Trying to figure out how air bubbles are getting in my coolant and building pressure and I found something kinda odd. Yes, I’m aware it may be a blown headgasket but not willing to give up yet.

My 03 8/03 production month specifically has an aux pump that seems to be routed incorrectly usingRealOEMs exploded views.

There is a long hose coming straight from the overflow tank to the firewall as it should there is a lower tank outlet that connects by short hose to the aux pump but then goes to to a hose connected to the “hose engine inlet” which connects to the drivers side lower rear of the engine. According to the RealOEM diagram the aux pump should connect to the heater control valve, not the engine inlet. The port where the aux pump hose supposedly attaches has a hose going directly to the firewall and I assume the heater core. Oddly, all look original and nothing appears out of place or been replaced.

Simple question: should the aux pump be pumping directly into the engine or heater valve. Other plausible explanation?

Thanks.