Hydraulic oil blowing out the vent

biggerred · Mar 6, 2015

I've got a smta with live hydraulics running a 3pt hitch, one remote, and a PS unit. My lift started slowing down so I used that as an excuse to get rid of the M&W pump (which was worn out!) and put a IH pump back on it. Before and after the pump change, I got/get sporadic oil blow out of the vent. (Unit under the gas tank) It has an old webster flow devider and an external pressure relief valve. Could the pressure relief valve be opening up and pumping straight to the tank?

David G · Mar 6, 2015

I would think it might, can you run it a little lower?

biggerred · Mar 6, 2015

It has a pressure relief valve like this one.

D Slater · Mar 6, 2015

Going to do some guessing. Does the line exiting the lower port of the priority valve go to the inlet of the control valve mounted by the seat? Does the return line from the control valve go to the reservoir port where the original pressure line from pump went? Does the pop off return line from the pressure relief valve and the priority safety valve go to the original reservoir pressure ports on the left side? If yes to those, may be air in system, reservoir to full or I suspect the steering motor return going in where the original operating lever and shaft was in the reservoir is to high up and above the fluid at least part of the time and causing a problem. See reservoir has the changeover breather installed. If it still has a pipe inside going over to near center of the reservoir the steering return is going to be pointed near its opening.
All of this depends if this is the tractor you pictured earlier and if I guessed correct on the plumbing.

biggerred · Mar 6, 2015

Dang Mr. Slater, your good! How'd you remember all those old pictures? Yep same tractor. I'll post a prepaint job picture. I changed a bunch of stuff on that tractor but the plumbing is still the same. (Except for the pump) I've checked the level and it's below the fill port.

David G · Mar 6, 2015

I meant level in tank

biggerred · Mar 6, 2015

Don't know what the change over breather is, but your explanation makes perfect sense.

biggerred · Mar 6, 2015

I've checked to be sure the level was below the fill port. I thought it was too full myself but apparently that's not the case.

D Slater · Mar 6, 2015

Breather with the round cap on the left side of the reservoir. Original breather was through the fill cap. One installed in your reservoir is a change. if complete it has around a 1/4 inch tube in the fitting going through reservoir wall. Tube extends over to near center way of the reservoir.
Looks like your reservoir has all the original valve and related parts removed and is just used only for a reservoir.

Janicholson · Mar 6, 2015

If everything you use is a double acting device, giving back as much as it gets, a vent system can be very limited. (possibly an extension to raise it higher, or a baffle to limit flowing fluid from splashing on it. Just food for thought. Jim

biggerred · Mar 6, 2015

Correct. Apparently it's been gutted. On the other side is a fill fitting (1/2 street el and plug) and a 1/4 tube with a vent cap like you'd find on a 300 or 400 reservoir.

biggerred · Mar 6, 2015

Here is one from my other smta. Where this one has a raised spot toward the rear, the one in question has a vent tube coming from that spot.

biggerred · Mar 6, 2015

Maybe i could do away with the external add on vent , plug it and go back with a vented cap?

mkirsch · Mar 6, 2015

It's below the fill port... WHEN, though?

It takes more oil to fill the extended cylinders than the retracted cylinders on that 3pt hitch. If you raise the hitch all the way up, extending the cylinders, then fill the reservoir, you will get oil blow-out from the vent when you lower the 3pt at all. Even a little bit. More oil will be coming in than going out.

This counts for any tractor: Check hydraulic oil levels with any attached cylinders completely retracted. That ensures the maximum amount of oil will be returned to the tractor.

biggerred · Mar 6, 2015

I double checked and I'm off a little on the vent location . It's not in that little spot but higher and toward the center.

biggerred · Mar 6, 2015

I've checked the level with the cylinders down.
It's below the fill tube.

D Slater · Mar 7, 2015

This is what your vent should look like. Its a better option than the original breather cap, unless you put another small tank in the fill opening. I would try teeing the return line from steering and control valve together. Or if it won't be in the way put return from steering into the right side former pressure outlet at rear of reservoir. Then plug the present return from steering in reservoir hole and give it a try.
Vent in picture should have a drilled and tapped hole near to top as possible on the left side of the reservoir and I think that's how yours is.

biggerred · Mar 7, 2015

Yes sir that be the culprit. It was straight across from the PS discharge line as you mentioned. I plugged that hole and put this (pictured) on the oil tank. When you mentioned the discharge line being directly opposite that vent tube , the bells started ringing and the light's started flashing, and I couldn't wait to get to the barn this morning to check it out. After running the tractor today it looks like that should work just fine. Thanks a ton Mr. D and everyone else! !

biggerred · Mar 7, 2015

Here's how it was

Hydraulic oil blowing out the vent

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