its a water pipe. where the bottom water pipe comes out the rad it splits and one goes to round the back off the engine then it splits



the bottom pipe in the pic goes to whats missing in your pic and comes back out and the pipe that comes out sort of does a you turn back into the block or head cant realy see as it was dark in my garage lol.



hope this helps and just realised how dirty my bay has got lol new job for the weekend lol.

joe