# Simplicity 5212.5 Hydro Dump Valve / Bypass Valve Stuck



## cpyne

Hi Everyone,

I just got this Simplicity 5212.5 free off Craigslist and I'm trying to sort out an issue with the hydro. Currently it will not disengage and the tires just skid if I try to roll it with the engine off. The transmission engagement lever moves, but the dump valve plunger does not move at all.

Should this be easy to push in and out? I've tapped it with a hammer and it does not move. I don't want to hit it too hard though since it may break something. 

Any advice on how to fix this? Does this indicate something fixable or a dead hydro?

thanks
Charlie


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## Hoodoo Valley

welcome to the forum Charlie! I'm not really sure on that particular set up, but someone here will chime in soon enough. Nice find though!


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## Guest

I'd pull the valve out and clean it to see if you can get it to move, its possibly stuck half in and half out... happens quite often with all the older hydros, sometimes you can save them or at least close them so the trans can work... there is someone is the US that rebuilds them but I dont have his contact info off hand...google 'hydrostatic relief valve' and Im sure you can find him. You might even be able to replace it with an auto valve like some Cub Cadets and Jacobsen tractors use.

just found this guy on fleabay.....
https://www.ebay.com/itm/REBUILD-SE...John-Deere-AM32939-Relief-Valve-/320670405175


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## cpyne

I was able to loosen the larger nut that is around the plunger. It slides off around the shaft of the plunger. The plunger then will move a little, but it is still stuck. I can put a wrench on the nut that is on the tip of the plunger, but it does not want to turn and it feels like I might break something. 

I did find this diagram for a Wheel Horse since it looks like they used the same transmission, "Eaton Model 7"

https://www.scribd.com/doc/50699099/WheelHorse-Eaton-model-7-service-manual


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## Guest

Dont turn the end of the plunger... they do break easily. Turning the outer nut didnt allow you pull the whole valve out??? I have an Allis Chalmers here which is built by Simplicity but it sounds like your valves are differant.... these ones dont have a nut on them... the valve body is machined for a wrench but the whole thing comes out in one piece.


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## cpyne

When I took off the nut around the plunger, it would move in and out a few mm, but it still seemed stuck. It would not twist at all though when I lightly tried it with a small wrench

The pdf I posted above shows it on pages 15 & 20


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## Guest

The valves on p20 look similar to the ones on my Deutz Allis mowers... maybe I'll have a look at those tomorrow


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## RC Wells

You are on the right track. What you have is the dump valve that is likely stuck, and the shaft with the hex head is the dump valve shaft. It is threaded into the dump valve bracket at around 12 to 24 inch pounds of torque. 

I would imagine the dump valve bracket itself is stuck in the depressed position. I would try to pull the shaft with just a moderate amount of force, and see if you can get the bracket to release. If it does not, you are going to have to disassemble the pintle and pull it out and determine why the dump valve bracket is stuck.

What happens is some operators forget to clean the housing of debris, and they overheat and shed metal fragments into the valves. 

These are among the best of the hydro transmissions ever made, and once repaired it should last pretty much forever if it is kept serviced. The unit you are looking at is the pump end, and is a current model with parts available directly from Eaton, or through places like this: https://hydrostaticparts.org/html/eaton_parts__hydrostatic_parts.html.

If it was overheated or run with the wrong hydraulic fluid, it may be advisable to just have an Eaton shop rebuild it for you.


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## cpyne

Great, Thanks for the info. I will let everyone know how I make out


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## cpyne

Thanks for the advice here. I'm still working on it, but I'm pretty sure that the Dump Valve Shaft is rusted/frozen to the Dump Valve Guide. After loosening the nut that is around the shaft, I can see that the shaft and stub of the guide that protrudes out will both spring in and out a bit when pushed, but the shaft does not move though the guide at all. I've got it soaking in PB which hopefully will free things up eventually


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## RC Wells

Bit by that elusive rust! The rust will eventually loosen with enough patience.

You want a penetrating oil better than PB Blaster and on par with Kroil, mix 50% ATF and 50% acetone. If you have a bit of pure Wintergreen oil, add a couple drops to the mix too, makes it penetrate even better.


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## cpyne

I got it free! The trick was to loosen the nut in the pic above and use lots of Kranoil and let it soak. Also things were made much easier by taking off the mower deck and the engagement lever. After a day of soaking, I put the nut back on tight and used my impact screw gun with a ratchet to dislodge the dump valve shaft. I did this gently, with just two impacts in the loose direction and then two in the tight direction, repeat, repeat, repeat. Gradually it loosened up. 

For anyone with a tractor like this, go put some lube on this thing. You don't want it rusting!


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## Guest

So what condition is the shaft in? bad I would expect


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## cpyne

Its actually in great shape. Repeated pressing of the plunger while spraying with PB and Kroil washed away the rust. It looks good as new


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