I don't think that's how it works. For example, my 302 has small bypass hose, from the water pump, to the thermostat housing. A small amount of coolant is always circulating, even with the thermostat closed. So the coolant in the radiator might not be 180, when the thermostat opens, but it's NOT 20*, or what ambient temperature is.

 

Aye.

The flow is from the top of the engine, through the radiator, and into the bottom of the engine.

A thermostat starts to open at the rated temperature and is fully open 15-20° over that, and it's a sort-of slow process.

Stant :: FAQs

Any cold water poured into the top of the radiator will circulate through the radiator to the bottom, where it will then be sucked into the engine and circulated through the water jacket before it comes out the top; no ice-cold water will ever come near the thermostat.

Coolant is always flowing through the engine's water jacket and, likewise, through the heater core regardless of the thermostat's position unless one specifically disables that function (and some more modern engines come equipped with a facility to block/unblock that flow through the heater core at certain times).

 

Like I said, the heater loop is *always* bypassing the thermostat.(so there are no stagnant hotspots in the block, heads or intake)
The coolant is always tempered by the slow opening (and closing) of the thermostat.

At -40* it's going to take a long time to get #600+ of iron up to 225*.
Over cooling becomes an issue where you might want to restrict flow.
I have fortunately never seen it so cold my coolant changed to slush.
That's just crazy to be outside in -50 or lower!!!

 

Chris,
most "modern" engines with heater shutoffs just reroute the coolant before the heater core.
They don't deadhead the system.

Have a look at the four port vacuum controlled heater valve found in the later Rangers.

 

Well then how about you explain why when I was using a water hose to put water in the engine that was already heated up why was the thermostat open for about 2 minutes then closed for nearly 5 minutes before opening up again if the water reguardless of how cooled it is will be warmed up before it gets to the thermostat.


I love to hear your reason because I visually saw this as water came out of the upper hose and then stopped then started up again as the thermostat opened up. I have also seen this happen on every late model vehicle I work on that I do a coolant flush on and they all work like this.

 

I never said anything was dead-ended, did I? That wasn't what I was trying to say - only that some of the more modern configurations won't route heat into the passenger compartment (via the heater core) during certain situations - say, when some sort of valve system controlled by the HVAC panel prevents that.

We're saying the same thing - coolant always flows through the engine regardless of the thermostat position, but "it depends on other stuff" if it goes through the heater core or not. yes, those valves have been around for a while; some factory configurations have them (mostly GM products I'm familiar with), the aftermarket has had them for a long time.

 

For one thing, in your scenario, you do not have a closed system. You are continually adding COLD TAP WATER to the system. With a closed system, the water will start heating up once the engine starts. It will also start circulating, EVEN WITH THE THERMOSTAT CLOSED, through the heater circuit, and through the bypass hose. The coolant continually heats up, and circulates through the system with the engine running, just not at the flow that would happen when the thermostat is open.

 

Nope doesn't matter even when I had the system as a closed loop when it was 38*F one morning on the way to work the engine was at the normal mark on the gauge it always runs at when I started moving down the road the temp gauge dropped almost to the C mark. This position is the same position it goes to when the thermostat closes because it is below 180*. So even in a close loop system if the air going over the radiator is cool enough it will cool it down enough that the engine will never keep up with the over cooling aspect.

 

Wait a minute...

The claim was that cold water added into the top of the radiator causes the thermostat to "slam shut" and this claim has been disputed by several others here.

And now we're ignoring the water and instead adding dash gauges and air movement to the argument?

This thread is done.