Advantages of cooling fan after engine shutoff

[Adrian Hall]

I recently bought an old Miata and I’m looking at wiring the windows switches directly to the battery so I can raise them after putting the roof up. This got me thinking about the cooling fan. In more modern cars the fan will automatically run until the coolant reaches a certain temperature, with or without the key. I’ve looked at the circuit diagram and it seems like it wouldn’t be to hard rewire the Miata’s cooling fan that way since the relay is just controlled by a thermal switch. I’m wondering if there is any point in doing this though, since all it can do is cool the coolant in the radiator.

Any thoughts would be appreciated.

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[Stuart Tierney]

Actually, it’s not just cooling the coolant in the radiator…

If the engine is at a temperature where the fan is running, i.e; hot, then the thermostat will also be open and coolant will flow from radiator to engine block without much hindrance.

And the cooler coolant in the radiator (because the fan is cooling it) will push the warmer coolant in the block to the radiator. Rinse and repeat until things are all cooled down sufficiently. Google ‘thermosyphon’.

Same reason pretty much every turbo charger fitted as new nowadays is water cooled. Gets the heat out of there when it’s all shut down just by being ‘hot’. No pumps or timers or other such frivolity required. Just access to the coolant and it’ll cool itself down and help prevent the turbo from getting clogged with burnt oil.

None of it is strictly necessary if the operator is somewhat knowledgeable about these kinds of things and makes allowances to cool things down before shutting down the engine. But because most operators don’t know, don’t care and don’t want to make the effort to cool things down(I need to pee, NOW!) those clever folks who dream up these things have made the car be able to cool itself down without the assistance of a knowledgeable operator. Any half wit can operate a vehicle with relative impunity and little mechanical sympathy.

(But then the half knowledgeable ones get all uppity when you tell them they got suckered into something they didn’t need by some silver tongued sales jerk.)

Stu.

[Adrian Hall]

Thanks. Why do I feel like there is a story there that you perhaps somewhat bitter about :p

The temperature-induce flow thing makes perfect sense, I don’t know why I didn’t think of that before. That being the case, because I am both knowledgeable AND lazy I am going to experiment with wiring it up directly. That should be relatively easy because there are plenty of leads from the battery in the engine bay, the windows not so much.

[Stuart Tierney]

You didn’t think of it because it’s one of those things you never consider, until it’s mentioned and becomes stuck in your mind like a piece of corn stuck between teeth.

The ‘uppity’ bit comes from a specific person who we’d asked to take a look at a house for us as an ‘expert’. It was termite damaged, and worthwhile saving, but wanted a second opinion. She arrived in a very small sports car (Daihatsu Copen) and it had a turbo timer on it.

She then told us her ‘expert’ opinion on the house, which was very much CY(her)A and talking down to us like we knew nothing.

(I’m a card carrying electrician. I know a thing or two about houses and how they bolt together and I know the tools used as well, especially the locally made (Japan) ones. A shed load more than her although she’s the sales gal for a construction company…)

In the end, she got a lesson on making assumptions and I also asked her how much the turbo timer on her car cost her, which she replied $600 ‘to protect the turbo’. My stage whisper to my wife was “a fool and her money are soon parted” at which point she also learned I know how to twirl a spanner on cars and that the turbo timer was an outdated accessory her ball bearing and water cooled turbo car didn’t need.

(Ok, I learned about the watercooled turbo thing a couple weeks before. I knew newer turbos didn’t need timers so much, and then I knew why as well.)

She doesn’t outright dislike me, but she’s somewhat surprised that I’m not the same as the locals here in Japan who tend to be very good at one thing, and completely useless at anything else. I can do a few different things at varying levels of competence from ‘professional’ to ‘modern art-esque’.

It’s actually more my getting a little fed up with how they do things here in Japan and how the unwashed masses are protected from themselves, but it often ends up having the mute leading the blind. All too often you ask questions, and quickly realise you know more about the subject than the ‘expert’.

Stu.

[Adrian Hall]

I think you’ll find that’s not just limited to Japan, though I would be unsurprised to learn that it is more pronounced there.

[Stuart Tierney]

I can’t buy a bottle of ATF larger than 1l by walking into a store here.

A reliable source for spark plugs for the little car we have is further away (300km) than the factory it was built in (70km).

Your standard auto store, whatever it is and however well or poorly stocked it is has more ‘repair’ parts in it than I can buy locally, and possibly more than I can readily acquire ordering in parts. I ended up getting bushings for the front suspension for it from the middle east because I couldn’t get them locally, and if I could, I’m not allowed to know where or even get a part number.

Believe me, however bad it is where you are, it’s a whole lot worse here.

The way it’s done here does have it’s reasons and it does have it’s good points (small shop can fix all manner of cars without a lot of special purpose gear, they simply replace large assemblies not small components), but for someone who doesn’t mind (likes?) getting dirty on cars that aren’t lusted after, it’s a nightmare.

And also why new cars are so popular. Got one of them too.

Stu.

[Adrian Hall]

I just meant that people don’t like realizing that they don’t know anything here. that does sound sucky though. Canada isn’t as good as the states for that kind of thing but I CAN bike to places able to order any OEM part that I need. Almost. Not seatbelt mount spacers apparently.

[Jason Koneman]

My car has the electric fan that stays on after the car is shut off and also has an electric auxiliary water pump that pumps coolant, at least to the turbocharged. Can you do something like that?

[Adrian Hall]

[quote=”jkoneman@gmail.com” post=171486]My car has the electric fan that stays on after the car is shut off and also has an electric auxiliary water pump that pumps coolant, at least to the turbocharged. Can you do something like that?[/quote]

I probably could, but I don’t think the added weight and complexity would be worth it. That would be an interesting project though.

[Author]

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