I have a 2004 Toyota Sienna that has 115,000 miles on it and I was havng problems with the steering. When you first start it up in the morning it was like the power steering was not working. After it warmed up, it seemed to get better. I read somewhere the steering shaft below the floor pan has a knuckle (like a drive shaft) that corrodes and becomes hard to operate properly. The shaft to the steering mechanism is exposed to the elements. I heard a bulletin was issued on this by Toyota, but not a recall.

I took some PB Blaster and sprayed the mentioned parts and seems to have cured the hard steering, even on cold mornings. Works like a new one and would save you a lot of $$$$ at the dealer or garage. Any rust exibitor (WD-40, Liquid Wrench etc.) would work. I'm sure I will have to spray it again at some point, but for now it works perfectly. It's easy for your mechanic to access on a lift, but I just used wheel ramps which worked ok. Let me know if anyone else has had this problem and hope this will work for you.