I'm thinking off adding something like this in the inlet/supply hose off the cylinder head, like you guys did. 

It'll be for keeping the coolant from going into the heater core and no pressure on the heater valve.  The heater valve I bought from Nissan has a plunger with rubber around plastic.  Looked a little rinky dink to me.

Edited June 11, 20177 yr by siteunseen

@sweatybetty

@Captain Obvious

Could you guys give me a rough capacity level for the coolant on the heater core? It's a 240 if they're different sizes from the 280s.

I was pretty scattered but I think it held close to a half a gallon. That's hoses and all. It ran close to fifteen before I put the cap back on to build up some pressure. No leaks and the gauge was where it always is. 

Does that sound about right? Thanks for any replies/help. 

 

I would definitely add a ball valve like you pictured in the engine compartment. You could probably keep it completely closed for most of the year and only need to crack it open at the very beginning and end of the season. Speaking of which... I could probably close mine down now. I don't think I'll be needing heat until maybe October.

As for the capacity of the heater core, I haven't measured it, but I don't think it's even as much as a half gallon. Maybe between a quart and a half gallon?