[wnewport]

When my car is cold the upper radiator hose is collapsed. When I loosen the overflow tank cap it "inflates" again. Is this normal?

Thanks.

2001 DB7 Vantage Volante (US)

 

[Vulcan]

No, it should not be collapsed. When hot the pressure builds up in the cooling system and this lifts the spring on the expansion tank cap. The pressure exits via the small pipe by the cap. When it cools the pressure drops and a vacuum is formed which draws air back in - or coolant if there is an overflow bottle attached.
Check the overflow pipe for blockage from the tank to the outlet. It could also be a faulty tank cap or the top hose has lost its resistance and become weak. If the pipe is easily squashed and feels soft, I'd replace it.

 

[wnewport]

No, it should not be collapsed. When hot the pressure builds up in the cooling system and this lifts the spring on the expansion tank cap. The pressure exits via the small pipe by the cap. When it cools the pressure drops and a vacuum is formed which draws air back in - or coolant if there is an overflow bottle attached.
Check the overflow pipe for blockage from the tank to the outlet. It could also be a faulty tank cap or the top hose has lost its resistance and become weak. If the pipe is easily squashed and feels soft, I'd replace it.

I checked and it's not a plugged hose to the overflow tank or the hoses to the expansion tank.

How can I test the cap to make sure it lifts on vacuum? (I pressed on the brass disc to ensure it lifts on pressure.)