Any info on keeping my Electric Fan on for 15 min after shutdown?

I've read thru upteen hundred threads on adding electric fans, but can't find any info on what I'm looking for.

On my '01 XJ I'd like to be able to run the electric fan for about 5-15 minutes (not sure on exact time needed) after I stop during the Summer. I have been experiencing some vapor lock after idling in traffic and the heat build up due to slow driving. In lieu of adding hood vents (at least not yet) I'd like to try and push that heat out of my engine bay by running the fan for a bit, similar to a Turbo Timer of sorts.

Has anyone done this or does it seem like a bad idea? I'm always open to suggestions.

Thanks.

IMO using a low current draw fan after shutdown for 5-10 minutes should be fine. A battery (good battery) should be able to handle that load just fine. Your only problem is going to be it shutting off by itself. The only options I see are: 1) actually using a Turbo timer and just wiring up the timer for powering the fan, instaead of the ignition switch. Or, 2) use a coolant temp switch for your power and have the fans shut off at a certain temp. But that would use a constant 12 volts even with the vehicle off...

Here you go!

http://www.at-fairfax.com/P1786-ELK-960.htm

I have been using an ELK timer for several years to combat warm weather heat soak.
http://www.flickr.com/photos/lwade/sets/72157617434915718/
Three minutes is enough time to dissipate the excess heat rising off the 2001's mini-catalytic converters, preventing the seat soak stumble.
The ELK can be set to operate for up to an hour.

Thanks all. I'll have to look into this.

lazyxj... are you running any vents or just the timer to run the e-fan after shut-down?

If you're handy with electronics you can make your own circuit with a simple relay, and some other parts. Link on how to.

Redsnake said:

are you running any vents or just the timer to run the e-fan after shut-down?

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Just the timer. Three minutes is long enough to eliminate a good portion of the heat pouring off the exhaust and the vapor-lock like symptoms.
Hood vents may help but I have never heard of anyone solving the hot soak problem with vents alone.
Good luck.

In my case, the water pump runs on for two minutes or, a drop of 5C degrees below setpoint. You would be amazed at how much heat is transferred even without the fan running. Should the system see the temp heat spike after shutdown to 3C above setpoint, it runs the fan as well during the after run event.

How does this help since the coolant is no longer moving? It seems like it would move some air under the hood but how much cooling can it really do? Wouldn't you be better off putting the fan on a switch and turn it on five minutes before shutting it down?

bert01xj said:

How does this help since the coolant is no longer moving? It seems like it would move some air under the hood but how much cooling can it really do? Wouldn't you be better off putting the fan on a switch and turn it on five minutes before shutting it down?

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The idea is that the pre-cats on the 00-01 Model XJ's retain a LOT of heat and they sit right under the intake and fuel injectors and fuel rail. When you shut down and park that heat sits in the pre-cats and in turn 'cooks' the fuel in the rails and injectors that is no longer being pumped thru the engine. The idea is that if you keep the fan running for a few minutes it's enough to push that hot air out and keep the convection process out enough so the fuel doesn't vapor lock. Same idea w/hood vents or having an electric water pump to continue to circulate coolant after shut-down. I'd be willing to pay money for a 'simple' 'plug-in' application to keep the fan running as I'm not sure I'm smart enough to wire in the switch/circuit that's been referenced here. I may give it a go and see what happens...

bert01xj said:

How does this help since the coolant is no longer moving? It seems like it would move some air under the hood but how much cooling can it really do? Wouldn't you be better off putting the fan on a switch and turn it on five minutes before shutting it down?

Click to expand...

Its hard to argue with success. The timer method has years of experience to prove that it works. The electric fan blows a lot of air and the hot air does not stay in the engine bay.
The big problem is the heat pouring off the exhaust. Exhaust systems are designed to dump heat quickly, so it does not take long to get rid of a large amount of it when using forced air cooling.