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Use the Little Radiator—and Have Customers Do the Same

by | Feb 26, 2026

Disclaimer: If a car is overheating and it is possible to safely exit the road and stop the car, that should always be the first course of action to avoid the risk of fire. The solution described in this article should only be used where that is not possible.
If a car is overheating, you recommend your customer pull over and shut it down, right? Right.

But that’s not always possible. Be it a no-shoulder road, heavy traffic, or perhaps being broken down too far away to get help on foot, sometimes it becomes necessary to drive a vehicle that’s cooking away.

The following piece of advice has been hard-won through ownership of many hunks of junk, so depending on how many heaps you yourself have owned, this tip may represent obvious information or perhaps it’s a truly illuminating recommendation: if a car is overheating and it can’t be shut off, turn on the heat.

Think about it: your heater core is just a little radiator. If the big one isn’t getting the job done, throwing the heater control valve open and allowing coolant to flow through the little heater core increases both the size of the cooling system and the amount of coolant circulating (depending on the design of the specific system). Cranking the fan speed to high does the same thing as running the cooling fan wide open, albeit on a smaller scale, aiding the system’s ability to shed heat further.

The cabin may get uncomfortable. And this is obviously not an ideal solution as opposed to turning off the vehicle and finding and repairing the problem. However, if the cooling system is failing (not totally failed!) and there is still coolant in the vehicle, this may prevent the really costly repairs like head gasket replacement, or even cylinder head replacement due to warpage.

It’s no guarantee that expensive components won’t be harmed, but being aware that the heater core can also serve a cooling function does improve the odds. Tuck this tidbit away and explain it to your customers who may traverse isolated (or very heavily trafficked, ironically) areas; it may save them on the off chance they’re in this predicament.

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