I pour in fluid and it all ends up on the ground.I will obviously check for holes and cracks in the reservoir but are there any other common causes of this. My mechanic says that the seal sometimes wears out and causes this?

Thanks

 

Its a cheap plastic container, so I assume over time it will begin to break down and crack. My fluid holder on my old mustang used to leak bad, got another one from ANOTHER old mustang and it solved the problem! Good luck!

 

You took it to a mechanic? Just get under the hood and have someone fill it up while you watch. If you can replace it with one from a junkyard, I see them all the time.