coolant tank cap with relief valve

[Kevin ACR]

The cap on the coolant tank on the passenger side has been changed, it now has a pressure relief lever. Is this to allow air to be bled from the system? Would this simple change have a benefit by allowing us to bleed off air from the remote radiator tank?

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[Tom F&L GoR]

Not really. It's so you can relieve the pressure before you remove the cap, otherwise the potential hot spray of coolant gets all over you. I have this type and found that a) if the engine is hot and b) you lift the lever, you c) relieve the pressure, which d) allows boiling in the engine block. Remember, the 15 pounds pressure on the system is what helps raise the boiling point up to the 260F or so. Removing the pressure lowers the boiling point. And the air in the system that causes cooling problems isn't at the remote radiator tank, it's all those other spots in the system.