Rear brake line help

Ditto. Replace all lines that are not new. Get a new T-fitting. Rubber and steel. Brake lines like coolant hoses go bad from the inside out.
Any crud that was in the lines will now be in your calipers and wheel cylinders . Always flush/replace lines BEFORE you connect to new calipers/wheel cylinders or you just contaminate evrything.
Alway use brand new brake fluid from a sealed bottle. Toss all brake fluid that is in a resealed container. Not worth it.
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