There seems to be an intermittent chirping type sound coming from my PS pump (especially when cold, quiets after driving). I don't know if it is the bearing (~106K miles) or possibly air in the system. It started after the car sat for a few weeks, parked on a hill. At the same time the low coolant warning appeared for the first time ever since I've owned the vehicle. Checking the coolant reservior, it was very low. I feared the worst, (head gasket) but upon investigation found a pinhole in the plastic tank of the radiator (Relief!) on the same side as the PS pump. For something that protects against corrosion, coolant is very corrosive outside the engine. I am wondering if these two problems are related in some way. I've ordered a new radiator but am not sure about the PS pump yet.