Twice in the last two months, I've started my truck and had no power steering and no power brakes. I have no leaking hoses and the fluid in the power steering resivoir is at max capacity. I had it towed to the dealer and they have had it for three days. They hooked guages up to the system to check for leak down, and they said there was no problem with pump. I think there is a valve sticking in the pump. There could be something in there making that valve stick. It seems to do this when the truck sits for three or four days without driving it. They said they can't do much until it does it again. GM tech support hasn't been able to help them either. Some assistance would be great, thanks for listening. Dustin

The only valve in the pump is the pressure regulator valve. If the pressure line is removed from the pump, the valve will come out by unscrewing the part that the line went into. The valve is spring loaded. If the valve is pushed in and out against the spring, I would think you could feel it if it has any tight spots. Perhaps taking the valve out and lightly sanding it with some emery cloth might help if it has a burr on it. It may hang up when cold because the pump housing contracts, making the valve a bit tighter. That may be why it only seems to happen when it is at ambient temp.