heater control valve help!!!

[danczern90]

What's up guys? I have a 95 ford ranger 3.0 that keeps blowing out heater cores on me. It all started when I got the trans rebuilt, then flushed the coolant and changed the stat. First few months were fine, then it blew out again. Replaced it, then it blew out 3 weeks later. Now I'm on my third replacement and I have a feeling it is because someone deleted the control valve. I need to figure out where the vacuum for the heater control valve goes to so I can reconnect it. Any help would be much appreciated. Thanks.

 

[RonD]

My '94 4.0l doesn't have a heat control valve, heater core has coolant passing thru it all the time, it is the by-pass for the water pump, engine would over heat if a valve was installed.
I know this because heater core got partially clogged and the engine temp would randomly spike, then go back to normal.
Replaced core(after a few other parts that didn't help, lol) and all has been well.

Make sure you are running a 192deg or 195deg t-stat, and if 3rd core goes try a different brand.

How are they "blowing out"?
older cores can rust thru, new core blow out could just be bad soldering.

 

[martin]

Bad rad cap can cause excess pressure in the system.