Doesn't do that for the turbo, as the engine itself is not running and pumping the air.
What is does, is, for turbos that are water cooled, it circulates the coolant via auxiliary pump to cool the turbo down, to prevent oil coking in the bearings.
Usefulness of running radiator fans after shutdown?
- Thread starter Avery4
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What is does, is, for turbos that are water cooled, it circulates the coolant via auxiliary pump to cool the turbo down, to prevent oil coking in the bearings.
I recently ran across this video of someone making a clear thermostat housing and it's quite interesting to see the very obvious thermosiphon that eventually forms after shutting off the hot engine at around 18:40. I never realized the flow was so dramatic, I imagined it being incredibly slight, but with that much flow, continuing to run the fans after shutdown likely would be helpful.
As far as heat soak is concerned, I think the most effective prevention for most of us is probably to just go very easy on the engine for a few minutes before shutdown to give the pistons, cylinders, heads, oil, coolant, exhaust, turbo (if equipped), etc time to cool off, therefore minimizing heat soak and its nasty consequences. In most cases this won't require any deliberate action, but I know people who frequently shut off their engine seconds after very aggressive driving and I can't see that being healthy for any engine.
As far as heat soak is concerned, I think the most effective prevention for most of us is probably to just go very easy on the engine for a few minutes before shutdown to give the pistons, cylinders, heads, oil, coolant, exhaust, turbo (if equipped), etc time to cool off, therefore minimizing heat soak and its nasty consequences. In most cases this won't require any deliberate action, but I know people who frequently shut off their engine seconds after very aggressive driving and I can't see that being healthy for any engine.
SammyChevelleTypeS3
$50 site donor 2023
I knew several private and even some dealership master mechanics who told me they had for years been in the habit of parking their cars and trucks in the garage and popping open the hoods to help speed up cool down. They felt it could just in general extend life of just about everything including sensitive electronics under the hood. Certainly can not do any harm. Just make sure to chase your cats off the engine.
Mine like the heat so much I often find them sleeping on top of a warm hood or even on top of the engine if/when I pop the hoods on really hot days after a drive. I had a car about 20 years ago that I could hear the temp controlled fans kicking on and off for a short while after a drive when it was a really hot summer day.
Since there are a ton of cars out there, that don't do this "after bow", and even more cars that don't have an electric fan at all (and they are all still working just fine), I guess the answer isn't that simple.
My 20+ year old Volvos do the following:
1. Afterblow - 45 minutes after shutdown, the AC blower comes on, runs for 5 minutes and dries out the evaporator. Keeps it clean, prevents musty smell. Works great. Happens every time.
2. Cooldown - If the engine is significantly above normal temperature, the radiator fan comes on and cools the engine compartment for several minutes. Because the gauge is compensated to read in the middle, I can’t tell you at what temperature this happens, but in the summer heat, it’s not uncommon.
Before folks talk about dead batteries, and I understand the concern, the OEM battery in each of the cars lasted ten years. Ten. Years. Keeping the battery in the rear of the car, out of extreme heat adds a lot more to battery life than running a fan takes away.
I've only seen the (condenser) fan run after shut down on the Legend once in +20 years. It's wired into an oil temperature sensor in the rear head cam cover. The fan operation is controlled by a black box.
Decades ago, I remember a vintage FWD, x-verse mounted vehicle (Datsun? Ford?) having a small (like a PC cabinet) cooling fan mounted in the corner of the firewall that blew air across the engine.
Decades ago, I remember a vintage FWD, x-verse mounted vehicle (Datsun? Ford?) having a small (like a PC cabinet) cooling fan mounted in the corner of the firewall that blew air across the engine.
Interesting, thanks for sharing. I know many older Honda/Acura vehicles will leave the cooling fan running with the ignition off if the engine is hot enough to trigger the fan switch. They have a fan timer module and will run the fan(s) either until the engine cools off enough for the temp switch to shut them off or until the fan timer shuts them off.
I wonder why Honda/Acura stopped using that system in the early 2000's. I'm guessing probably just a cost cutting measure.
A different fan. Some Cadillacs used to do that to help prevent mold growing inside of the AC evaporator but they ran the AC blower fan not the radiator fan. I doubt that running the radiator fan would do anything.
Or it just didn't do anything significant.
The correct term is thermo-siphon. Coolant isn't actively pumped around the system and the circulation is driven only by the difference in the temperture of the heated coolant vs the cooled coolant. See Thermo-syphon Cooling System. Many cars and other power plants used it at one time but since the coolant only flows slowly, the size of the cooling system and the amount of coolant required were enormous and it's rarely used today.
Could be, the vehicles they made without it are obviously doing fine. I just assumed the engineers probably had a good reason for creating the fan timer system and using it for well over a decade.
It also could be that improvements in fluids, gasket materials, rubbers, plastics, etc reduced heat soak concerns enough that heat soak just isn't much of an issue anymore.
My Kawasaki, and every other water cooled bike I owned would only kick the fans on after stopping if I killed the bike with the run/stop switch on the handlebar and left the key in the "on" or "run" position.
If you shut the bike off with the key - it would kill the fans.
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So did my sister's husband's parents. That would've made sense after a long run in hot weather, but it stupidly did it even after short winter trips, resulting in chronic battery problems.
My Mazda had no such feature, but after stopping on hot days I sometimes left the (front-hinged) hood ajar.
Ditto @Astro14 . The p2 Volvos I had would do both the “afterblow” and the engine cooling fan. There were certain conditions that had to be met… healthy battery, at least 5 minutes of AC time, and relevant engine and exterior temps.
the rad fan generally didn’t trigger unless the heat soak was hard, like manual shifting the little beast up a hard mountain climb to a ski slope cabin in July. And, the rad fan was much more potent while being quiet than the 80s vehicles I had that did this.
the rad fan generally didn’t trigger unless the heat soak was hard, like manual shifting the little beast up a hard mountain climb to a ski slope cabin in July. And, the rad fan was much more potent while being quiet than the 80s vehicles I had that did this.
SammyChevelleTypeS3
$50 site donor 2023
Guess it likely boils down to stuff like: one guy uses only top tier gasoline and never ads any gas additives or injector cleaners. Another uses cheapest gas he can and uses injector cleaners. They both go long times with no fuel related issues. Who is right? And so on with so many things....
My GTI makes all kinds of noises after shutdown. I think both the fans and water pump are running, mostly to cool the turbo.
If it's been idling on a hot day, I try to remember to run the heater for a few minutes before shutdown. In the past, I ran a pedestal fan to blow air into the grill for a few minutes after parking in the garage until I realized this does little to nothing helpful.
If you have an electric fan, turning on the AC for a few minutes to force the fan on will likely be more effective at removing heat from the radiator and engine compartment since the heater core's heat dissipation capacity is tiny compared to the radiator and it doesn't blow any air through the engine compartment.
If you have a fully mechanical clutch fan, turning the heat on to help remove heat from the cooling system will be marginally helpful though because less heat in the coolant will mean cooler air through the engine compartment.
When I was much younger and very bored, I installed a switch inside my 05 Civic to force the radiator fans on and still sometimes use it in hot weather to cool things off for a couple minutes before parking it just because I can and it doesn't introduce more heat like turning on the AC to activate the fans will, although the benefit probably isn't significant enough to justify installing a switch just for that purpose.
4WD
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Interesting comment - I have been watching oil temps in the Jeep and unlike my old H3 wondered why they bothered with fake hood vents - I came up with a $20 idea to make them active and still drain rain water to the fenders …
So far 8° on the highway and 6° lower on sand pulls - have room to add more relief …
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