Kubota L4310: Lots of high pressure air coming out of hydraulic filler cap

[fbitz777]

I was trying to top off the hydraulic but as soon as I let the filler cap off a lot of high pressure air (hot) comes out

This tractor was just serviced and I am assuming they put new hydraulic oil/filter since they had to split the tractor open to replace PTO clutch

Any lead appreciated!

 

[rScotty]

It's not unusual for that type of hydraulic system to get full of air after some work done and then purge itself of air. What is unusual is that the air should be going out the vent pipe. I wonder if that hyd vent pipe is plugged? Sometimes wasps will build mud nests in those pipes and plug them.

The vent is just a curved pipe - sometimes plastic tube on top of the hydrauic sump...often at a high point on the casting either above the rear axle or below the seat mount.
rScotty

 

[fbitz777]

It's not unusual for that type of hydraulic system to get full of air after some work done and then purge itself of air. What is unusual is that the air should be going out the vent pipe. I wonder if that hyd vent pipe is plugged? Sometimes wasps will build mud nests in those pipes and plug them.

The vent is just a curved pipe - sometimes plastic tube on top of the hydrauic sump...often at a high point on the casting either above the rear axle or below the seat mount.
rScotty

Found it!

 

[rScotty]

Found it!

I hope that means that it is venting properly now. You do not want positive pressure in the hydraulic sump. Yours and most tractors have an "open hydraulic system". One of those features is that the return system sump/tank/reservoir has a free air space above the fluid that is open to atmospheric pressure. All of the various shaft seals in and out of that sump are not designed to handle pressure from inside. They will handle some, and much better when warm than cold - so I wouldn't worry about mild pressure. But good to fix it.

If there is any doubt about venting or pressure in the hydraulic sump, drill a small - 1/16"hole is fine - in the filler cap. You can seal the hole with a screw or replace the cap when you are confident it is venting. Or you could become a "belt and suspender guy" and turn the hole into another vent.

rScotty

 

[Smokeydog]

Since the tractor was split check all exterior suction line connections. Air inleakage from rubber line connections happen. Also check hydraulic filters for tightness.

Good working vent important. After the system is bled the hydraulic oil should not be foamy or trying to blow out the fill port or vent.