Hydraulic oil backing up

[daysailor]

When my 1976 IH-464 gets hot, the hydraulic oil starts coming up through the dipstick. Not much, just enough to make a mess. This just started happening recently. I have replaced the hydraulic oil filter, but it still happens. Any ideas what might be wrong?

Daysailor

 

[Zebrafive]

Not familar with this tractor, but my first thought is there is a vent that's plugged so dipstick has become the vent.

 

[Soundguy]

did you change oil type to a thicker oil?

did you overfill it?

 

[wdchyd]

Does your oil look foamy..??

if so, the air/foam will take up room in your hyd system and return oil will burp out the vent (similar to overfilling) when you retract cyls