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Gordan

Can't find hydro relief valve on 918H

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Gordan

1692144 is the model number. All the manuals I've seen show a little elbow just in front of the rear axle, but mine has nothing of the sort. Looking at the parts manual, it looks like the hex cap bolt right under the free wheeling latch covers what's described as some type of relief valve. Is that what I need to open up when filling up the transmission?

When I remove the fill cap from the fill tube, fluid spills out. In one of my previous queries I was told that this shouldn't be able to happen... I'm nearly done with my propane Vanguard transplant but I want to make sure that other things are ok before firing her up.

Thanks in advance, as always!

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Gordan

Well, I looked both outside and between the side plates for something that looks like that, and found nothing. I guess I'll look harder.

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PhanDad

And here's a picture of it:

IMG_4787a.jpg

Although Simplicity calls it a relief valve, to me is a vent valve; basically a hole with a common nail in it which has a sloppy fit (and probably a flattened end inside so that you can't pull it all the way out. The actual hydraulic relief valves are under the freewheel latch as you stated; you don't usually mess with them. Also, when you check the fluid level, make sure you've run the engine recently. Mine bleeds down slow when not running and if you check the fluid level after it's been sitting, the fluid will overflow the fill pipe.

IMG_4787a.jpg.b5565ce04901dd0c4bcba4816de11068.jpg

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RayS

muf.jpg

I have this type on one or two of my tractors now. The other will get switched over as well as soon I do the next oil change. Available at most auto parts store.

muf.jpg.92f74a26c791535796c3f8dcc01fc0d1.jpg

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BLT
quote:Originally posted by Gordan

Well... I don't have it. Not at that location and not anywhere else. Now what do I do?


id="quote">
id="quote"> Take off the LH wheel and check to see if you have a square or socket head pie plug in the location where PhanDad indicated. Then go to hardware store and purchase a 1/4" X 2" NPT TBE nipple , and 90 degree NPT elbow and the appropriate 3/8 drive socket to remove pipe plug. When nipple and are installed with elbow facing down. You can now run it and not hurt anything for a bit until you get a valve to install.

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Gordan

Thanks for all the info, guys! I still feel like I might be missing the big picture - is what follows how it works? The hydro fluid lubricates the transmission and acts as the working fluid for the hydro pump/motor. The transmission case is like a sump/reservoir for the hydro and there's a pickup somewhere that goes to the filter, and a return back to the case. The transmission case should never be pressurized so it doesn't need a relief valve, and the only purpose for this little thingy stuck on top of the elbow is to provide a place for air to escape as you're adding fluid to the case. That pretty much it? Or does it have some type of function during normal operation?

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rokon2813

Also, as oil works it gets warm and as it warms it expands, need a place for air to escape then too. As it cools, it contracts, so air would be sucked back in too.

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Burntime

On my tractor I was washing it after a hard workout to find that the poppet was gone! I ended up just replacing it and changing the hydro oil and filter. I agree with the above, the oil needs to have a breather. Its simple plumbing if you don't have one. A quick fix...

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Gordan

Thanks again! Ok, not worried about the plumbing part - I redid the heating system in my house last year, some of the skills must've stuck. 8D Mostly I wasn't sure what the desired functionality was, but that's fixed now thanks to you guys. Something tells me that, once I remove the wheel to have a look at what I've got in that outlet, I will have found the source of the hydro fluid leak that I was wondering about in a previous thread...

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Gordan

...aaaand that's exactly what I found. Thankfully, I had a twelve-point star bit that I was able to tap in with a hammer and use to back the broken off piece of nipple out.

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