Heater core & heater valve - which comes first?

[Ron Kwas]

Simon;

At the CVI linked page I see "Elbow union, water return pipe B18/B20 (at back of cylinder head)"...I have to point out, as a result of our investigation, that this is also incorrect...it should more correctly be called a send, or source, or supply pipe. Picky...Picky...

Cheers

[Derek UK]

Originally Posted by Ron Kwas

Derek;

I don't think I can agree with your premise that HCV first or HC first would make a difference in how quickly heat was available from HC. "I'm reminded that the matrix will tend to be hot all of the time." I think this can only occur with a HCV which is not fully sealing, allowing some limited flow in the loop (and HC to be warm). ...but presuming a properly working HCV, that means zero flow in the Heater loop, and that means even when engine is hot, the coolant in the entire Heater Loop is static and therefore remains at ambient.

What do you think?

I think it has to be more than ambient after the engine has been running for some time. It is directly supplied from the head, so at full running temp the heat must transfer through the fluid to some extent even if it isn't actually flowing. I did say it would heat up quickly when the valve is opened.
As Simon says (sic) not worth worrying about.