You are correct, it is a return line from the AOS. The inside diameter of the plastic fitting is smaller than the inside diameter of the hoses. The ID of his Home Depot hose splicer looks to be about the same as the ID of the hoses (the brass is thinner than the plastic, and the hoses are stretched a little to fit). So it seems plausible that the new fitting flows better — but I agree, it wouldn’t seem like a huge amount of coolant ought to be passing through there.Kalashnikov wrote: ↑Sun Jul 15, 2018 11:37 am That line is a coolant return line from AOS if I remember it right. It is tiny in diameter to start with. I doubt it has any effect on cooling whatsoever.
This whole thing started when my buddy was replacing his alternator and broke that stupid plastic thing. Maybe the new alternator has less drag and his water pump is working more effectively.