Hydrostat issue...with video

[sawdustdad]

Originally Posted by Billy-O

I've been reading some (if not all) of this thread and I've been wondering if you inspected your bearing cages? Either on the input or output shafts. If a cage failed, the bearing could possibly jam. Forgive me if I missed any mentioning of this before.

Originally Posted by Mike McKown

I've been thinking this but............

That means there are two problems.

Bearings all look good. No gritty feel, no radial play.

[ICOM 756]

For giggles, I would swap the piston blocks. If the output starts spinning then you know that block had issues. Issue shows up as pump not as motor maybe ? Though, the blocks are the same, its a stumper ..

We need James Johnson to get it on this.

[Cubcadet_107]

Originally Posted by ICOM 756

We need James Johnson to get it on this.

...




In all seriousness though, I would swap the piston blocks just to see what happens (assuming you don't have any other plans for that hydro pump). Would be an interesting test that's for sure.

[Ambush]

I would advise against swapping the blocks because you can't swap the valve plates too and they are now "wear mated". Wouldn't matter 99% of the time, but you don't want to experience that other 1%. Also, sometimes motor barrels have different length ports then corresponding pump barrels. Measure with a caliper or check part number.

Pump valve plates have two notches and motors have four and sometimes a tiny hole at the end of the notch too. These are for pressure relief at the end of the work stroke/rotation. On pumps the notches also determine rotation.

Take the cover and remove every valve and plug from it. With a light look in every journal for hidden plugs that are used to block cross drillings and take those out also. Inspect each interior plug carefully because sometimes they are actually orifices that MUST be put back where they came from. Make sure you have every plug out.

Run a wire through all the journals. Then use a can of brake clean and spray in every journal from all ends by sticking the tube in . Do this over a clean white paper towel to see if you find material they may have been an obstruction. Then do it again using an air nozzle. Look for journals that don't seem to go anywhere, as they may be plugged.

Or swap in another clean cover.

Sometimes when the problem is not obvious, it's a process of elimination.

I'd really like to see the hydro running, because it's a real curiosity now.

[Cubcadet_107]

You're probably right. Same reason you shouldn't take the individual pistons out and put them back in different spots.

The only thing I can think of being an issue is one of the springs that holds the block assemblies under tension breaking. But I think he already said that they were fine.

[Ambush]

^^^. Swapping in known good components is an excellent trouble shooting strategy.

[Cubcadet_107]

Indeed it is, If finding a known good pump block assembly I would swap it in and see if that helps.

I was watching the 2nd video of the pump disassembled and I may have spotted something important. I noticed that the splines on the pump block actually look pretty worn out. They look quite flattened off:

Screenshot 2021-02-18 at 14.24.33.jpg

Now I suppose that could be the normal shape, but I then went and looked in my PDF service manual and the splines in IH's image definitely have a lot more of a point to them.

Screenshot 2021-02-18 at 14.24.41.jpg

I'm beginning to think that although it holds on okay under hand pressure, the worn splines might not hold up so well under the pressure of the hydro. When I get home I'll snap a pic of the splines from the block assy's of my 107's old hydro to see what they look like.

[ol'George]

Are you SURE the valve plates are installed CORRECTLY ?

[sawdustdad]

Originally Posted by ol'George

Are you SURE the valve plates are installed CORRECTLY ?

Yes. Removed exactly as installed originally and double checked against the manual. At least as sure as I can be.

I'm confident that is not the problem because the hydro stopped working before I removed it. In other words, it was working for a year, then stopped. Or gradually degraded to the point of failure over that year. Of course, that year was probably only 10 hours of actual operation. The hydro was in unknown but apparently working condition when installed from a tractor I bought and scrapped.

All the discussion is interesting and appreciated.

I removed the charge pump relief valve (spring and valve poppet, no shims) forward and reverse relief valves and plugs at the bottom of the cover. Everything looks clean and clear, no dirt, debris of any kind.

I will pull some of my spares and compare the splines, I agree they look worn in the pump block, but they seem to securely engage the input shaft.

The challenge (or pain) is each time I remove the hydro and reinstall it I need to remove and replace the fluid in the rear end.

I've got a line on a 1210 Cub that I will pick up next week from which to scavenge a (hopefully) working hydro.

I'll do some more digging and report back.

Just watched the successful landing on Mars. Exciting!

[ol'George]

If you pull the rear end and sit it on the back cover,( on a wooden block) you can unbolt the hydro, and not have to drain the oil as the hydro is then sitting on top of the reservoir. Yes?
( you will have oil in the hydro as you know, but not much more than a Qt.