Engine cooling using the heater settings
 

With my 80% grill blocking I keep an eye on coolant temps. I have noticed that keeping the internal fan off while setting the temp selector to hot will bring the coolant temp down, even under prolonged high-load hill climbing. But the reason I am posting is that I recently noticed that I can seemingly the same benefit if I select for the internal cabin air circulation. In that setting, with the heater fan off, no hot air comes into the cabin, but the coolant temp still drops. Anyone know why? I assume the heater is dumping the forced air somewhere else, other than the cabin, perhaps into the engine compartment itself.

The effect is that I can cool the engine, without using electricity for the radiator or cabin fans, and without forcing hot air into the cabin. On warm days, this will be a great benefit (if it works as well during the truly hot months).

james

I have a grill block similar to yours. sometimes my HX runs a bit hot - and when it does, it usually has trouble getting into lean burn. I keep an eye on temps of course, but I havent experimented much with using the heater to cool things down..... i'll try it for a few weeks and let you know

This is what I do with my insight.

Great. The trick with the cabin air recirculation selected but without running the fan was the biggest surprise. I expect it'll work for you too. I also found that I could set the heat level in the middle between hot/cold and get a predictably more modest effect. I like the idea of keeping coolant temps in the low and mid 190s.

my coolant temps seem to be at 183.2 or 188.3 about 95% of the time. sometimes they hover to 190. i drove to Tahoe this weekend, and found that when they were up to 190, i could lower them *surprisingly quickly* by turning on the interior heater. next time i'll try to just turn on the cabin recirculation, but no fan - i'll let u know how it turns out.

The heater valve opening lets the cold coolant in the heater core into the system. Trolla will drop the temperature gauge to cold if I open the heater valve.

Works very well
 

Today, after 10 miles driving to work, the coolant temp was up at 203* sitting at a stop light with the engine off. The temp selector on my dash was still on cold. I turned it to "hot," but with the engine still off the fan blew cold air. I started the car to drive, the air from the fan turned hot as I watched the coolant temp drop to 186* within about 10 seconds. For the remainder of my P&G routine to work the car stayed in the 180s-190s as usual (I normally have "hot" selected on the heater once the car warms up).

It was such a good example of what this thread is about I thought I'd add the story.

The coolant doesn't normally flow until through the heater core until the heater is selected. If you notice a significant drop in temps with the heater on your radiator block is too much and will lead to excessive engine wear.

I think most vehicles in last 20 years or so do not have valve for heater, instead coolant always flows and they just switch a flap to get air through heater core or to bypass it.

This would be wrong. Most engines need heater settings selected to bleed air when changing coolant.

The coolant must work through the heater coil as the pipe work acts to cool.
Would it work if you idled for a long.... period of time?
The fans rarely need to work in most commutes, as the thermostat opens, the coolant through the radiator should do the trick (and do it better than the coil in the cabin).