe I have a bad or malfunctioning relief valve. When you use any function but the tracks, the machine works fine. When you go to travel, if you press down very quickly on the travel pedals, the machine loses one side of the hydraulic functions. I assume that there are reliefs on all the hydraulic circuits. My question is, can someone tell me which ones are related to travel and where they would be located? I would like to swap the two sides and see if the problem moves. If so, I know which one is need of replacement. When I lose one side, I can shut the machine off for a minute or two and restart and everything goes back to working. Makes me think I have a weak or broken spring in a relief?? Any help or input would be appreciated. Dave
Does it mistrack while propelling and operating a function at the same time? Does it stop completely? What hydraulic functions are you losing? Travel reliefs are on the travel motors.
When it happens, I lose everything on one side. Say one track , and everything associated with the stick on that side. The other side operates fine. I can shut off the engine and let it sit for a couple minutes, start it up and everything works. As long as I ease ever so gently into the track controls, the machine will work for hours. But if I ever get heavy on the pedal, I lose that side.
It is always on the same side. I lose the right track and the swing and I believe the bucket control. It never swaps sides.
If you move just the left track quickly it will still operate OK? Then if you move just the right track quickly it will stop? Or do you have to move both travels at the same time to make it happen? Just for reference the front pump supplies oil to the right track, bucket, boom 1, and arm 2 spools. Rear pump supplies oil to the left track, auxiliary, boom 2, arm 1, and swing spools. Usually if you lose hydraulics from a particular side it affects the spools in that side only.
I need more clarification! LOL So.....when this machine loses its side when you hit the travel too hard, do the hydraulics return to normal when the travel levers are back to neutral? …..or is the hydraulics on said side gone until you shut the machine off and restart? I'm not going to be much help as I'm not familiar with this machine, but I want to understand the parameters here in case I run into this in the future.
Mg...I may have the wrong functions. It has been a few days since I ran the machine. It does appear to affect everything associated with one side of the pump. If I ease down on the pedals, it will function normally. If I happen to get a heavy foot on the travel pedals, it will immediately kill all the functions on one side. I can stob the boom and raise the track off the ground and it does not seem to affect it. Only with the weight of the machine does it kill the hydraulics on that side.
Like Vetech asked, does it return to normal after letting the travel levers back to neutral? Or do you have to cycle the key switch to bring it back to normal? Having looked at the schematic the 490D, unlike other excavators, has a separate propel relief (it still has crossover reliefs mounted on the motors). It should be on the bottom of the control valve towards the front, left half, sticking straight down (item A). Time to have pressures checked. Propel obviously as well as system pressure, pilot pressure and control pressures to ensure everything is working as it should. Propel relief valve part numbers are 0304970 for s/n 014960 and down, or 0357603 for s/n 014961 and up (if they are available) if you want to try a propel relief valve.
MG....you have to shut off the engine to get whatever is relieving to re-seat. It seems that once it relieves, it can't overcome system pressure to re-seat. That is what had me thinking it was probably a relief valve that was either damaged or worn out. Once the machine loses operation on the things that don't work, just letting it sit there running makes no difference. If it is the propel relief, I should be able to swap them and the issue should swap sides. Is that correct?
If it was a relief valve problem on the travel circuit it should not affect the other functions. Maybe a main relief but Iam leaning something with the pump going on
Dave, my only reservation with it being a pump problem is that if you walk the machine to a spot and stop it and just sit there and work all the other functions, it will operate flawlessly all day without interruption. But you go to move it and get heavy on the travel pedal, and it will lose half of the hydraulic functions. If you go easy on the travel, you never have a problem. If it were a pump problem, I would assume it would show up with other functions. You can just hold the levers for the boom, crowder, or bucket against their hard stops and you can hear it load the engine a bit but it doesn't affect the hydraulics.
OK but if it is a travel relief the other functions should go back to working after you release the travel control because the travel relief is no longer pressurized
I would agree with Dave. When the travel functions are released the dig functions should work. When you are just digging the pump pressure is working on the ends of both the travel and propel reliefs at the same time so if there was a relief issue it should show up during digging (the propel is set higher than the main). The main relief is removed from the circuit by a selector valve when a travel function is activated. I still think pressure and flow tests need to be performed to reach a viable conclusion.
Dave & Mg.....What is the best way to check the pressures. I am sure I can rig up a couple of gauges. Flow may be a bit more of a problem.
When diagnosing hydraulic problems, I usually check the pump flow first...……..bad pump flow can create inaccurate pressure readings. MG could get you the flow specs (usually its a set rpm, pressure rating, and gpm's at set ratings, at operating temp.) Flow meters are expensive so you buying one wouldn't be an option unless you did hydraulic repairs for a living. As bad as I hate to say it, you really need someone to hook up a flow meter first and make sure your pumps are capable of the operations that are required of them. Yeah, it may cost you some money, but what you will save in time and frustration would be well worth it. I'm only saying this because I myself have chased my tail with bad pressures from a faulty pump. (Exactly why I bought a flow meter over 25 years ago )
I'm not against buying a flow meter. I just need to know the max flow so I can make sure to buy one that wiill cover it. I have a couple of excavators, a dozer, backhoe and tractors, so I can probably justify one. Plus I have a couple of good friends that work for ag equipment companies. May be able to "after hours" one.....lol
If you get a good one, it will have several flow ratings that are selectable. I believe mine goes from 5 gpm up to 60 gpm. If you can afford it, make sure to get one that will do 5000 psi working pressure.
I have looked at a couple that are just inline flow meters. They will handle 6000psi and flow of 0-60 gpm. I do believe my bud at the CaseIH place has one. It is just going to be a nightmare figuring out the fittings! Almost everything on that machine is a split flange oil ring style.
Here is the flow specs.
Here is the pressure specs.
MG THA MAN!
You should be able to check the flow by doing cycle times. It sounds like a pump regulator problem.