Changed hydro pump seals, no hydraulics now

greasemonkoid · #1 09-03-2017, 11:37 AM

I'm tickled to have found a neat forum dedicated to these cubs!

I hope there is an easy fix for this problem, I've become frustrated and need this machine to be running.

The machine is a 1782, was running fine until the seals in the pump and axles began to leak bad enough I decided it was time to tear it down.

I changed every seal in the pump, every component was carefully laid out and assembled in reverse order, the block and piston assemblies stayed together. I've done one of these Cub pumps in the past (seal wise) and didn't have any problems, but this thing is making me pull hair.

The filter is new, full of cub original petroleum hydrostatic fluid (2 gallons), and there is nothing functioning at all. I ran the thing probably 15 minutes by now - hope no bearings are damaged - cycled the speed and everything countless times. I even flipped the charge pump just for the heck of it. I pulled the relief valves to see if one was stuck open, but they appear fine and functional. It is worth noting that while the relief valves were out I spun the input shaft with a drill to see what would happen, it is definitely pumping fluid because it will quickly push fluid through the relief valve holes. Why there is no prerssure, I have no idea. There are some bubbles on the dipstick after a run and the entire pump does get slightly warm after running a bit.

Hope someone will have an idea I haven't thought of yet.

I've done a lot of searching on this site but still lost. Big thanks in advance!

greasemonkoid · #2 09-03-2017, 08:39 PM

After sacrificing a Sunday it is evident that the valve plate on the pump side - if that is correct terminology - had slipped upon reassembly, not much but about a locating pin width and I didn't know it. That was the problem. Unfortunately, there was some damage done. There is an ultra-fine glitter of ferrous shavings in the fluid, a magnet's lines of flux can be seen in it.

That plate/valve is apparently a bronze coated steel, it may have worn, but something else in there was wearing also, hence the ferrous glitter.

Does anyone know where to go for affordable rebuild parts. I see that valve alone runs about $250. A whole tractor can be bought for that price. It's surely time for a service manual.

ol'George · #3 09-03-2017, 09:07 PM

Used one on epay # 262920897451
or place a want ad here

J-Mech · #4 09-03-2017, 10:53 PM

I don't know how you would have bolted it together with the valve plate not on the locating pin. It should have gotten stupid tight before coming together.

Second, you can't run a pump not pumping for 15 minutes and not expect damage. Why don't you go drain the oil out of the motor in your car and run it for 15 min. Hydraulic pumps don't splash lube. They are pressure fed. If nothing is working, the worst thing you can do is keep running it.

The ONLY seal that requires disassembly of the pump to change is the left side trunion shaft seal, and they almost NEVER leak. You shouldn't have even taken it apart.

Well.... lesson learned. You ruined your own pump. Find a good used one.

greasemonkoid · #5 09-04-2017, 06:04 AM

Yeah, I deserved that one. That side seal was one that was leaking.

Interesting that everything bolted back together fine. Before running it was disconcerting knowing there wouldn't be pressure on the bearings, but they are ball, and should handle a bit of running without pressure lubrication. I failed to think of the metal on metal between the plate and the piston and block assembly as is a crank journal in an engine.

Thanks olGeorge, I'll probably grab that pump and a spare when another comes up.

I love my 1782, gotta keep her going.

J-Mech · #6 09-04-2017, 08:16 AM

Quote:

Originally Posted by greasemonkoid

Before running it was disconcerting knowing there wouldn't be pressure on the bearings, but they are ball, and should handle a bit of running without pressure lubrication.

There is only 1 ball bearing in a Sundstrand hydro. Needle roller bearings are used in every location except on the back of the input shaft.

You didn't hurt the bearings. They could run for hours with only the oil use for assembly. All the bearings are splash lubed, or submerged. The slipper pads, swash plate, and valve block, and charge pump are what are so critical. Without oil, they won't last long.

You say that the trunk on shaft on the linkage side of the pump was leaking? It's possible, but I'm skeptical that seal was leaking. It's always the right side that the seal fails on. Between the repairs I've done, and every leaking hydro thread on this site, I'd say it's close to 99% of the time failure of the right side seal. You sure it wasn't the relief valve leaking, and running down?

You need only buy one pump. A spare is not necessary. Failure rate on a hydro almost never. Basically things can cause them to fail: towing too fast or gross lack of maintenance over the coarse of 30 years (I mean GROSS negligence). Neither of those things are even really a hydro failure as they are operator induced.

greasemonkoid · #7 09-04-2017, 09:26 PM

A low failure rate is reassuring. I could be wrong, but the oil trail seemed to come from that side requiring disassembly, was hoping to eliminate tearing it back down if I took that chance, but yet I didn't know the statistics either. Another pump is on the way.

It is time to quit attempting repair work in haste - it never ends well. Lesson learned. Again... Life is chaotic at times.

A spare backup machine is in order at some point. You don't realize how important something is until you lose it.

Thankyou for the help sir.

ol'George · #8 09-04-2017, 09:32 PM

To put your mind @ ease, I'm one of the 1%ers that had that seal leak that required disassembly of a hydro,
so it does happen.

J-Mech · #9 09-04-2017, 09:43 PM

Quote:

Originally Posted by ol'George

To put your mind @ ease, I'm one of the 1%ers that had that seal leak that required disassembly of a hydro,
so it does happen.

Oh, I've changed them too..... but only a couple times. On my 1811, I've changed the right seal 2 or 3 times since I bought it in 2001. Never done the left side that I can recall.

I did two left side seals back to back one summer. One for a buddy, and I can't remember what the other one was on....

So, I agree, they can and will leak...... but it's almost always the right side.