460 diesel POWER STEERING ISSUE

I have a 460 diesel that all was working fine and suddenly lost power steering(PS) and hydraulic lift on the tele-depth system. I replaced my hydraulic pump(HP) last year and everything was working fine before just fading and quitting altogether. Since the HP issue, with the help of Pete23 on this forum, I Have since fixed the HP problem. It was a missing o-ring in the check valve system.
So, now I've moved on to determine what the problem is with the PS system as it failed around/at the same time. As I mentioned, I had replaced the HP last year and before I removed the HP, I performed a pressure test on the power steering pump/system by placing a valve on the return line and a gage in the test port to see the pressure produced by closing the valve. When I was closing the valve I remember feeling the flow of the fluid as the pressure went up and felt like if I closed the valve completely that something was going to blow. The pump then produced around 1000psi before I opened the valve back up. I never closed the valve completely.
Now today, I did that same pressure test and did not get the same result. The pump only produced 100psi and I never felt that rush of flow under the valve. My primary question is should I check anything further before I drain the fluid and inspect the pump? And then, what should I look for or inspect on the PS pump itself once I Have it out? This PS pump has run flawlessly since the day I got the Tractor. It has also run well since I replaced the hydraulic pump up until now and I never heard a strange sound or felt anything strange while using the tractor.
If anyone has any further questions please let me know. I am somewhat lost. I'm hoping that tomorrow I can see something obvious once I get the pump out. I do plan to do a flow test before I take The pump out but I don't expect to Have much flow.
PLEASE HELP.
Thanks, Tod.

It's me again. I understood that you had just recently replaced the hydraulic pump that is why I mentioned the o-ring and gasket between pumps. If it was working fine after you replace main pump, I would suspect your power steering pump just took a dump. I just come on here again to say that the power steering pump has it's own built in flow divider and relief valve incorporated right in the pump. There fore you can safely block flow to get full pressure readings. You might be lucky and find some little piece of crap in the relief valve, can't hurt to take it apart once you have pump out. Might even find that o-ring, but it would have to sneak through the filter. On that note, I have seen those filters totally collapse and get a big hole in them letting anyting through but I IH beefed them up many years ago so that should not happen now days. Took a lot of complaining to get their attention on that one though. One thing about most co.s, they don't believe what mechanics tell them, but if customers quit buying then they take heed.

Hi Pete23, I was hoping you would find this new post. Where is that relief valve in the power steering pump and what specifically do You think I should be looking for? I didn't think a PS pump or any hydraulic pump would just go like that. I suppose anything is possible but it always worked so well. I guess I'll find out tomorrow. If you have further suggestions about this internal relief valve, I'd like know more.
Thanks again,
Tod

Depends on which pump you have, the cessna has flow control and relief valve incorporated inside same valve, thompson relief valve is on side of pump and flow control in more integral. At any rate, the relief valve is right in or on the pumps. And oh yes, they can crap out just like that, but remember, you could be loseing flow right through the steering bolster itself, that is why I take the return life off to see if flow just keeps on coming while trying to steer. The flow will continue up to a point but should definetly slow down if the wheels are not turning. I think I might be getting you confused now. I just kind of pick my way through trouble shooting depending on results I get so hard to explain everything.

When i asked the fellow why he did not use his 460 diesel,he said the hyd pump and power steering suddenly quite working.What happned was the gear that drives the pump had come off! Cheap fix and easy?? Bud and Old Stinky!

I understand Pete23. I'm working on some tests right now and will post later this evening. Please check in later and see what happened and if you or anyone can offer any suggestions. I feel like its my first date, just fumbling around not knowing what to do. Lol.
Talk soon,
Tod.

