Tightness on Cap on Side of Coolant Reservoir?

Oh god, how much more frankenbs can we reengineer what aint busted already.

In my day you had two caps. One in overflow tank that really does not matter until it does and the other is at the radiator. That one matters as long it's strong enough to make pressure.

 

Think it's called packing to much under a hood. Hood sloped down and not room for nothing. Why i like a long hood. But guess i suffer mpg.

 

Loose cap, can’t be right. It probably has a 15-20 lb cap. System may be designed to run at 15? Must be what they mean. The pressure is needed to raise the boiling point, and increase cooling capability. That’s a closed system, design. Made to surge into overflow, when hot and expanding, and siphon back when cooling down. With cap loose, it’s no longer a closed system.It may not siphon back from bottom tank.