I have an 01 ody and was changing my plugs. The middle one in the back is blocked by a hose. I tried to take it off and some greenish/bluish liquid started to come out, so I stopped and didn't take it off. So I couldn't change the plug. I want to know what it is before I take it off. Can anyone help? Will post pic when I get home. The hose is about an inch in diameter

 

definitely a coolant line it sounds like. In for pics

 

here is the hose

 

it is directly behind the middle plug on the back

 

coolant line.

 

Ok, so how can I change that back middle plug without undoing that hose and having coolant spilling everywhere

 

that hose = heater core hose

hope you didn't introduce air into the system; check your temp gauge and hope that you're not overheating.

if you can't access the plug, then move it out of the way & then re-attach & burp the air bubbles out of the cooling system

 

You do not need to remove the hose to change the plug, just work around it. Try a different length extension and/or ratchet to get the plug out.