Heater Core Hose Replacement

[takeyourmarx]

This might be a silly question, but I’ve learned to swallow my pride and ask the dumb ones, hah.

 

I’ve just rebuilt my heater box (which became way more involved and expensive once I found out the valve was missing, bracket broken and fan was dead) that was sitting in the trunk of my 02 when I bought it.

 

I have it mounted back up in the car,  but before I yank off the bypass coolant hose that is looping back, do I need to drain the coolant out of the car? The water valve should prevent it all from coming out, right?

[Son of Marty]

If it was just reconnecting the heater core you'd be fine, but if you have to remove the hose off the back of the head or the return pipe you should drain the system at least part way.

[takeyourmarx]

Ok thanks, that’s what I needed to know. The current bypass is just a singular piece of hose going from the outlet flange on the back of the head right to the inlet flange on the other side of the head.

 

So seems best to at least drain until its level with those two places.

 

Might be best to do the whole thing though since I’m not 100% the coolant that’s been in there is the right stuff anyway.