Ok, before I pulled the pump, I decided to do a flow test as someone suggested and I'm so glad I did so I'd like to thank whoever took the time to suggest that to me. I would've lost a bet over whether I had flow or not. I did not expect to see any flow at all but to my surprise, I DO HAVE FLOW out the return line of my power steering line (aprox 1gallon in 20 seconds or so). So I plan to continue with the plan to pull the pump and inspect the overall condition my "Cessna" pump, and make sure that the shaft between the 2 pumps is being turned. Then I plan to inspect the relief valve and hope to find a piece of crud or something stuck or plugged so the pump can't put out more pressure. Can anyone explain how if and when there is a lack of pressure being put out from the PS pump, where does the fluid then go?
Does anyone have any better plan cause I don't know exactly what I'm doin. I did replace the hydraulic pump(HP) last year and everything worked fine even before that with the PS pump. Its just never given me any issues before. I am Thinking that since I have flow through the PS system but no pressure that my pump should still be ok, is that right or not?
I'll be monitoring this post all evening and will respond fairly quickly to anyone who Can help.
PLEASE HELP,
Tod.

If you have flow, the pump is turning... should not be a disconnect between the pumps. You have a problem elsewhere in the system and the most likely suspect is the relief valve has something sticking it open, or a problem in whatever valve controls steering direction. Most of these relief valves are "pilot operated". meaning there is not a main spring controlling the pressure, but a pilot circuit that "feeds back" from the system pressure. Does not take much contaminent to plug them up.
I have worked on a 460U, but as I recall, all I did was change the main pump from the standard 12 gpm to the optional 17 gpm. This was to run a field test at Cessna, running a bush-hog type mower with a high torque hydraulic motor in place of the PTO gearbox.

If I have flow out the PS return line and as someone requested there is an obstruction in the steering bolster or anything between the pump and the obstruction, wouldn't I still show the Max pressure from the pump if I have a pressure gage in the test hole on the manifold plate?
What I'm thinkin is because I can't produce more than 200psi and I seem to have the correct volume of flow(1gallon in aprox 20 seconds) wouldn't this suggest that I Have a relief valve issue rather than a bolster issue or something similar???
Thanks guys,
Tod.

If you have flow out the return port from the bolster and no pressure in the system, there must be a bolster problem. If there is no flow out the reurn port, then it could be dumping over a stuck relief valve... wasn't taking the flow out the bolster return port into consideration in my last reply. If relief was stuck open, I think on those, the flow dumps right back into the inlet port of the pump and you would not have flow through the rest of the system.

OK, If that is the case, then what is the Bolster, where is it located and how can I test it??? What you're saying is I don't need to take the pump out and inspect the relief valve, Right?
Thanks, Tod.

(quoted from post at 08:01:33 06/28/11) OK, If that is the case, then what is the Bolster, where is it located and how can I test it??? What you're saying is I don't need to take the pump out and inspect the relief valve, Right?
Thanks, Tod.

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At this point, it looks to me like the pump and relief valve are eliminated as the problem. As for the bolster, someone more familiar with a Farmall 460, like pete 23, can help. It's the steering column in the front, but I'm not sure how the PS is done in the 460. You have to have some sort of valve to input the direction to turn and that has to work off the input from the steering shaft... may be inside the bolster, but it's there somewhere. Then there has to be some form of power assist, which can be some form of rotary torque generator (like Char-Lynn or Behlen make), or it could be a pair of cylinders, or a single two-way cylinder. My guess is on a Farmall type bolster, it may be a pair of cylinders built into the bolster, but that's just my guess.
I'm not that familiar with the workings of individual tractor models, but my input is from 38 years at Cessna/Eaton, with 25 of that time in the Cessna engineering lab. However, without a hydraulic schematic of the system, it can be hard for me to pin-point problem areas... also been retired for almost 9 years and I've forgotten a lot. Dad had a 460 Farmall that I have used, but never worked on any mechanicals.

Flow under no pressure only really tells you the pump is turning. You need to put it to work, I mean turn steering wheel or even put the pressue gauge in the return line. Like I said before, the relief valve is in pump so you can safely block return.While observeing the flow coming out of return line, turn steering wheel. If front wheels do not turn and flow stays the same that will tell you flow is going right on through bolster valve and cyl. If the flow stops or darn near stops, that tells you it is pump or relief valve. A shot pump will flow almost identical amount of oil with no pressure applied. That is why we flow rate pumps with flow raters and check free flow against flow under pressure. I would sure do more checking on pump part of problem before I got involved with the front bolster.

