Help! V452t wheel loader - loss of hyd functions

[high_lux]

Hi there,
We have a giant v452t wheel loader. It has basically lost steering and hyd boom up / tilt functions etc - it tries and can move those cylinders slightly but has no power. Steering is difficult and slow, It won’t lift the boom even at full throttle - can use tilt slightly, can use 3rd and 4th function but they are small cylinders and are definitely slower / no power. It has a gear pump that directly feeds the steering orbital valve and then from what I can gather is sends excess oil to the control valve for the joystick as 2nd priority (boom up / tilt / 3rd & 4th function etc). My thinking is the gear pump is poked as I don’t have steering either or is there a possibility the orbital valve is faulty? I removed the tank return line from the orbital valve and oil did come out when I started the engine briefly but I believe it should do that anyway? It would be difficult to plumb in a pressure or flow gauge on the machine because it has metric fittings (not very common here at all) and it’s also very tight and hard to access anything.
Is there another way I can test or try to diagnose what is at fault? The pump gets warm quickly when I boom up or down for say 30 seconds hence my thinking the pump is leaking / worn internally. I’ve attached the schematic for reference.

 

[Coaldust]

Welcome to the HEF, fellow wheel loader enthusiast. Glad to have you.

The most important thing to remember, in this particular situation, is to not panic. We got to hold it together, man.

If we can do that, and keep out wits, we should first pull the suction filters and take a look see.

 

[high_lux]

Thank you
The suction filters had a bit of debris on them including a few very fine metal particles which is probably of a concern, Also the oil was quite dirty particularly at bottom of the tank with the suction filters (there are left and right tanks - joined) it had almost a thin layer of grey paste at the bottom. IMO the suction screens were not clogged enough that I would think they would be restricting suction at all. The smaller one being the worst though.

 

[Nige]

Is that the remains of the oil that you drained from the tank on the suction screens as indicated by the arrows.?
If so the oil appears to be contaminated with water, and pumps like the variable displacement one shown on the schematic you posted above in general do not like water.

 

[Vetech63]

Does the transmission go into gear and move the machine? I’m wondering about the drive on the engine flywheel

 

[Coaldust]

Is the metal in the screens ferrous or nonferrous? Both?

 

[high_lux]

Is that the remains of the oil that you drained from the tank on the suction screens as indicated by the arrows.?
If so the oil appears to be contaminated with water, and pumps like the variable displacement one shown on the schematic you posted above in general do not like water.


No that is the material that the screen is made up of, probably like a hard resin that the metal screen is set in to when it is made?
The VDP appears to work fine still…it drives the hydrostatic trans drive

View attachment 278226

 

[high_lux]

Does the transmission go into gear and move the machine? I’m wondering about the drive on the engine flywheel

Yes drives fine. The VDP drives the hydrostatic drive so it is the front pump closet to the engine. The middle pump and / or circuit is playing up. The last pump/circuit appears to work fine too - (drives the continuous flow and inching pedal)

 

[high_lux]

Is the metal in the screens ferrous or nonferrous? Both?

Hard to tell I guess and I’m not too sure? Could go and have the oil tested but probably show up dirt / silica etc now anyway. Majority of what you see in the dirty screens photo is more of like a pasty type sludge.