Just did this works great cold cold cold👍

 

I did a little changing around! It seems that the use of two shut off valves may stop heat into the heater core from convection via the return line. I used 3/4" shutoff valves with 5/8" nipples. I probably could have used the 1/2" shutoff valves but did not want to go smaller than 5/8" hoses.


(The 3/4" shutoff valve is much easier to turn than screwing the other shutoff valve.)

 

I know this is an old thread but....
Won't closing off the heater core inlet hose cause the water pump to eventually fail because of the built-up coolant/water pressure not being able to circulate?
If so, wouldnt it be prudent to insert a T- or Y-shape bypass-like valve instead of a complete cut-off valve?