Hydraulics sudden burp?

[FarmerInTraining]

I recently refilled the hydraulic fluid for the tractor bucket, and two days after the fact it suddenly sprays (maybe a quart) out the top when under no particular strain that instant. Been using the bucket heavily for two days with no issue, so if the lid were loose I'd expect gradual leak not sudden spurt (lid is still intact).

Does anyone know what this might mean?

 

[5030]

Overfilled and thermal expansion forced it out...

 

[FarmerInTraining]

Overfilled and thermal expansion forced it out...

That makes sense. Thanks.