TYM 273 HYDRAULIC OVERFLOW

[Stumpshot]

My 273 with FEl and BH that blows Hyd fluid from the vent hose. The fill cap located on top of the selector valve for the hoe has a vent hole and there is also a vent tube coming out of the case. When I noticed the problem I plugged the hole in the cap thinking it didn't need 2 vents and that the bend in the vent hose would stop vapor from pushing the fluid out of the case. Nope. Now the vent line is spewing fluid when the machine is moving or working the loader or hoe. I'm new to tractors and I've only got 50 hours on this one. The dealer is 5 hours, one way, from me but we've talked about this and the only advice he had was to switch the backhoe hoses, which I did, but nothing changed.
Before I drive 10 hours does anyone have any sugestions?
This unit is an HST. I've made sure the PTO selector is in the off position just in case that was it and I've checked the HST fluid to make sure it was not over full. The selector valve (located under the seat) appears to have 2 positions. In one the the FEL operates and in the other the FEL and BH operate.
I'm running out of barnyard fixes. Anybody got ideas?
Thanks, Stumpshot.

 

[SHIFTY]

Does the backhoe move smoothly?
The valve below the seat in front controls the rear hydraulic valve.
If the backhoe is not moving freely, check the pin or ball on the coupler to be sure it releases fluid, Do this with the tractor off and the backhoe boom on the ground, Put a rag over the end and gently tap the pin or ball on the coupler (Be carfull if it is stuck -
It is under pressure).
Since this a new machine, Could it be overfull ? There should be a sight plug or dip stick. Good luck

 

[Stumpshot]

Shifty-
The backhoe runs just fine. There's a sight gage on the rear of the rig. I've got the fluid at a level between high and low. I'll try your sugestion on the ball and see if that changes anything.
Thanks for your help
Stump