Oil Leaking from HST Filler/breather

[BruceV43]

I have a TYM 273 with mid mounted mower (TYM). Tractor has done 700 hrs and bought 3 mths ago s/h.

The more I use it the more it leaks HST oil from the filler/breather at the top of the transmission. I am planning to service the transmission shortly but reluctant until I understand why it is 'leaking' so much oil - any ideas anybody?

 

[BruceV43]

I have a TYM 273 with mid mounted mower (TYM). Tractor has done 700 hrs and bought 3 mths ago s/h.

The more I use it the more it leaks HST oil from the filler/breather at the top of the transmission. I am planning to service the transmission shortly but reluctant until I understand why it is 'leaking' so much oil - any ideas anybody?

Additional info:
I have confirmed that the oil is emerging directly from the filler plug which has a small hole, presumably to prevent any build of pressure although there is a separate vent pipe for this, which appears to leak very slightly.

The leakage amounts to about 1 litre for every 2-3 working hrs, which is a massive amount by any standards. In other respects the tractor runs well and all hydraulic systems are apparently normal - surely somebody must have some ideas??

One further point: I have run the tractor with the filler plug removed to see what happens. It's all ok when idling, ie low revs, but on increasing the revs, there is a fast flow across the filler opening (from rear to front), this ceases as soon as the auxiliary spool control (sticking out from below the driver's seat) is moved left or right to raise or lower the mower; normally it would be in the central position to neither raise or lower, ie a sort of neutral position. Is the leakage simply as a result of this 'churning' of fluid directly onto the base of the plug - if so, how can it be stopped?

Very puzzled TYM owner :confused2: