Hydraulic motor keeps pushing seal out.

[3Lfarms]

But in his initial post the OP said that the seal was tight in the bore. It doesn't look like a pressure seal. It looks more like a type that keeps unpressurized oil from leaking and dirt from entering. That type seal is normally used for a shaft running in a vented cavity. And would explain the lack of a circlip.

I’m not sure where you are getting that OP said it was tight in the bore. He merely said that he “pushed it back in with a pry bar”.
That indicates to me that it is not a tight, press fit as it should be.

And while it is not a pressure seal, the body of the seal should not move, no matter how much pressure is behind it. OP didn’t think the motor had a high pressure leak, but even if it does, the oil should push out between the rubber lip and shaft, not push the metal body of the seal out of the bore.

 

[rScotty]

I’m not sure where you are getting that OP said it was tight in the bore. He merely said that he “pushed it back in with a pry bar”.
That indicates to me that it is not a tight, press fit as it should be.

And while it is not a pressure seal, the body of the seal should not move, no matter how much pressure is behind it. OP didn’t think the motor had a high pressure leak, but even if it does, the oil should push out between the rubber lip and shaft, not push the metal body of the seal out of the bore.

I disagree with your description of how that type of seal works. .In my opinion that type of pressed-in seal without a retainer is fairly easily pushed out of the bore by pressure. It isn't desgined to hold much pressure. Also, the more the internal pressure builds, the tighter the rubber lip fits around the shaft.
rScotty

 

[4570Man]

I’m not sure where you are getting that OP said it was tight in the bore. He merely said that he “pushed it back in with a pry bar”.
That indicates to me that it is not a tight, press fit as it should be.

And while it is not a pressure seal, the body of the seal should not move, no matter how much pressure is behind it. OP didn’t think the motor had a high pressure leak, but even if it does, the oil should push out between the rubber lip and shaft, not push the metal body of the seal out of the bore.

The seal is tight enough you can’t push it by hand. I probably put it in by lightly hammering in a circle around the edge. I replaced the seal but it was a generic seal so the possibility exists it’s a couple thousands undersize. I think you’re under estimating how much force it would take to push oil around the center and not push the body out. I think it would take several hundred psi to push past the center. In either case I plan on ordering an seal kit for the whole motor. I think the back plate on the motor leaks a little too. I guess this thing has cut enough grass it earns the right to leak a little oil but I’d prefer it didn’t. I think the suction hoses for the pumps are another source of leaks. I’ll probably replace them with pressure rated hoses with JIC fittings.

 

[gator]

If you don't already have it HERE IS A LINK for the Grasshopper service manual for the wheel motors and hydraulic pumps, the 428D is listed in it. It also has a parts breakdown in it.

 

[guitarman]

Yeah last thing I see in schematic on that end is item #12 listed ad a dirt and water seal which means its design is to keep stuff out not in should be a tight press fit if it's a little loose use the lock tite for seals I have used it before on loose seals does a good job of locking them in place

 

[oldnslo]

4570
I would recommend using hose rated for vacuum on the pump inlet. These are available with JIC ends. Standard pressure hoses may not be vacuum rated and the inner liner or tube on these hoses can collapse under vacuum causing pump cavitation

For reference most axial piston pumps and motors with lip style seal are only rated for around 30 PSI

 

[RickB]

4570


For reference most axial piston pumps and motors with lip style seal are only rated for around 30 PSI

Can you cite a source for this info or provide a particular hydrostatic pump/motor combination that operates at a system pressure anywhere near that value?

 

[4570Man]

So if I get this fixed should I I update the thread or should I leave it hanging and try for 1000 post on a seal that won’t stay stuck?

 

[RickB]

Time you get it fixed we will be there.:drink::drink:

 

[4570Man]

Time you get it fixed we will be there.:drink::drink:

Well it’s admittedly not top priority since it’ll be 1.5-2 months until I need it. But we’re a ways from there at 40 post.