961 hydraulic question

Looking at a 961 that the current owner tells me has a hydraulic pump seal leak. Says he's getting hydraulic fluid in motor crankcase oil. Haven't had a chance to pull out the manuals yet but is there a seal that could be bad in just the actual pump itself or am I looking at a possible split to change seals? Just trying to find out what I'm getting into. Also noticed in pics the oil pressure at about 22# at 1100 rpm on the proof meter. Too low? Thanks!

It won't involve a split. If it is putting hydraulic fluid in the crankcase, it will be a problem in the pump.

22 psi at 1100 rpm could be just fine if the hydraulic system is not doing any work at the time. The pump produces flow and when there is no obstruction to that flow there is little or no pressure. it is the obstrucition to the flow that causes pressure. When the 3 point lift is doing no work (no matter whether it is currently holding up an implement or not) the fluid simply flows from the sump through the pump and back to the sump again with little or no obstruction. It is when the system is told to do work, like lifting an implement, that the flow gets diverted to do that work, and that is when pressure builds. Chain the 3 point arms down and move the quadrant handle to try to lift the arms and see what the pressure builds to. The highest reading you get should be when the relief valve opens, which should be around 2000 psi plus or minus a couple hundred. If the pump itself is leaking it might not be able to build that much pressure.

And there is no route between the hydraulic sump in that tractor and the engine crankcase except through the pump. So a pump rebuild is the proper fix, unless something in the pump like the body or head is cracked internally, and then a pump replacement would be the fix.

A leaking pump shaft seal can allow hydraulic oil into the crankcase. Sometimes this can be repaired by replacing the pump shaft seal but not always. If the pump shaft is worn you will need a replacement pump.

Engine oil pressure of 22 psig at 1,100 RPM indicates a rather loose rotating assembly, assuming that the gauge is accurate. That said you will likkely get away with it for years.

What oil is in the crankcase?

Dean

I have never been convinced that hydraulic oil can get into the engine through the hydraulic pump! One would surely be looking for major pumping problems before that would happen.
Engine oil pressure that low on that engine at idle is on the low side.

Hummm. I guess I might learn something with this.

I did not realize the hydraulic pump was open to the
crankcase. I thought it was like a starter and opened
to the flywheel and a leaky pump would put oil in the
clutch compartment

(quoted from post at 10:55:16 06/05/20) Hummm. I guess I might learn something with this.

I did not realize the hydraulic pump was open to the
crankcase. I thought it was like a starter and opened
to the flywheel and a leaky pump would put oil in the
clutch compartment

Click to expand...

ear on camshaft, not flywheel

The pump drive gear is driven by a gear on the rear end of the camshaft. Both are lubricated by engine oil.

Dean

The hydraulic pump seal is on the intake "suction" side of the pump. Thus all the comments about air in the hydraulic system.

Bingo.

Shut the engine down and oil in the pump above the level of the shaft seal will drain to parts unknown similar to countless other applications.

Anyone know of vintage Ford situations where engine oil is migrating to the hydraulic sump?

Dean

There should be nothing in the way back to the reservoir. Yes,it probably can happen, mechanically, but as you have asked, has it truly ever happen?

(quoted from post at 20:47:59 06/05/20) There should be nothing in the way back to the reservoir. Yes,it probably can happen, mechanically, but as you have asked, has it truly ever happen?

Click to expand...

eeds to run up hill doesn't it?

Thanks for all the input guys! I see the seal is still available if that's all it is. I'll go take a look at the tractor next weekend but the owner is asking premium price for a fair condition tractor. All I can do is offer what I think it's worth after I hear it run and take it for a spin.

(quoted from post at 13:38:39 06/05/20) A leaking pump shaft seal can allow hydraulic oil into the crankcase. Sometimes this can be repaired by replacing the pump shaft seal but not always. If the pump shaft is worn you will need a replacement pump.

Engine oil pressure of 22 psig at 1,100 RPM indicates a rather loose rotating assembly, assuming that the gauge is accurate. That said you will likkely get away with it for years.

What oil is in the crankcase?

Dean

Click to expand...

He tells me he put 10W30 in the crankcase. I bought some Rotella 15W40 Diesel rated that I've used in all my tractors before. I'll change the oil with that and see if pressure increases. If the same pressure, I'll try a new gauge before I dig any further.