Coolant Flow for 4.6L modular engine
Note that: before the t-stat opens (engine cold), ALL of the water pump's pressure goes thru the heater core. So the high coolant flow at that time will self-bleed any air out of the heater core, but it can also overpressure the core, which is why Ford is now adding a restrictor to many vehicles. See the TSB in this caption:
Smallblock V8
![coolant-flow.jpg Coolant Flow for 4.6L modular engine
Note that: before the t-stat opens (engine cold), ALL of the water pump's pressure goes thru the heater core. So the high coolant flow at that time will self-bleed any air out of the heater core, but it can also overpressure the core, which is why Ford is now adding a restrictor to many vehicles. See the TSB in this caption:
[url=http://www.supermotors.net/registry/media/743849][img]http://www.supermotors.net/getfile/743849/thumbnail/heatercore.jpg[/img][/url]
Smallblock V8
[url=http://www.supermotors.net/registry/media/172860][img]http://www.supermotors.net/getfile/172860/thumbnail/smallblockcooling.jpg[/img][/url]](https://www.supermotors.net/getfile/167728/fullsize/coolant-flow.jpg)