The upper radiator collapses when the engine cools. What is the most likely cause? a. Defective upper radiator hose b. Missing spring from the upper radiator hose, which is used to keep it from...

The upper radiator collapses when the engine cools. What is the most likely cause?

a. Defective upper radiator hose b. Missing spring from the upper radiator hose, which is used to keep it from collapsing c. Defective thermostat d. Defective pressure cap