Heater Inlet vs Outlet. Which is which?
Welcome to the forum
Heater core is just an s-shaped pipe with fins so no IN or OUT assigned or needed.
If you are back flushing the heater core so want to see which one is OUT, then start engine and turn heater on.
Feel both hoses at the firewall, the one that warms up first or is hotter is the IN, making the other one OUT
I often reverse the heater hoses each time I change coolant, like back flushing on the fly, lol.
Heater core is just an s-shaped pipe with fins so no IN or OUT assigned or needed.
If you are back flushing the heater core so want to see which one is OUT, then start engine and turn heater on.
Feel both hoses at the firewall, the one that warms up first or is hotter is the IN, making the other one OUT
I often reverse the heater hoses each time I change coolant, like back flushing on the fly, lol.
Last edited by RonD; Jun 18, 2016 at 02:47 PM.
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From: Beech Mountain, NC
Flow Direction
Dear Members,
I am new to the forum, glad to be here. My first post. I came to this post to determine the input and output of the heater core. I understand the core itself is not polarized as in and out, and is bidirectional. I my case the flow direction is important. Let me explain. I live on Beech Mountain in NC, and it gets extremely cold here, I am storing my new (to me) Ranger Edge 2002 V6 outside. I purchased an aftermarket German made coolant heater-thermostat-pump assembly for the truck to keep it warm overnight. The unit has a flow direction arrow indicated for the coolant. I installed the unit between the heater control valve and the engine as I thought that this was the inward flowing line to the heater core and put the arrow pointing into the heater core. I fired up the truck and no leaks or problems, the heater works great and the engine heats up normally and regulates as expected. After the Edge warmed up, I felt the hoses and to my dismay the hotter hose is not the one where I installed the unit. So I concluded that I have made an error. Does it really matter about the direction and the hotter hose?? What do you guys think?? Moving it is not too difficult, just more time and work in the winter cold. Bob
I am new to the forum, glad to be here. My first post. I came to this post to determine the input and output of the heater core. I understand the core itself is not polarized as in and out, and is bidirectional. I my case the flow direction is important. Let me explain. I live on Beech Mountain in NC, and it gets extremely cold here, I am storing my new (to me) Ranger Edge 2002 V6 outside. I purchased an aftermarket German made coolant heater-thermostat-pump assembly for the truck to keep it warm overnight. The unit has a flow direction arrow indicated for the coolant. I installed the unit between the heater control valve and the engine as I thought that this was the inward flowing line to the heater core and put the arrow pointing into the heater core. I fired up the truck and no leaks or problems, the heater works great and the engine heats up normally and regulates as expected. After the Edge warmed up, I felt the hoses and to my dismay the hotter hose is not the one where I installed the unit. So I concluded that I have made an error. Does it really matter about the direction and the hotter hose?? What do you guys think?? Moving it is not too difficult, just more time and work in the winter cold. Bob
Welcome to the forum
The warmer hose will be the outflow from the water pump to the heater core, after coolant flows thru the heater core it returns(cooler now) to the engine cooling system.
While the heater core itself has no direction, no IN or OUT, the flow thru the heater hoses does have an out and in.
While the added pump will circulate coolant when engine is off regardless of which hose it is on, I would still move it to reflect correct coolant flow direction, from the engine.
OR.......you can just reverse its direction on the hose it is on now.
As said above hoses on the heater core don't matter, they can, and I might add should be reversed, every few years.
This will extend the life of the core by back flushing any debris that may have collect in the core, it helps prevent blockages.
Coolant protects metal parts in the system from corrosion, if part of the system is getting poor coolant flow, i.e. a blockage, then that part loses the protection and can start to corrode, then you get a heater core leak.
As simple as that is many people don't do this, I just got in the habit of doing it when I change the coolant
The warmer hose will be the outflow from the water pump to the heater core, after coolant flows thru the heater core it returns(cooler now) to the engine cooling system.
While the heater core itself has no direction, no IN or OUT, the flow thru the heater hoses does have an out and in.
While the added pump will circulate coolant when engine is off regardless of which hose it is on, I would still move it to reflect correct coolant flow direction, from the engine.
OR.......you can just reverse its direction on the hose it is on now.
As said above hoses on the heater core don't matter, they can, and I might add should be reversed, every few years.
This will extend the life of the core by back flushing any debris that may have collect in the core, it helps prevent blockages.
Coolant protects metal parts in the system from corrosion, if part of the system is getting poor coolant flow, i.e. a blockage, then that part loses the protection and can start to corrode, then you get a heater core leak.
As simple as that is many people don't do this, I just got in the habit of doing it when I change the coolant
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