Tw-5 Hydraulic pressure.

[Daniel in PA]

Good morning. My TW-5 loader function seems lethargic when lifting heavy loads, bucket full of stone, also won t lift front of tractor. Allied 795 with 8 foot bucket. I will attach photos of how it s plumbed. I have a service manual for the TW and 30 series that covers a lot and some things posted on hear don t agree with my manual when compared to a strictly TW manual, pressures sometimes don t agree. I have checked pressure at one of the remotes and get 2400 @ pto rpm speed. I have read the theory of operation and don t quite understand the pilot circuit, the control valve for the loader does have the third hose and it plumbed into the pilot line. If my pressure readings are correct, maybe I have a problem in the loader valve it self. This tractor is used for lane maintenance so I haven t used any of the remotes, use an 8 blade on three point with no complaints on function there. Tractor shows 3250 hrs which I have no reason to think is not correct, I replaced the original rear tires. Any suggestions?
Thanks in advance.

 

[Daniel in PA]

Should have added it has dual pumps and deluxe remotes. Manufactured 4/86

 

[Bern]

You have a later TW tractor with closed center remotes. If you're using the repair manual, follow the troubleshooting steps
for the 8030 series tractors and not the TW series.

First thing I'd do is a flow and pressure test from one of the tractor remotes to isolate whether the problem is in the
tractor or the loader valve. My bet is that your problem is with the tractor. Once you've done that, get back to us.

 

[Daniel in PA]

Will do, I have a pressure gauge, need to research to come up with a flow gauge. Thanks

 

[Daniel in PA]

Bern, thanks for taking the time to help me. I m using the combined manual ( see photo). In this manual there are some sections that differentiate between TW and 30 series but the Hydraulic system section is just prior and post April 1985 so I m going by post. I have read the chapter on troubleshooting and pressure testing and there is nothing about a flow test that I can find. I did the pressure test as illustrated and got 2400 @ 1400 rpm s. It states if you can t make 2500 add relief valve shims and if they are at max thickness then it s the safety valve. I m not sure if there is a way to rule out the safety valve but removal is beyond my ability because of cab removal. Could the relief valve spring be weak, perhaps replacement? The pressure is close but not quite there, maybe the cheap Chinese gage I use. Good quality oil and new filters. Perhaps you could advise me on flow test.

 

[Daniel in PA]

 

[Daniel in PA]

 

[Bern]

There seems to be no mention of a combined pressure and flow test in the service manual. Ford's troubleshooting sections always left a little to be desired.

Pressure and flow testing is done with a tool similar to the one shown in the link below. That particular one is for testing power steering pumps and is not big enough for what you need to do. You need to be looking for a 0-30 GPM unit. Given the cost of a unit like this it would likely not be cost effective for you to buy one of these testers for a one-off project like this. Suggest hiring someone with a similar tool to come out and do the test for you.

The tester puts a load on the system by cranking down on the knob which creates resistance to flow. A good pump will maintain 85-90% of the flow at 2000 PSI backpressure as compared to the flow at 0 PSI backpressure. One thing you're looking for during a test like this is how well it performs with cold oil versus hot oil. If it passes with cold oil but not hot oil, this usually means worn pump(s).

I can tell you from personal experience that you're most likely dealing with either contamination in the combining valve spool in the priority pack, and/or worn pumps. However don't jump to conclusions until you do some testing. I would not be wasting time trying to shim the main relief valve.
Pressure/flow tester

 

[Daniel in PA]

Bern, thanks for the in-depth expansion and guidance, I understand now how that would be a valuable test. Agreed, after a cursory search they do seem to be cost prohibitive. I will try to find a rolling mechanic, may have to live with it. For those reading that may be for hire, I and in south west Fulton County Pennsylvania, fifteenth minutes off MD68

 

[RodinNS]

I'd do a couple things since you don't have a hydra-analyzer. Check the pressures cold and again hot. If there's any appreciable
difference I'd be looking towards a bad pump.
The other thing to check... you mention checking pressure at the remote? I would tee into the loader lift circuit (or loader
valve supply circuit) that is giving you problems and see what pressure that is making directly compared to the remote.
Basically, if you have a bad o-ring on a shuttle in the load sense circuit of the loader valve, it can and will limit working
pressure by bleeding load sense pressure.
The pressure you're listing is marginal. I'd rather see it at 2550-2750 if the pumps are sharp... but usually a worn out pump
will be under 2000.
The usual problem of dirt in the load sense circuit generally presents itself as a dead system and nothing works. You have a
working but lazy system.
My first bet would be the pumps... but if the hours are correct, that's not a lot either.

