Radiator hoses collapsed when cold and gurgle in heater core
I think you coolant level is low. I also suspect that your radiator cap is not allowing coolant to flow back into the engine from the reservoir when the engine cools off.
My upper hose is really soft too, I should add. Also, only one of my heater core hoses are hot, the other barely warm and I have no heat, especially while driving 55. I've replaced the thermostat three time in the last theee months, just in case. The car runs fine other that the air coming back into the heater core every few months. Pressure test checked out, nothing found in oil, as in milky sludge, negative on white smoke and negative on any carbons in the coolant. I'm at a loss. Would the weak hose be causing my issues, would the heater core cause these issues, should I drive it off if a bridge?
If you are not loosing coolant and your cap is releasing pressure build up correctly, you may have a water pump that is not functioning properly. First, check the serpentine belt for potential slippage. If it seems OK, remove it and try spinning the water pump by hand for smoothness and stiffness of operation. It may have internally destroyed itself and decreased coolant circulation.
Looking for a Used Grand Prix in your area?
CarGurus has 79 nationwide Grand Prix listings starting at $1,800.
Search Pontiac Grand Prix Questions
Pontiac Grand Prix Experts