This happened this week: a friend was driving the 2008 Pathfinder and the infamous heater pipe broke at the plastic fitting. So, we got the vehicle to my house and I gave her my 2006 Pathfinder to use. Guess what happened? A few days later, the same thing happened with the heater pipe on the 2006! I got the new heater pipe for $250 (Quirkparts via Amazon.com) and put it in on Friday. I was a little concerned about getting the end of the pipe that was broken inside the hose out, but it literally crumbled into pieces when I squeezed the hose (fortunately I was able to push the hose down before it fell into the cooling system). I was going to do a "how to" on it, but there are already a few good "how to" vids on YouTube such as this:
A couple of key points and tips: You need to remove the passenger-front wheel and the plastic wheel well liner; once you do, the bottom end of the pipe assembly is right there! You don't need to remove the upper intake plenum nor the cover over it; it's a tight squeeze to get out, but a little patience and pulling up on the harness on the firewall and it will slip out and in (I actually took my cordless sawzall and cut the pipe into three pieces for easier removal). I have a carburetor adjustment tool with a 1/4" drive end and a 45-degree bend at the end; combined with a 10mm socket, it made getting the two nuts off of the firewall a piece of cake! Perhaps the worst part of the job was getting to the spring clamps on the hoses at the heater core outlets and removing the hoses from it! As suggested in the video, lube the inside ends of the hoses with liquid dish detergent and they'll slide on the pipes with a slight push. I ended up needing two gallons of coolant, exactly, and I did drain the radiator first. $250 shipped and with taxes is the cheapest I could find the pipe for, which I found on Amazon and also NissanPartsDeal.com and a couple other places. Part of the reason why it's so costly is that it comes with a new heater pump, along with hoses and spring clamps. If you have a V6-powered, R51 Pathfinder with rear heat, the Nissan part # is 92408-ZL90B.
Both Pathfinders have over 200,000 miles on them (254,000 and 210,000, respectively) and are over 10-years old (12-years and 14-years, respectively). With that in mind and considering how brittle the plastic was, my recommendation to all is that if your Pathfinder is 10+ years old and has high mileage, you should really consider replacing this part as "preventative maintenance" rather than take a chance on it breaking on you when you're on the road. My 2006 broke in Virginia Beach, which is over 3-hours from my house and a $1000 tow bill! Fortunately, my friend had towing insurance which cut it down to $540...but still! So, don't say I didn't warn you!