Heater Core Line Routing

[Brewer]

I have an inline filter I'd like to install, and I think I know which line to install it in, but I'm not 100% and can't seem to find a definitive answer online, so thought I'd ask here.

The line circled in green in this pic is the line-in for the heater core, right? (it's the top line going into the firewall from the engine compartment).

The line circled in red would be the return line from the heater core (the bottom line coming out of the firewall). Correct?

I'm not sure because on my old 4th gen, a mechanic installed an inline filter on the line circled in red. Which seems not right to me.

Anyway, thanks! I'm running a 2024 with the HO cummins.

 

[dieselscout80]

Before the heater core would be best in my mind.

If you do a cold start you can hold your hands on the lines to the heater core and see which one warms up first (input side).

 

[mtnrider]

Here is your answer, The inlet to the core. Where that "mechanic" installed it in the red circle is the Wrong place and isn't going to do you any good.

 

[ginokaan]

Red one is exhaust pressure sensor and connector means wrong