446 has no hydraulics!

[RoamingGnome]

Just to back up a step... the original problem was no hyd - no drive + no attachment lift (suspected no flow)
the pump was changed and still no flow...

I would be tempted to check the old pump now that it's out of the machine - you should be able to turn the pump by hand, cover the inlet port with your hand and feel some suction... my initial guess would be something maybe stuck in the relief valve allowing all the flow to just return to tank.

See if you can find an online service manual for your machine and look through the hydraulic system... I quickly looked in the technical section here but could only find a Hyd troubleshooting guide... https://manuals.ccigt.com/ServiceManual ... marked.pdf

[propane1]

Well. It sounds like the trouble happened all of a sudden with the original pump. So the second pump is not the trouble. The drive system is not the trouble, because the lift cylinder doesn’t work either. So, in my mind there is a blockage some where, that happened all of a sudden.
I’m still just guessing. Looking in the tank to see oil flow is the first thing to do.
Does this tractor have the hill holding valve, can’t remember name of it, or the flow control valve ?
Maybe the flow control valve got into the, no flow position by accident. If it has a no flow position. I don’t know anything about those valves. Just a guess again.

Noel

[Harry]

I’m with you Noel. Sounds like a problem before the new pump. Possibly there was nothing wrong with the old pump. Thinking out loud here, a test station to hook up a pump and test the flow would be nice. Harry

[Eugen]

Like @RoamingGnome says, you will feel suction on your thumb if you turn the pump by hand. I also test it by pouring some 15w40 oil in the inlet and turning it by hand and covering the outlet. Even a tired pump will create enough pressure to push the oil past your thumb.

Hey all, if anything is so stuck anywhere along the circuit that it does not allow the pump to push oil the engine dies immediately. Those of you who have the hydraulic PTO will have noticed how you cannot start the engine even if you have quick attach fittings on the PTO, and if you don't have the hose to loop the hydraulic PTO, and if the lever is not in the middle. Many a times my kids slipped the PTO lever to one side and I was stumped as to why the tractor isn't starting.

[RoamingGnome]

I’m with you Noel. Sounds like a problem before the new pump. Possibly there was nothing wrong with the old pump. Thinking out loud here, a test station to hook up a pump and test the flow would be nice. Harry

for a simple test of the original pump - you could put it on the bench with the inlet port facing up, - pour some oil into the inlet port and turn the pump shaft - oil should disappear into the pump and come out the outlet port on the bottom...

Big failures like a pump or motor grenading generally cause some (lots of) noise... and give some warning signs before total failure - a broken spring on a relief valve or a relief valve stuck open could cause sudden loss of pressure with very little noise or warning...

[metalguy]

I am suspecting the relief valve. You guys are awesome! I'll first see if there is movement in the tank while running, then look into the relief. I have complete service manuals for the tractor, so that should help a lot. I really want to get this tractor back to running, and kicking butt again. My little 130 has been doing the mowing duties, and it needs to rest. -----Metalguy

[metalguy]

There is no movement in the tank that I can tell. I have it about half full, but it isn't going down, so it should be ok for tests. After looking at the TCV, how the heck do you get at the pressure relief valve with it in the tractor? It looks like it has to be pulled to get at it? It is the one under the large hex cap, correct? The diagram looks to be a ball seat affair, so not much to the actual valve itself. It is getting to it that seems like the tough part. I suppose I can lift the front of the tractor up and get at it that way best.---------Metalguy

[Harry]

You are correct metalguy, it’s a bugger getting in there to adjust the relief valve. I do mine on the lift so I don’t have to get up and down so much. Take your time and it will be easy. Harry

[DavidBarkey]

There is no movement in the tank that I can tell. I have it about half full, but it isn't going down, so it should be ok for tests. After looking at the TCV, how the heck do you get at the pressure relief valve with it in the tractor? It looks like it has to be pulled to get at it? It is the one under the large hex cap, correct? The diagram looks to be a ball seat affair, so not much to the actual valve itself. It is getting to it that seems like the tough part. I suppose I can lift the front of the tractor up and get at it that way best.---------Metalguy

If there is no movement in the tank , it is not the releaf valve . If it was stuck open you would have flow and see movement in the tank . If it was stuck closed you would blow a seal when dead heading cylinder .
The problem has to be at the pump . Possible air lock and not priming . I still question if the original pump was bad . Did you do this test , ? Quote
for a simple test of the original pump - you could put it on the bench with the inlet port facing up, - pour some oil into the inlet port and turn the pump shaft - oil should disappear into the pump and come out the outlet port on the bottom... Quote
How was the pump key in the old pump ?
Did you take the old pump apart to see if it failed and ejected it inners into the system ?
Did you remove the dust seal from the inlet of the new pump before installing ?
Something does not add up .

[thebuildist]

When you changed out the pump, did you drain the tank first? If so how did you drain it?

The reason I'm asking is, it's hard to imagine the return line being plugged on the way back to the tank. Because that would develop so much back pressure that a line would blow or you wouldn't be able to start the tractor.

But if the suction/supply line that feeds the inlet of the pump were blocked, then the pump would happily spin but there'd be no fluid movement whatsoever.

Now it will destroy your pump if that happens in general terms. So I don't mean to say that all is well. But it is possible for that line to get plugged either the line or the bottom of the tank...

And that would give you these symptoms: no hydraulics whatsoever.

So if you remove the feed line to the pump the tank should just drain its oil all over the ground. Right? Would yours do that right now?

Bob