AC Low side suction line

It is best if you can add it onto the high side line, remember not to put in too much. If the system has no oil leaking from it do not put more than one once in it.

You are overlooking one critical point. You have a leaking valve in one of the charging ports. They all leak. The purpose of those valves is to hold the refrigerant in long enough to give you time to screw on the caps. The seal is inside the cap.

I would not worry about the dye. If you pump the system into a vacuum from both ports, you are likely to suck the dye back out. Same with the oil. One ounce, as Ken mentioned, is the standard amount for a new hose or steel line. Pour that right into the line as you install it, then just evacuate and charge the system like normal. If you desperately want dye in the system, consider pouring it into the new line, and forcing it to run away from the charging port before you make the final connection. If you can get it far enough away from the ports, there will be less chance of it getting sucked out.

Good to hear, please use 2CarPros anytime we are here to help.

Cheers, Ken