I've been having some steering difficulties with my Toro Z-150 and thought you might be able to help. I know, it's a Toro...but hey, Toro owns Exmark now right? The mower was purchased new in '99. Anyhow, the right steering arm will "lock-up" unpredictably while operating the machine causing a loss of steering which is somewhat disconcerting to say the least. It's happened while moving forward, and while moving in reverse, and while at top speed, or at slower speeds. If I'm on a wide open lawn I can bring the other (left) lever even with the right then 'toggle' the right to get it free. If I'm in a tight area, or a potentially dangerous area (i.e. slopeside, or roadside) I have to reach down and turn the key to kill the engine entirely. The service guy I use isn't a Toro or Exmark dealer. He's an independent shop owner. He figured it to be a pump problem and bled the pumps dry according to the manual, then refilled with Mobil 1. This didn't help. His brother works for a company called Parker which is a hydrolic pump manufacturer and he and an engineer from Parker disassembled the pump to have a look and could find nothing wrong. They all are puzzled, in that the problem is only on one side considering both pumps draw from the same resevoir. I'm wondering if it could be a steering linkage problem, rather than a pump problem. Do you have any suggestions for a problem of this nature? Thanks much.