On Sat, 8 Jul 2017 20:03:26 -0700 (PDT), trader_4
wrote:

On Saturday, July 8, 2017 at 10:40:53 PM UTC-4, Vic Smith wrote:
On Sat, 8 Jul 2017 21:46:08 -0400, Ed Pawlowski wrote:

On 7/8/2017 8:58 PM, Vic Smith wrote:


No it's not misinformation. Anybody who's ever replaced a heater core on GM vehicles that
I know of, know that the core has an inlet and outlet and no valves restricting flow.
It's the job of the mixer door to adjust heat in the cabin. There are some vehicles that
have heater water valves, but I haven't worked on them.
And their is no "extra" heat.
Engine designers can't eliminate waste heat until they design one that's 100% efficient.


It has been probably 40 years since I played with heater cores, but I do
know there was a valve in the line to stop the flow. Maybe thing have
changed?

https://www.yourmechanic.com/article...hard-zeppetini

Google heater core valve and then click on images.

This is GM specific
https://www.google.com/search?q=heat...w=1366&bih=638

Like I said, "There are some vehicles that have heater water valves, but I haven't worked
on them." I've owned only Chevy cars and one van, and a Grand Am since about 1975.
NONE of them had a heater valve. Nor did my 1966 F100 Ford PU, or 1973 Dart.
Pretty sure you'll find that cars without heater water valves are as common as Chevys.

Maybe you just need to look harder?

http://www.ebay.com/itm/HVAC-Heater-Control-Valve-Heater-Valve-Front-4-Seasons-74603-/272744018440?fits=Make%3APontiac|Model%3AGrand+Am& epid=75725794&hash=item3f80cf7208:g:BhoAAOSwq7JUAT Wl&vxp=mtr

If you give us the year for the vehicles in question
we can look at accurate part info. But just googling
for Pontiac Grand Am, looking on Ebay, etc obviously
at least some of them used heater valves.

This has really drifted off topic Even if there was a valve, it only
stops one direction of flow and since the system is pressurized a leak
in the heater core would still drip, coming in from the other side.
Yes I have had a leaking heater core and the only way to stop from
steaming up the car is to pipe around the heater core as mentioned in
a previous post. I got rid of my 75 Monza for exactly that reason.
Replacing it would have involved removing the whole dash according to
the Chevy dealer. It was OK all summer but I was not going into a DC
winter without a heater.