Quote:
Originally Posted by rrgrassi
Try the cap first as indicated.
If there is a coolant leak, the hose should not collapse as air replaces the missing coolant.
If you remove the cap, does the hose expand back to normal?
The hose collapses because the pressure inside the cooling system is less than the atmospheric pressure. On a cold engine, the internal and atmospheric pressures should be about equal.
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In addition, if the cap is bad, it tends to let some coolant out (worn spring/seals). So when the car cools down, the cooling system has less coolant to go with, so a vacuum develops and the hoses collapse.