Thanks Pete23, I'm gonna pull the pump and disassemble the check valve and maybe even split the pumps and make sure what's goin on in there. Maybe before I drain everything I'll disconnect the return line again and see how the wheel turns with the line disconnected and also observe the flow rate while I turn it. So, looks like I have some work to do. Could be worse, it could be snowing!
Tod.

(quoted from post at 12:29:25 06/28/11) Could be worse, it could be snowing!
Tod.

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Or.... you could be in Kansas where it's suppposed to be 104 to 106 the next 2 days . Nice today though, only 84 now.
Pete is giving you practical knowledge from experience with your model... mine is more conjecture from general hydraulic experience... I'd listen to him first.

Thanks IH fan. I appreciate the insight. And the weather
report. We topped out at a balmy 61° today. Unseasonably
low but this year seems to the norm. Not very good for the
corn farmers but this year I have only rye and wheat in the
grounds so wet and cool is what I prefer. Anyway, I got to
watch my granddaughter today so I didn't get a chance to
pull the PS pump but as long as I don't have the grandkids
tomorrow, I will get it pulled for sure.
Tod.

Well, I pulled the pump and replaced the o-rings on the flow control valve sleeve. I really didn't see anything that jumped out at me to help determine what was wrong. The o-rings on the flow control valve sleeve looked worn so I decided to change them but other than the o-rings I didn't notice anything wrong in the relief valve area. So, I completely disassembled the relief valve, cleaned it up, put it all back together, and put the pump back in the tractor. Then when I started the Tractor I did notice a difference but only slightly. The best way I can explain the change is that if I tried to turn the steering wheel quickly, I noticed no difference. If I turned the wheel slowly I noticed more power assist in the steering. I Hope that makes sense. If I turned slowly it would just slowly turn the tires with little effort. If I tried to hurry the turn, I really got no assist.
I really don't know where to go from here, if there is a direction for me to go. I fear that my pump is shot. Is there a single test to determine if my pump is shot? Or a test to show that it is good? I hate to purchase a PS pump and install it only to find out my old pump was still good and have another issue to fix on top of it.
Anybody have any ideas or insight? Have I done all the tests I can do or should do?
Please help,
Tod.

Again, not being familiar with the particular layout of the system, mainly the plumbing, If there is a location in the lines where you can disconnect the line between the pump outlet and any of the steering components, if you have or can find a needle valve to install directly from the pump, and squeeze it down a little at a time to see if it builds pressure, that would tell you what the pump is capable of. Since the relief is built into the outlet of the pump, you will not hurt anything and it will tell you if the pump will supply oil to build pressure. If you are dumping the oil into a bucket from the needle valve, if the pump is working, it should flow up to the point of shutting the valve off completely and should reach system pressure before it's shut completely off. Of course, we had equipment available to do these things and I do not know what you have handy. An external relief valve in place of the needle valve would also do, but you are less likely to have anything like that. At about 3gpm, a 1/4" needle valve rated at 2500psi should do.
pete may know a simpler way to do it, or if there is a place to break into the system like that.

I have a valve in the return line already, just a common valve
that takes 3 full turns to completely shut off. I think its a
common gate style valve. If I can get into the outlet line
before it goes onto any other
steering components, just the steering line, will that
perform the test you are suggesting? It may not be as
precise as a needle valve but wouldn't That complete a pass
or fail test on the pump?
Thanks for the reply
Tod.

I would be careful the valve you use for this is rated for whatever the system relief is set at... if this is 2000psi, I wouldn't use a water system 250psi water system rated gate valve. You might end up with brass pieces in your body parts. I saw an old 9N Ford and loader plumbed with water line and a gate valve to separate it from the 3 point, but I wouldn't like to do it. Be sure you plumb a guage in ahead of the test valve so you know where you are. Only reason to shut it [u:1bd98ad8b6]completely[/u:1bd98ad8b6] off, is to know for sure where the internal relief valve is set.

