Got the 300u going, but...

I'm still kinda lost as to how the safety regulator detects the valve needs a fluid pressure? I dont know why the valves just dont manually dump the fluid into the res. I mean let's say that you move the valve, there is no pressure going to the valve, so the valve cannot feed pressure to the safety regualtor to open a multipling valve of some sort hence feeding pressure to the valve. I have had it apart, but didnt investigate too deeply into how it works, its hard to follow the passages in the main assembly. I also couldnt get it totally apart, as I didnt have a spanner socket to remove the innards.

Contrary to the information you've received in this thread previously, the 300U did not have an open-center hydraulic system as it came from the factory (what's happened since might have changed that, but probably not). The third, smaller port you've noticed on the side of the reservoir is a control line which handles loading and unloading the hydraulic pump. The actual loading/unloading takes place in one of the valves built into the regulator/safety valve block (inboard-rear valve position, no handle); this block also contains a separate safety valve, and maybe a priority valve (on tractors equipped with factory power stearing only).

As far as your surging problem is concerned, it could be a number of things. Probably the best thing to do at this point is to keep working the system and see if the problem goes away as you get the air out of the system. Since the major thing you've changed, from what I can make out, is to put a filter in the suction line, that's what I'd suspect if your troubles continue . . . perhaps you're not getting adequate flow through the new filter??

Good luck.

I thought i was going crazy when I was recalling that the pump is a demand only system controlled by the safety reg. The reg has 2 "valve chambers" and as you stated one is most likely a regulator valve, and the other loads and unloads the pump. With everyone talking about open center valves, I was getting a little bewildered at what that 3rd port did. The system is calming down and only cycled 2x today. I bled the main lift cylinders by removing them and using the hydraulics to extend them, then with the hose end in the air, and the valve set to dump, pushed the rods back in. I did this 3 times on each arm. No more bouncy loads.

Lets hope that all it was was air in the system. I recall way back when someone wanting to plumb remote valves into the res and someone mentioning theyd have to tape the holes for fittings instead of the oring seal. Well guess what, they are already tapped!! The valve ports are as well. They have a pring or pipe thread design. I dont know what one would do with the 3rd hole in that res cover if they used remote valves.

By chance do you have a "shametic" of sorts for this system so I can better understand it.

The pump still is noisy, which is is expected since theres not much to fix that if the obvious has been address and its still there. It is something I will have to live with until she goes. Ideally, if i was more confortable with the rest of the tractors condition I would spring for a new one.

Maybe you know, but this sound is not as much of a whining as a , well i cant explain it, its not a whining or grinding sound. Besides pump where what could cause this? It is worse with a good load on it. I have a few ideas on what might be the problem besides pump wear.
1. input gear/cam gear wear?
2. oring seals bad in the pump.
I'm not sure if either of this could cause a noisy pump, buit if they could, I'd like to investigate those before I go buying a new pump. I'm not sure what is required for pump removal, I'm sure it involves those nice little gasket things, haha. It's not a major concern, just wanted to get your ideas on it. I will see about borrowing my friends voice recorder to get a few files of sound for you guys to hear so I can get your input. What I'm asking is all pump noise caused from pump wear?
As for the filter, It's rated 25GPM and is a 25micron filter, much better then the brass screen. I could get a 10micron to put on there, but seems it woulkd clogg up faster and restrict flow more easily.
Thanks

On your new filter -- you say it's rated at 25 GPM, but how much pressure drop does this assume? If it's more than a few pounds it could be trouble.

Now if the control valves on your tractor have ported pistons (ie. do not have symmetrical, spool-type pistons), installing a piston rotated 90 deg from where it should be could indeed dead-head the pump when the valve is in neutral.

First thing I'd do is recheck how the control valves are assembled!

I flippin hate the software on this site. So I go to look for the thread about someone telling me that the safety regulator also directs fluid flow to the res when the valves arent in use, but i cant find myy threads, its past past 13, so i go to the archives and sort by author. There is no threads started by me apparently. As you guys no this is far from the truth?
They really must do something about this crappy software, its worthless for reference, as far as I'm concerned bpast page 13 outta be deleted cause people are going to repost questions endlessly cause you can find much of anything in the archives...

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Anyway it sounds as if your hydraulics are somehow plumbed incorrectly.

Your 300U has what’s called an “open center” hydraulic system. When no hydraulic action is required oil flows from the pump to the control valve, passes freely through the control valve and then returns directly to the reservoir. No pressure is developed and the pump runs unloaded.

Now when you move a control valve to extend or retract a cylinder, the control valve redirects flow from the pump to one side of the cylinder and at the same time directs return flow from the opposite end of the cylinder back to the reservoir. The amount of pressure developed at the pump now depends upon the load on the cylinder – the greater the load the higher the pressure.

The relief (or safety) valve is located in the line between the pump and the control valve inlet and monitors pressure in the supply line. It should open ONLY when it’s set pressure is exceeded – for example when the cylinder reaches the stop at end of it’s travel and the control valve is not released, or if the cylinder is overloaded. Otherwise the relief valve should never operate.

(Incidentally when the relief valve operates it develops a tremendous amount of heat. If left to bypass for very long it’ll cause the hydraulic system to overheat….)

Consequently your relief valve opening with the control valve in “neutral” says your plumbing is somehow messed up. Also if your tractor has power steering the flow divider that supplies the steering system may not be working and is constantly restricting pump flow.

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The pulsing of relief valve could be from several causes: The oil level may be too low (pump is sucking air). Could also be an excessive suction side restriction - collapsed suction hose, clogged screen/filter, filter too small for the pump flow. Finally it could be be incorrect (too heavy) oil the system.

Hope this helps, and good luck!

It is my understanding that the safety regulator (i.e. relief valve) has nothing to do with directing flow to the reservoir when the remotes are not being used. The relief valve activates when the pump is deadheaded, and dumps the excess pressure off to the reservoir.

Does your tractor have power steering? If so, it has a priority valve that directs flow to the power steering when it demands pressure. That may be where your problem is.