Can You Identify This Coolant Hose

[Jazzadub]

Was just sent this by engine builder after topped up with coolant.

Out of curiousity, can anyone identify which coolant line this is?

I think the picture is taken from underneath the car near the starter motor.

[Ben C34]

All those should have been replaced with the engine out. That one could have used a straight piece in a loop. Woukd have cost next to nothing.

[Jazzadub]

All those should have been replaced with the engine out. That one could have used a straight piece in a loop. Woukd have cost next to nothing.

Yes in hindsight that should have been done.

So what is the line for?