450B hydrolic problem (backhoe)

[aussie dave]

G'day,

I have an old 450B on the weekend i was using it and got a small leak from a hose on the backhoe (picutred marked red dot) but kept working as i was only using the 4in1 on the front and not the backhoe, then about 1/2 hour later the line blew off on the backhoe and oil sprayed out under alot of presure.

I reconnected the hose on the backhoe but then nothing on the backhoe worked!, the legs didnt go up or down and the bucket wouldnt move or swing L/R, (the 4in1 still worked fine) however when i disconnected one end of the hose and faced it into an empty drum, oil would flow out upon start up of the machine and the legs would go up/down and everything would work again but when i reconnected the hose nothing on the backhoe worked again.

i also noted that when the hose is connected the machine wont move forward as quick however if i raise the 4in1 while driving forward the machine moves abit quicker?..

(simular machine)

- Should oil be flowing out of this line (when disconnected) upon start up without moving the lever ? ? ?



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[aussie dave]

Actual Machine

[vestor_guy]

The 450 hydraulic system is open center. You should not be getting pressure to the crowd cylinder unless you have opened the control lever.

You should check the control levers for the hoe. One maybe stuck open and you are not getting power beyond that circuit.

[Tigerhaze]

I may not be right about this, but doesn't the 450B have a diverter valve ("power beyond" valve) that allows the use of either the front-mounted hydraulics (i.e. 4 in 1) or rear-mounted equipment (i.e. backhoe)? I thought you had to switch the valve for one or the other, but couldn't operate both at the same time. Could this be an issue?

[aussie dave]

Thanks for your reply but i found these quotes and have a couple of Qs..

Your machine has an "open center" hydraulic system meaning that the hydraulic fluid circulates constantly whenever the engine/pump is running."

- so I need to push the lever to make the oil come out of that hose right?


"If you have a power beyond fitting in your loader valve, then the output of that fitting MUST have a clear return to the hydraulic tank. If it has a hose that is open, it will pump 23 gpm of hydraulic fluid out of it "

- what is a power beyond fitting?
- what is s Loader valve?

[aussie dave]

I thought you had to switch the valve for one or the other, but couldn't operate both at the same time. Could this be an issue?

Hi, just seen your post. I can operate both at the same time on my machine

[Tigerhaze]

Hi Dave-

Unfortunately I cannot acces the photos at work due to internet blocking. That might help me understand a little better-not your fault though.

The loader valve is the hydraulic valve block under the "control box" that is attached to your loader operation lever. The 4 in 1 bucket should also tap into that valve block under the box. The backhoe should be attached by quick disconnect couplings at the rear of the machine and is also part of the loader hydraulic system. Using the 4 in 1 bucket is reducing the volume of oil in the system and would affect backhoe operation. I thought you could only use one or the other with a manual diverter valve to switch between one or the other but I'm apparently mistaken.

The hydraulics for your loader/4 in 1/backhoe are a separate system from your HLR transmission so using the loader system shouldn't affect the speed of the crawler.

[aussie dave]

. The backhoe should be attached by quick disconnect couplings at the rear of the machine and is also part of the loader hydraulic system.

The hydraulics for your loader/4 in 1/backhoe are a separate system from your HLR transmission so using the loader system shouldn't affect the speed of the crawler.

It appears to have two large "quick disconnect couplings"

Using the 4in1 may not effect the speed but defiantly sounds as though it's taking abit of strain off the machine.

It's odd that with the hose connected noting works but when I disconnect it I get a response from the backhoe.

[vestor_guy]

It almost sounds like the return quick disconnect is blocked or not working. That would explain why the engine is loaded all the time from the hydraulics being up against the relief valve pressure.

[aussie dave]

The 450 hydraulic system is open center. You should not be getting pressure to the crowd cylinder unless you have opened the control lever.

You should check the control levers for the hoe. One maybe stuck open and you are not getting power beyond that circuit.

Turns out you are on the money old mate


tonight i had another look at the machine after keeping an eye on your replies on my phone at work today


i disconnected one end of the hose and faced it down into an empty drum then turn the machine on and it started filling the drum. i tried the lever forwards and backwards and it was blasting the oil out like crazy!, i found that there is no neutral position in the lever where the flow stops!, so its constantly flowing so thsts where the problem is!.

Just to test the theory i disconected the hoses off one of the legs and it would only shoot out oil if i hit the lever.


This is the problem lever;

doesnt seem to be any adjustment that i can make to the unit at first glance.

What do i need to do now?


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[LeonardL]

Take the valve apart and look for a broken spool. If you don't have any control at all with this particular circuit, then I would suspect a broken valve spool. This is what is allowing the flow of oil through the valve and out through the hose.

[aussie dave]

Ok cool

Are each of this 6 valves separate units or are they all joined together as one bank?

You wouldn't happen to know off the top of your head how they are bolted in ?, just to give me an idea what I'm up for when I get home ?

[LeonardL]

Your control valve is what is known as a "Stack" valve. In other words there are several valves all stacked together. There will be at least three (3) bolts or long studs with nuts that hold it all together. Some systems have as many as six (6) bolts or studs. If memory serves me correctly there will be no more than four (4) on your particular system. There will be O-rings in between each individual valve and also on the end caps. The O-rings are also a possibility for your problem although I doubt it. If an O-ring is bad it will usually just leak around the stack of valves. I still think you will either find a broken spool or a component attached to the spool has come undone. I hope this helps!

[aussie dave]

Thanks for all the info

Hopefully I'll have enough daylight to have a play about with the it this Arvo.

Thanks fellas

[aussie dave]

It almost sounds like the return quick disconnect is blocked or not working. That would explain why the engine is loaded all the time from the hydraulics being up against the relief valve pressure.

That is the problem i have now.
I disconected the backhoe, checked and cleaned the quick disconect couplings and reconected them by-passing the backhoe for now (while i work on the control valve)and i still have the same problem of having load on the engine

It definatly sounds & performs like the engine is under load however raising and lowering the bucket takes the strain off the engine.

Any further clues


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