the correct hookup is the hose from the water pump to the side of the core that has the valve [if original], or if you're putting the aftermarket under-the-hood style valve in, add to that input side, stopping the push of hot water into the core

Bill

Moved over to the Passing Lane

"When we tug a single thing in nature we find it attached to the rest of the world" John Muir
"When we tug a single thing on an old truck, we find it falls off" me
Some TF series details & TF heater pics & Rust-a-holics Unanimous parking lot