Coolant line to heater: Which one goes to heater?

[Ninjakitty]

These are the coolant lines that run to the heater I removed approximately 10 months ago. I am ready to hook up my new heater. It specifies that the coolant travel in a certain way (inlet vs outlet).

Is there a way I can tell which one is to the heater? I don't see any specific markings. I assume that if I open either of them coolant will come out but that doesn't let me know which one is the feed.

6.6 liter New Holland diesel (1990)

 

[david.dgeorge07]

If yours is like mine, one of the lines can be traced to the vicinity of water pump. That should be the supply. A trick I used when plumbing my heater back in was to buy a length of clear vinyl tubing with the same ID from the local hardware store and to plumb it in where the heater core would be with a purge faucet.

It allowed me to see the progress of the bleeding and purging.

Something like that might help you as well.

 

[Ninjakitty]

If yours is like mine, one of the lines can be traced to the vicinity of water pump. That should be the supply. A trick I used when plumbing my heater back in was to buy a length of clear vinyl tubing with the same ID from the local hardware store and to plumb it in where the heater core would be with a purge faucet.

It allowed me to see the progress of the bleeding and purging.

Something like that might help you as well.

View attachment 28155

Thank you, that is a great idea.