Need to bypass Rear heater Core from hood, Need help figuring out which lines...

[Tintooth213]

Hello, trying to bypass my rear heater core from under the hood I traced two aluminum lines that lead from around the coolant reservoir down under the vehicle into the rear heater core. I just need some confirmation on which two lines I need to bypass. The hoses are rubber under the head then turn into aluminum It also looks like one of the hoses is A/C. I really just need to stop flow to rear heater core from hood, there is a corroded line under the vehicle; where I would have to replace the whole aluminum lining. 04 Trailblazer 4.2L

 

[aaserv]

This is what I had to do on my Envoy, not positive its the same on the TB but I would think so. The control valve for the rear heater is mounted on the firewall behind the coolant reservoir . I of the lines running next to the valve cover has a tee in it which feeds this valve. I took the tee out and just disconnected that line to the valve. I really think that maybe all you need to do but I also cut the line that turns 90 degs and runs to the rear htg. It runs next to the A/C line. The main thing is to make sure you have the water running properly to the hookups that go into the firewall...those are the front heater. The others run to the rear without going into the firewall so it should be easy to tell which is which. Its probably easier to see which is which if you pull the reservoir out as I couldnt see the valve at all without pulling it... There is also a vacuum line running to that valve. I just disconnected it and plugged the end of it with JB Weld..

 

[TollKeeper]

Feeding line is always slightly larger than the return line, by like 1/8 inch.