After i replaced the o-rings on the Flow control valve sleeve, when I was installing it back in the PS pump it went in very tight. Is the flow control valve sleeve supposed to move in any way? Either in and out or spin in place? If it needs to move at all, I will need to get smaller o-rings so it can move.
Just trying to cover all my bases. Also, I will be doing the suggested pressure test later, I need to go get a higher pressure rated valve.
Thanks again,
Tod.

(quoted from post at 10:45:46 06/30/11) After i replaced the o-rings on the Flow control valve sleeve, when I was installing it back in the PS pump it went in very tight. Is the flow control valve sleeve supposed to move in any way? Either in and out or spin in place? If it needs to move at all, I will need to get smaller o-rings so it can move.
Just trying to cover all my bases. Also, I will be doing the suggested pressure test later, I need to go get a higher pressure rated valve.
Thanks again,
Tod.

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No, I don't think it moves once in place... as I recall, all the relief valve workings are all internal. Some of those valves were crimped so they are not repairable, but some are held together with an internal snap ring and can be dis-assembled. Most of the older ones were this way and I am just guessing, but I'd say this model is most likely that way. Most of the technicians and engineers I knew that worked on these are dead now, so I don't know who I would ask. A dealer's technician would be your best bet. If you take it apart yourself, do it in a clean location where any small parts like springs, shims, orfice plates, etc. will not get lost.
Did you find a way to isolate the pump/relief from the rest of the system?

I don't think isolating the relief from the rest of the PS system is possible at all. It is a Cessna pump and the relief valve is built right in the pump itself. I don't know if it would work but my only thought is to remove all the internal relief valve parts and do the test with all the relief parts laying on the bench. But, I'm not sure if doing that would give me full pressure or no pressure. What do you think?
Tod

(quoted from post at 11:19:37 06/30/11) I don't think isolating the relief from the rest of the PS system is possible at all. It is a Cessna pump and the relief valve is built right in the pump itself. I don't know if it would work but my only thought is to remove all the internal relief valve parts and do the test with all the relief parts laying on the bench. But, I'm not sure if doing that would give me full pressure or no pressure. What do you think?
Tod

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I did not mean to separate the relief from the pump. I meant to separate the [u:5a0caf3983]pump/relief assembly[/u:5a0caf3983] from the rest of the PS system, ie; the bolster. There has to be an external pressure line running from the belly mounted pump to the bolster and [u:5a0caf3983]this is where you need to check it[/u:5a0caf3983]. You will be checking [u:5a0caf3983]both[/u:5a0caf3983] the pump and relief, but if you have flow and it continues as you build pressure by squeezing it off with a valve, the pump/relief is fine and your problem is "downsteam" of them, meaning somewhere in the bolster. As I mentioned before, there has to be some form of directional control valve on the input to the bolster. Not being familiar with the model, it may be external or internal to the bolster, and then the cylinder(s) to rotate the output, the vertical shaft down to the front wheels. To use the Char-Lynn as an example, the input shaft rotates very slightly and the output lags slightly... this is where the directional control valve is "doing it's thing" of telling the wheels which way to turn. Same thing has to happen with this... there has to be a directional valve controlling when and the direction to turn. Now, since you say if you turn it slow, there seems to be some power to the steering, it seems to know which way you are turning the wheel, but may be leaking in that area and not building enough pressure.
Some people think the relief valve is "creating" the pressure... it is not, the load it takes to turn the output shaft to the wheels "creates" the pressure, the relief valve only limits the pressure. since the rellief valve does not relieve the pressure externally from the belly reservoir, it will be hard to know for certain if the relief or the pump is bad, but you will isolate the problem to that assembly.

IH fan, I sort of understand what you mean. To be honest I
had to read it a few times but I sort of get what you're
saying. I guess I want to just take this one step at a time. I
am going to disconnect the pressure line going from the
pump to the front end and get a valve in there somehow.
Then run the tractor and after its warmed up a bit I'll close
the valve and see how much pressure I get. Then I'll post the
results and see where to go from there. I do have a
hydraulic system book/manual but it doesn't troubleshoot
the PS system very well. I'm gonna check another manual
tomorrow n see if that one can help me. Not that you aren't
helping me, but I like to understand what I'm doing. Be
patient with me, I will get it. Thanks for all your help IH Fan.
Tod.