I was wondering if not having the coolant diverter valve in place was bad for the heater core. When I bought the car three years ago the heater was bypassed. When I installed the new heater core nine months later I did so without the valve as it was missing. Now about a year and a half later I have a bad heater core again (excessive coolant loss, coolant smell, wet passenger carpet and puddle under pass side of car, fogging windshield while driving). Did this cause a premature failure or did my aftermarket part just fail. Thanks.

 

The only thing that valve does is shut off water flow to the heater core when you turn the AC on. It makes the AC blow just a little colder. Lots of cars out there dont have that valve and have coolant flowing through the heater core at all times.

Sounds like your core just failed. What company made it?

 

the temperature selector is set all the way to cold.

 

I don't remember which company made it. The company I work for allows me to get factory parts at a discount so I will will just pick one up if they are still available.

 

Pillsbry (member here) just replaced his heater core in his xtreme (borrowing my garage), it (the old) was well less than a year old and it failed.

 

I was under the impression it shut off the flow when the AC was set to MAX AC, not the temp selector. I guess I learned something...

 

Max A/C opens a door to recirculate cabin air.
There is a little vac valve (on the hvac control) that opens when the temp is moved to cold. It passes vacuum to the diverter valve to reroute coolant away from the heater core.
I never knew (or cared, really) myself how it worked untill I had to change the hvac controls in my old '84 camaro with a unit from a newer 'bird.