What's The Deal With Heater Core

[jdlc]

When flushing coolant, Haynes and other write-ups, (true for other, different vehicles too) instruct turning up the heat to the max, suggesting the coolant would only cycle thru the heater core in such condition. Is this the case? Because I don't see any control that would stop thecoolant from flowing thru the core in my car.

The question is, when not turn on to heat, is coolant flowing thru the heater core? I think I know the answer, but how is this 'switching on/off' accomplished?

[Chilled man]

There isnt any stop valves in the heater core .

So not really sure.

I would say it runs coolant there every time the car is on.

Only time you get heat is when the dampers open up on it to push the heat through

[jdlc]

There isnt any stop valves in the heater core .

So not really sure.

I would say it runs coolant there every time the car is on.

Only time you get heat is when the dampers open up on it to push the heat through

Doesn't make sense why we need to turn up the heat when flushing, does it?

[Matty Moo]

My thinking.

Some cars have heater valves. I had a Cherokee that did. Usually a vacuum operated valve in one of the heater hoses before it hits the firewall. To get the hot water to flow to the heater core, the valve has to open. Turn your heat on high, and the valve opens, otherwise it bypasses the core. One more vacuum line and a $50 part to play with.

Every manual for just about every vehicle I've owned has said to turn the heat on high when burping or flushing. But, I've only had 1 car with an actual heater valve where it would make an actual difference.

So, I dunno.