Any with an electric rad fan - How long does your fan run on after engine-off?

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Sun 26 Apr 2020 16:19
Any with an electric rad fan - How long does your fan run on after engine-off? - edlithgow

Ive got the fan manually controlled at the moment. This is not satisfactory and I hope to be able to restore temperature switch control presently, but meantime, I'm wondering how long I should leave it running after switch-off..

Never really noticed. Perhaps yáll didn't either, and if yiou aren't driving much in these trying times it'll be a while before you do.

I'm thinking it shouldn't be long because I tend to leave it on all the timeso its likely over-cooled while running,

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Sun 26 Apr 2020 16:35
Any with an electric rad fan - How long does your fan run on after engine-off? - thunderbird

Last car I had with a fan that ran after turning off the car was a mid 80's Golf. Frightened the life out of me the first time when after I had locked the car and walked away the fan started. A call to the dealer the next day put me strait.

Neither of out current cars (Pulsar and Fabia - both petrols) have ever ran the fan after turning off the engine but I have read on the Skoda forum that the fans runs on diesels after turning off if you interrupt a regeneration of the DPF.

On your old school 80's car I would not worry about the fan at all.

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Sun 26 Apr 2020 17:10
Any with an electric rad fan - How long does your fan run on after engine-off? - bathtub tom

An engine driven fan doesn't carry on running after you switch the engine off, so why should an electric one, normally. I can see why it would with a DPF re-gen.

You'll get more air over the radiator in normal running than any fan can generate. It's the thermostat that controls the engine temperature. I doubt if running an electric fan all the time would make any difference to engine temperature.

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Mon 27 Apr 2020 02:39
Any with an electric rad fan - How long does your fan run on after engine-off? - edlithgow

Makes sense.

OK, I'll pull the plug (literally, as it happens) when the engine is off.

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Mon 27 Apr 2020 14:08
Any with an electric rad fan - How long does your fan run on after engine-off? - Brit_in_Germany

I guess you haven't got a water cooled turbo that would need cooling after the engine is switched off.

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Mon 27 Apr 2020 09:54
Any with an electric rad fan - How long does your fan run on after engine-off? - Andrew-T

The electric fan may carry on if the engine has been worked hard in warm weather, until the sensor thinks it has cooled enough. But the waterpump will have stopped, so it will have to rely on convection while the thermostat stays open. Shouldn't run for much over 5 minutes though IHMO.

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Tue 28 Apr 2020 17:36
Any with an electric rad fan - How long does your fan run on after engine-off? - jc2

On some carburetted cars the fan came on to stop fuel evaporating in the carb when parked in the heat.

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Wed 29 Apr 2020 02:06
Any with an electric rad fan - How long does your fan run on after engine-off? - edlithgow

On some carburetted cars the fan came on to stop fuel evaporating in the carb when parked in the heat.

Hmm...we do have heat. Not a lot yet though.

Maybe on hot days I''ll leave it on for a bit, but I;d hope to have it back to automatic before high summer.

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Wed 29 Apr 2020 09:55
Any with an electric rad fan - How long does your fan run on after engine-off? - Bolt

On some carburetted cars the fan came on to stop fuel evaporating in the carb when parked in the heat.

Hmm...we do have heat. Not a lot yet though.

Maybe on hot days I''ll leave it on for a bit, but I;d hope to have it back to automatic before high summer.

If your stat is working ok there wont be any need to run the fan on- though doubt it will do much as its a standard design, if it had electric water pump it would be different ie run on would cool engine -but all yours is doing is cooling rad

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Thu 30 Apr 2020 11:52
Any with an electric rad fan - How long does your fan run on after engine-off? - edlithgow

On some carburetted cars the fan came on to stop fuel evaporating in the carb when parked in the heat.

Hmm...we do have heat. Not a lot yet though.

Maybe on hot days I''ll leave it on for a bit, but I;d hope to have it back to automatic before high summer.

If your stat is working ok there wont be any need to run the fan on- though doubt it will do much as its a standard design, if it had electric water pump it would be different ie run on would cool engine -but all yours is doing is cooling rad

Context of that comment is fuel evaporation in the carb. I'd think the fan would moderate underbonnet temperature, which might be relevent.

