1990 Honda accord EX

What is the large pipe/hose that has a BIG hex nut 20mm or bigger, that is on top of radiator, right in the front of the car?

I need to unhook this to make room for my tool, what's in it?

It has a blue cap also attached to it, under the cap there is a pressure device connection? a female shrader valve?

Thanks.


*edit, I think it's the air conditioning evaporator hose? Is it okay to unplug this temporarily so I can get more space?

 

Pressurized refrigerant and compressor oil are in it. Unhooking it is bad, don't do it. Find some other way to get your tool in.

If you unhook that line all your refrigerant will escape into the atmosphere. Damaging the ozone layer, possibly freezing your hand solid, and you will have to get your air conditioning system recharged and re-oiled after you do it.