That looks like the A/C liquid line, and the other end should go to the condenser at the radiator. You need a springlock tool to remove it.
If you remove it, the A/C refrigerant should be recovered by an A/C shop and not released into the atmosphere. Then the A/C will have to be evacuated and recharged when put back together.
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'89 LX 5.0 - 5 speed. Original Owner
'94 E-150 4.9 Hi-Top Conversion Van
'06 Mustang V-6, 5 speed
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