Hustler super z hyperdrive hydraulic oil leaking from fill cap

[Alto1]

My hustler super z hyperdrive is leaking hydraulic oil from fill cap.
I didn’t overfill it.
Parked it in November after last mow and all was well.
Noticed today there is a substantial puddle of oil by mower and it looks like it came from hydraulic reservoir fill cap.
Parked it in a corner of pole barn and haven’t paid any attention to it till today when I noticed the leak.
Curious as to why that would be happening?
Anyone experience this problem or know what the issue could be?
Thanks!

 

[ILENGINE]

Possibly water getting into the oil tank and forcing the oil out.

 

[Alto1]

Possibly water getting into the oil tank and forcing the oil out.

It doesn’t get wet and stays inside when not in use.
I don’t wash it, just blow it off after each use. Residential use only.
Thanks for reply!

 

[StarTech]

First post the model number of the mower that way we can look up your setup.

Second looking and doing are two different things. For suspect oil leaks I use UV dye for tracing where the actual leak source is.

 

[Alto1]

First post the model number of the mower that way we can look up your setup.

Second looking and doing are two different things. For suspect oil leaks I use UV dye for tracing where the actual leak source is.

Model number is 932160.
I don’t have uv dye.
Been around farm equipment all
my life and it is definitely from the top of the reservoir.
I haven’t replaced the cap since new.
I’m definitely going to do that and go from there.
Any other suggestions?

 

[StarTech]

When was that last time you change the filter?

 

[Alto1]

When was that last time you change the filter?

411 hours ago.