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Thu 30 Apr 2020 12:43
Any with an electric rad fan - How long does your fan run on after engine-off? - bathtub tom

Context of that comment is fuel evaporation in the carb. I'd think the fan would moderate underbonnet temperature, which might be relevent.

I had an (80's) Austin Ambassador - big mistake, that suffered evaporation in the carb on hot days if I stopped for a few minutes and switched the engine off. Sort of cured it by slicing open some heater hose and sliding that over the fuel pipe and wrapping the lot in ally foil.

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Thu 30 Apr 2020 16:23
Any with an electric rad fan - How long does your fan run on after engine-off? - Bolt

I'd think the fan would moderate underbonnet temperature, which might be relevent.

Depends where the carb is in relation to fan, the fan doesnt force air around engine only push or pull air through radiator which is all its designed to do.

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Thu 30 Apr 2020 16:39
Any with an electric rad fan - How long does your fan run on after engine-off? - thunderbird

Mate had a Renault 5 GT Turbo in the 80's. They were not exactly state of the art, big turbo stuck on a 1400 push rod engine and still fuelled by a carburettor. Renault had fitted a fan that cooled the turbo for a set time after the engine was turned off to stop it cooking the oil.

Fortunately things have moved on since then.

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Fri 1 May 2020 02:57
Any with an electric rad fan - How long does your fan run on after engine-off? - edlithgow

Mate had a Renault 5 GT Turbo in the 80's. They were not exactly state of the art, big turbo stuck on a 1400 push rod engine and still fuelled by a carburettor. Renault had fitted a fan that cooled the turbo for a set time after the engine was turned off to stop it cooking the oil.

Fortunately things have moved on since then.

Seems like a reasonable work-around. What have they fortunately moved on to?

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Fri 1 May 2020 02:54
Any with an electric rad fan - How long does your fan run on after engine-off? - edlithgow

I'd think the fan would moderate underbonnet temperature, which might be relevent.

Depends where the carb is in relation to fan, the fan doesnt force air around engine only push or pull air through radiator which is all its designed to do.

The air has to go somewhere after it has traversed the radiator. Quite hard to see how it wouldn't flow around the engine (certainly does on this car).

Maybe in a modern crowded engine compartment it might be ducted somewhere else, dunno.

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Fri 1 May 2020 08:18
Any with an electric rad fan - How long does your fan run on after engine-off? - jc2

There were some vehicles that ran the fan backwards for this after-cooling-ie.suck hot air out.Then they started fitting return fuel lines-cheaper!

Edited by jc2 on 01/05/2020 at 08:22

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Fri 1 May 2020 10:11
Any with an electric rad fan - How long does your fan run on after engine-off? - Bolt

I'd think the fan would moderate underbonnet temperature, which might be relevent.

Depends where the carb is in relation to fan, the fan doesnt force air around engine only push or pull air through radiator which is all its designed to do.

The air has to go somewhere after it has traversed the radiator. Quite hard to see how it wouldn't flow around the engine (certainly does on this car).

Maybe in a modern crowded engine compartment it might be ducted somewhere else, dunno.

Once engine is hot it is pushed down under car as it has nowhere to go helping the sump cool, some carbs had heat diverters to help prevent fuel evaporation though not all worked as the plates were too small on some cars. the thought was there though lol

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Fri 1 May 2020 11:28
Any with an electric rad fan - How long does your fan run on after engine-off? - aethelwulf

Well, my 1986 Transporter (VW) Turbo Diesel had a two stage fan that worked after engine switch off if the water temperature was high. This made a colossal noise on stage two. This was to cool the oil/turbo. It also had a bypass electric water pump which continued to operate after the ignition was off in case of overheating. The water system was complicated with the engine at the back and teh radiator at the front and gave plenty of aggro in the 20 years that I owned it. But it was designed as an air cooled vehicle and then had a Golf diesel engine stuck in and the cooling system never seemed to be up to the task, especially in the Pyrenees.

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Sat 2 May 2020 05:01
Any with an electric rad fan - How long does your fan run on after engine-off? - edlithgow

I suppose if carb perc-ing was a problem one could perhaps fit a supplementary fan, something like a computer case fan, which should be cheap and not draw much current. AFAIK it isn't a problem though.

The rubber sealing strip at the back of the bonnet came off and I have probably now lost it. This might reduce underbonnet temperatures a bit during cool down

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