I've had same issues with 2 and 3 Stage tk jacks. You do have to change all the packing seals, internal and external. There are check valves at the bottom of the lower plunger on a 2 stage and the lower and middle plunger on a 3 satge. TK says they haven't had issues with these since 2003 so it's more than likely the packings. I have instructions on the procedure so pm me an email address if you need it. You will need to hang the car and have a couple of good chain wrenches and a strap wrench to disassemble the heads. I've had to do this on a few that were less than 2 years old. Bad batch of packings or poor design???