DIY heater core bypass pipe size | Ford Explorer - Ford Ranger Forums - Serious Explorations

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DIY heater core bypass pipe size


Well-Known Member
August 2, 2009
Reaction score
City, State
Memphis, TN
Year, Model & Trim Level
2003 Mountaineer V8 4.6L
I'm getting ready to make a heater core bypass for a 2003 Mounty 4.6 V8 to troubleshoot a possible pinhole leak in the front heater core. I'm going to try and use a 2-head shower diverter so that I can shut off the flow of coolant going through the core, which would let it continue to circulate, or with a quarter turn, put it back in the loop. My question for anyone who may have already made a bypass is what size pipe or fittings did you use? I'm assuming the diverter valve will be 1/2" NPT thread, so I'd look for a screw on copper fitting to pipe, etc. Any recommendations?