Ask The Editor: Fanning My Hot Engine
Who needs liquid cooling anyway?
So to help it out I’ve been putting 2 box fans right near the engine to help it cool after. I hadn’t thought about it but my mom asked if cooling it down too quickly could be bad for an engine. And since I don’t know I thought I’d ask here.
Any harm in using my method to cool an engine down much more quickly than normal?
Here’s the good news- circulating ambient air around an engine externally will do no damage whatsoever. In fact, this is the primary means of lowering engine temp in all air-cooled machines, is what happens when we shut our machines off on a cold windy day and is exactly how your engine returns to ambient temp in general (just across a slightly longer span of time).
From a physics standpoint, blowing a fan upon something hot isn’t cooling the object at all (unless the air itself was colder to start with, like from an air conditioner for example). What it is doing is displacing (pushing away) heat, thus allowing the hot object to reach ambience quicker than if it were to shed its heat into stagnant air.
The bad news is that you’re likely doing little more than wasting electricity running the box fans. If the engine is overheating in operation, it’s going to overheat again the moment you get it running again and if it’s running okay as you said, blowing air upon it to speed up what will happen anyway makes very little sense.
If it’s because you plan to start it again immediately after, keep in mind that the culprit likely has almost nothing to do with the engine you’re trying to cool down. The most common cause of a slow hot crank is the starter itself. As the brushes and the armature in the starter wear down, heat binds them. Replacing your machine’s starter will cure hot weather slow starting in this situation. Additionally heat can play havoc with electricity’s ability to flow. If you notice a big change in starting oomph whenever it gets hot, consider replacing the positive battery cable. Heat can exaggerate the amount of internal resistance in a failing battery cable.
