Thanks for your help. To be honest i didn't check the preformed metal tube for cracks or defects. I'll have to remove the cover again & double check the lid & pipe assy's. The factory breather assy is in it's factory stock position with the hose running down to the tank ( the breather is about 6" or so above the tank.
Hmmmmm! Only a few other things I can even think of now would be if somebody has tried to reshape the bend in the return pipe that the filter threads on to, and possibly fractured it at the weld where the pipe meets the tank cover. This would tend to spray returning oil toward the vent pipe nipple opening in the tank cover (if the fracture was in the right place). Could even be a defect originating to when the return pipe was welded to the tank cover before the truck was built.
Those pipes are probably of the rolled and welded type and as such do have a seam in them. Maybe the seam opened up a bit when the pipe was bent to shape by the original vendor to Komatsu.
Is the vent still configured to OEM arrangement where the vent cap itself is mounted to the right rear FOPS upright pillar with a short hose leading to the tank nipple?
If someone has moved the vent cap to a location placing it lower than the tank cover (but why) I would expect oil to be expelled like you are seeing even if no other defect was present.
Long shots indeed, but this is an unusual condition so it doesn't hurt to check some unusual things.
Changed the in tank filter- unit still spits out hydraulic oil from breather- any other suggestions?
Spoke with my hydraulic vendor about the flow restrictor in the mast- I was advised that they don't come into play unless there is a hose breakage- that under normal circumstances they don't effect flow. He called the flow valve in the hoist cylinder feed line a "hydraulic fuse".
I would replace the return filter,check if the breather is realy clean and take a look at the restrictor in the mast,check if isnt lowering too fast than normal.
"Oil level is actually low"
That plus a clogged filter might be why.
If the filter is clogged (return hose jumps), the oil is probably unseating the filter bypass relief valve.
The relieved oil might be shooting out of the bypass valve at an angle that directs it by chance to the vent elbow pipe in the tank cover.
With oil hitting that elbow while the tank is venting out, oil will be carried out too.
Oil level is actually low. I haven't checked the filter inside the tank yet, can't see how that would cause oil to come out the breather. All hydraulic lines appear ok- return line from control valve to tank does physically jump when the hoist cyl is lowered.
This question sounds stupid,but is the oil level correct?
Can you check if the dipstick is the correct for that model or mast?
Had similar issue three weeks ago in a JCB telehander gearbox.Some "clever"guy swaped the dipstick for a smaler one from another model and i only noticed when was filling it.
Also check the return lines and filter inside the tank.
Hope this helps a bit.
Best regards.
R.Feitor