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Hydraulics with no pressure

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phil fenner

11-04-2002 16:01:34

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After lifting a large log, my 3point will not lift its own weight and no pressure is shown on my guage. Previously completely overhauled. Inspections showed nothing unusual and all appeared very calm in pump cavity. No oil movement around the relief valve. Any ideas?

Phil Fenner

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phil fenner

11-11-2002 20:55:27

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Re: hydraulics with no pressure in reply to phil fenner, 11-04-2002 16:01:34

For those of you that offered suggestions and support, many thanks. The good news is that I found the cause of loss of pressure after the heavy lift load. The bad news is that it is caused by the right valve chamber blowing out a chunk of casting around one of the valve chambers. No evidence of previous crack or void in casting. How did this happen? Can one over torque the clamp bolt which holds the valve assy in place? I used a torque wrench and the book says 45-55 ft lbs I think. I can't think of any other cause unless the casting was defective and after 50 yrs maybe this is it.

Phil F

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Dennis

11-12-2002 15:43:15

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Re: Re: hydraulics with no pressure in reply to phil fenner, 11-11-2002 20:55:27

Phil,

If you need any parts for that pump, let me know. I still have the entire rear portion of a TO 30 pretty much intact!

Dennis

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rod

11-05-2002 13:43:28

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Re: hydraulics with no pressure in reply to phil fenner, 11-04-2002 16:01:34

you could have blown a gasket that is the gasket that is between the lift cylinder and the top cover there could be other problems you could try reaching in and moving the control fork by hand just to see what happens.
regards
rod

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phil fenner

11-05-2002 14:20:04

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Re: Re: hydraulics with no pressure in reply to rod, 11-05-2002 13:43:28

Rod, there are no gaskets in the TO-30 as "O" rings used, but anyway no oil showing up anywhere. I have moved the control fork many times and seems to be normal, but still no pressure when it is the "presure"position. When the lift was in an up position it held that position but would not go any further up so no leakage in that situation. Thanks, any more thoughts?

Phil

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James, UK

11-05-2002 03:20:17

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Re: hydraulics with no pressure in reply to phil fenner, 11-04-2002 16:01:34

I guess there will be others with more hydraulic experience than me who can provide better ideas, but having looked at how the system works:-

If the relief valve is not operating, then it's a good sign that it hasn't reached 2000 odd psi, yet. If the pump itself is not making very unhappy "I've got broken bits inside" noises, then assume that it is working OK, and the oil it is pumping is going somewhere.

Maybe the control valve on the end of the operating fork has either come disconnected (so fork isn't operating the valve properly) or maybe the valve is stuck in the 'down' position - in which case all the oil from the pump is being diverted back into the trans case at 'low' pressure.

You did say that you'd overhauled the whole thing recently - if this was the first time since that overhaul that you'd used it in anger, then it may just be a case of something not being connected right and jumping off. Here's hoping.

I can't believe that if it lifted the log OK you have damaged the pump - it'll be something really simple like the linkage.

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[email protected]

11-05-2002 14:28:55

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Re: Re: hydraulics with no pressure in reply to James, UK, 11-05-2002 03:20:17

James, I have been using it about a yr and have lifted other logs but not as heavy. The control fork and valve seem to be operating correctly as far as movement goes, so I am at a real loss to explain this result as the pump is going about its business quietly and correctly as far as I can see. But I see no evidence of oil being pumped anywhere. Could the side chamber valves get stuck somehow or the casting crack?? I checked the control valve connection with the fork and it is sound so the movement is about right(about an inch of throw in the valve)

Phil

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James, UK

11-06-2002 01:21:54

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Re: Re: Re: hydraulics with no pressure in reply to [email protected], 11-05-2002 14:28:55

Phil,

Back again and have just read all comments. What would the result be if either one (or both) of the chamber valves' springs broke? Being coil springs, they would collapse into themselves, so the valves would work (but only just) - which might explain why your lift arms will hold position, but not do anything useful.

I don't have a diagram to hand, so I can't figure it out for sure, and I'm not really sure what those valves do (I've never taken my pump apart, either) - but it may be worth a thought as your problem is a 'soft' failure rather than the usual 'BANG' which is usually easier to find.

Where would the oil go, and at what pressure (if any) if either or both of those springs was less springy?

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phil fenner

11-06-2002 10:52:55

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Re: Re: Re: Re: hydraulics with no pressure in reply to James, UK, 11-06-2002 01:21:54

James, thanks for your comments and ideas. I have taken my pump apart and could put it together blindfolded I think, but I am not sure how the oil moves through the passages of the pump casting either but the valve chambers must route the oil depending on the control valve position. But I would like to see an explanation and the overhaul manual doesn't do it. Never had to think about either til now. I may just have to breakdown and drop the pump and have a look, but it is disagreeable job.

Phil

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Jim W

11-05-2002 18:01:33

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Re: Re: Re: hydraulics with no pressure in reply to [email protected], 11-05-2002 14:28:55

I think you should normally see some amount of activity in the pump cavity, although not much. If everything is absolutely still you'd almost wonder if the pump is drawing fluid, so maybe one of the valves in a side chamber is acting up.
I hae also heard of the side chambers cracking but usually due to freezing, and with only a year since your rebuild there probably isn't much water in there.
I would just keep staring at the diagramme until something pops into your head.

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phil fenner

11-05-2002 21:03:36

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Re: Re: Re: Re: hydraulics with no pressure in reply to Jim W, 11-05-2002 18:01:33

Jim, thanks for the picture of the pump. I have it also and have been staring at it. There is oil movement around the pump to indicate the pump pistons are working, but no abnormal oil movements. I am sure nothing froze to cause damage as it hasn't been cold enough around here and tractor is garaged so no water entering the cavity anyway. It is a mystery.

Phil F

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Jim W

11-06-2002 06:43:21

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Re: Re: Re: Re: Re: hydraulics with no pressure in reply to phil fenner, 11-05-2002 21:03:36

How about the gasket between the top cover and the cylinder?
Jim
PS Does the lever on the quadrant feel normal i.e. as if you are moving the linkage inside properly?

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phil fenner

11-06-2002 10:57:20

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Re: Re: Re: Re: Re: Re: hydraulics with no pressure in reply to Jim W, 11-06-2002 06:43:21

Thanks for your suggestion, Jim but my TO30 has no gaskets in the top cover as "O" rings are used and I have inspected the area for leaks and find none! The quandrant lever feels good and I can see how it is moving the fork assy and control valve as I have the inspection plates removed and everything looks good, feels good, etc. I have moved the fork/control valve assy by hand and it seems normal to me. Next? Thanks.

Phil F

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Jim W

11-05-2002 18:08:09

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Re: Re: Re: Re: hydraulics with no pressure in reply to Jim W, 11-05-2002 18:01:33

Why can't I get these pictures to show up? Do they have to be jpgs?

Pump

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So now they show up! ?? Oh well

11-05-2002 18:12:12

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Re: Re: Re: Re: Re: hydraulics with no pressure in reply to Jim W, 11-05-2002 18:08:09

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