Let Engine Get to Operating Temp, Then Run Heater?

Hello All

I live in the Midwest. Years ago I read an article in the local paper that advised that in the winter, when you first start a cold engine, you should keep the temperature control for your heater turned all the way to the cold position until the engine had reached it's normal operating temperature. Then, at that point, you could turn on the heat in the cabin. The reasoning given was that you didn't want to divert heat from the engine until it reached its full operating temperature.

I've pretty much followed that advice based on reading that one article years ago. But reading some of the posts in this newsgroup got me wondering if I am following one person's well intentioned, but misinformed advice. . Is there a sound mechanical reason for keeping the heat off in the car's cabin until the engine is fully warmed up?

Thanks.

KC

Reply to
KC
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Well, the heater core from which the heat is dissipated into the cabin of a car is indeed a small radiator. Using the blower while the engine is not up to operating temperature will divert heat from the engine. The heater core gets the coolant from the cylinder head and then the return line goes directly to the water pump; hence, your heater will work regardless of whether you have reached operating temperature or not (thermostat on or off). Nonetheless, I am not sure how much heat is dissipated by the heater core; I suppose it depends on how large yours is. I don't think the advice is bogus, but if you have a car with a small heater core, trying to get the cabin as warm as possible might be worth it the extra 30 seconds for the car to come to operating temperature.

- JR

Reply to
JR Lomas

Many modern cars don't shut the water off to the heater core even if the temperature control knob is turned to cold. All this does is change the position of the blend door that controls the mix of air through the heater core and evaporator. This will reduce the amount of air through the heater core and might help the engine warm up a little faster, but the difference is probably trivial (assuming the main engine thermostat is working as designed). There are still some vehicles that include a water control valve. When you move the heater control to full cold, these vehicles interrupt the flow of water to the heater core, so they may allow the engine to warm up a little faster.

Ed

Ed

Reply to
C. E. White

The amount of heat that the heater core can reject is so small compared to the radiator and the amount of heat that the engine generates that I doubt that running the heater full blast on the coldest day would delay engine warmup by more than a minute, if even that much.

Enjoy the heat.

JazzMan

Reply to
JazzMan

I thought that neither the heater nor the radiator get any warm coolant until the thermostat opens which would be when the engine reaches the operating temperature.

Regards,

Boris Mohar

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Ontario

Reply to
Boris Mohar

Most vehicle always send coolant through the heater core becasue the heater core inlet hose is before the thermostat.

Ed

Reply to
C. E. White

Maybe a comfort reason. If you turn on the heater and fan before the engine warms up, you and your passengers get a blast of cold air. Not much of a problem in Southern California, but a bigger issue in the Midwest.

If you have a car that is cold-blooded or slow to come up to operating temperature, leaving the heater off while warming up might make a difference. For most cars, it isn't a concern.

Reply to
Christopher Green

My '85 Colt would never warm up, if I let it idle in very cold weather with the heater fan at any setting other than the lowest.

Reply to
Mark Olson

Well, I generally don't turn the fan up until the engine has warmed up some, since there's no point in blasting cold air into the car. I guess that does let the engine warm up faster as well, but waiting until it's entirely warmed up is probably overkill.

Reply to
Robert Hancock

Thanks all for the responses. I should have phrased the question better. I wouldn't turn on the heater when the engine is totally cold (as one poster said, what's the point), but rather when the engine has some heat in it but has not yet reached operating temperature.

Sounds like it's not a detriment to the engine to run the heater before the engine is at full operating temperature.

Thanks again everyone.

Reply to
KC

Today`s cars always send coolant to the heater core. Some 25 years ago, the heater hoses were routed in such a way the thermostat had to open first to send coolant flow to the heater. Back then it took quite a while before the coolant was hot enough to open the thermostat to eventually heat the cabin.

Reply to
Daniel

I've never seen any such vehicle. All the "big 3" American makes (and I can say this with certainty back to the immediate post-war cars) tapped the heater water off upstream of the thermostat. Certainly true for my '49 Plymouth and ever car I've owned since...

Reply to
Steve

I agree with what you are saying below. I did not write the above paragraph, even though you attributed it to me.

Ed

Reply to
C. E. White

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