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Heater Valve "bypass" leakage

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Has anyone done a pressure test of just the brass heater valve (air pressurize one end ~15 PSI with the other end underwater)? 


I've got several candidate valves for my car, all of which I disassembled and cleaned carefully (along with new o-rings), and all of which have a wee bit of leakage at the outlet, both before and after disassembly.  But nothing leaking out of the control stem, thank goodness!    I think it will be a small enough amount of water flow that it won't be noticed in practice.  I assume this isn't a "feature" of the valve design, and that if air leaks, so will water and antifreeze. 


Comments?  thanks.

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Keep in mind that the newer valves (think they started in 1974) have a small hole in the valve that will allow a minimal coolant flow through the heater core, even when the valve is fully closed.  The factory found out that if the core was completely shut off from coolant circulation (as it would be in the summer, or year round in warm climates)  it would clog up the heater core, so they added that small hole.  Check your valve for this hole; that may be the source of your leak.  If so, it's intentional.



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Yup, it's certainly a feature.  Oddly, it's for warmer climates, where the

heater core didn't get flow for up to years, and the additives would settle

out of the coolant, plugging and rotting things as Mike says.


I too pressurize a valve that I've rebuilt- takes very little time

compared to the fiasco that is heater box removal...



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