I've got a 1999 suburban 1500 2WD, 5.7gas with 260K on the clock. It has the towing package and rear heat/AC. I've had a nagging low level coolant leak for a while. I finally traced it to a joint in the lines carrying coolant to the rear unit. It appears that the lines are joined into front and rear sections along the frame rail just about where the back of the passenger's front seat is. Is there a fix for the joint, i.e. new seal, or am I looking at replacing the lines?