Rod

 

[Daniel in PA]

Rod, thanks for the reply. The tractor doesn t get used for more than an hour or so at a time at mid range RPM s so the hydraulic oil doesn t get rocket hot but I seems that be no difference hot or cold. I had the same thought about teeing pressure gauge in loader boom lift circuit and checking pressure while working that cylinder. Fall projects/fire wood have pushed this issue back, I will update when I have more.

 

[Daniel in PA]

Had a chance to to look into this and without proper tools I thought a good place to start would be to read and try to understand how the system works. I ran into a head scratcher when I tried to find the exploded view of the priority pack at both Messick s and CNH. Diagram 05K01 refers you to 05Q01 and that assembly doesn t look right and it called an unloader valve, but mounts in the same place. Where can I find a diagram of the priority pack. Attached is the illustration from my service manual that matches what I have. Thanks

 

[Daniel in PA]

After more studies, I determined the the diagram is correct, it s called something different than my service manual and it s not illuminated very well. I found two older threads, with comments by Bern and Rod about cleaning the combining/sequencing valve, my book calls it the unloader valve but I see the ball in the spool that they say may need cleaned. Now to determine if this can be done with the priority pack still on tractor or if I have to remove it.

 

[chevytaHOE5674]

(quoted from post at 04:19:54 10/23/23) After more studies, I determined the the diagram is correct, it s called something different than my service manual and it s not illuminated very well. I found two older threads, with comments by Bern and Rod about cleaning the combining/sequencing valve, my book calls it the unloader valve but I see the ball in the spool that they say may need cleaned. Now to determine if this can be done with the priority pack still on tractor or if I have to remove it.

It can be removed with the pack still on the tractor. But it isn't easy. Stand on the head in the cab with a wrench and do some cussing. Haha

 

[Daniel in PA]

Thanks for that advice, I was wondering if the shifter was going to be in the way. I have repaired other things through that cab floor excess hole, hard to figure out what to do with my 6 2"body.

 

[Daniel in PA]

Trying to figure out how all the valves work and what they do, the service manual doesn t explain this one circled in attach photo. It is in what they call the "pump cover plate assembly". Can someone till me what it s called, what it does. As always, thanks.

Update: after further thought I believe that is the pressure relief valve, the one you can shim.

This post was edited by Daniel in PA on 10/26/2023 at 02:55 pm.

 

[RodinNS]

That would appear to be the main pump unload valve but the diagram is too pixilated for me to see completly. Basically the
system has a main pump relief in the main pump body, then supply oil goes up to the lift cover into the priority pack. From
there is crosses the main pump unload valve. When load sense oil is supplied from the remotes or hitch it closes to supply oil.
Otherwise it dumps oil to sump. If the hitch demands oil it goes across the feathering valve. If the remotes demand oil it goes
directly to the combining valve.

The combining/sequencing valve combines the flow of both pumps... so it unloads the engine pump and also acts as a load sense
for the remote circuit only. In that capacity it also acts as the ONLY relief for the engine pump and a circuit relief for the
remotes. It is the left most valve (ahead of the supply pipe for the remotes). The load sense line goes into the pack on the
mid/forward side of that valve.
The other valves in the pack are a feathering valve for the hitch and the unload valve for the main pump. I don't recall now
which is which...

Back to the combining/sequencing valve. It can be removed through either port on it's body... so through the front plug, if you
have 4-5 of forward clearance. It's under significant spring pressure so be careful. There's also a small filter screen in
there to filter the load sense oil. When you remove the valve spool you will find a set screw in the end. Inside the spool is
another spring and check ball and retainer. I just scribe the spool and plug, then screw it out, counting the turns... Take the
whole thing apart, clean in solvent, oil and reinstall.
Just find the source of the dirt, change the oil, etc.

I still think you will find your problem in a shuttle o-ring in your loader valve. Or a weak pump.

Rod

 

[Daniel in PA]

Rod, thanks for the in-depth explanation, very helpful. Still planning on taking your original advice and testing one of the cylinder lines for pressure under load, need to get a tee and some fittings.

 

[RodinNS]

Was just thinking again... you could put your gauge in the remote and tie it off (dead head). Then operate the loader and see what
residual pressure is there. May not be perfect but give you better info than you have for a quick and dirty.

Rod

 

[Daniel in PA]

Rod, great idea, I had the same thought and ordered a 1/2 pioneer female coupler to mount on my gauge last night. My loader break out numbers are based on 2500 psi, see what I get. After thinking about the system the problem could be the pump or pumps but it seems it could also be pressure loss in other places even one or more of the remotes leaking past to return side. Depending on what I get at the loader cylinder disconnect I may disconnect main loader lines from remote circuit and plug, then retest the pressure at a remote. I m not trying to deny that it could be a pump but I think some isolated would be the first step. One thing I neglected to mention is that when I test all 4 remotes I got different reading at each one, one didn t show any pressure so there s something going on there. Thanks for the help