Did you contact Hoover? In my experience with a Hoover shampooer, they are great at resolving issues with their products. I still have my Hoover shampooer after 14 years. It has never been serviced but after using it for over 2 years, the original leaking, defective water tank was replaced fast and free of charge by Hoover.
My Hoover vaccum lasted for 9 years without ever being serviced. The only reason I got a new one is because after using it so long and having dogs, when I vacuumed I could smell dog hair. I now have a Shark Professional and love it.