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Radiator Fan- Automatic Running for Cool Down

CobraMarty

CobraMarty

NAXJA Forum User
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PM me any questions
When I park and turn off the engine, the under hood temperatures soar!! And I get terrible 'heat soak'.

Would running the radiator electric fan for say 5 to 10 minutes, after turning off the engine, helping to move the air thru the engine bay and helping to get all that hot air out of there so that there is less heat soak?
I already have a hood vent and the rear of the hood spaced up.

Any thoughts or ideas?
I reconfigured a 'turbo timer' so that when you turn off the engine, the electric radiator fan will turn on and run for adjustable 0-10 minutes.
 
I just put a painless thermostat switch with a 5 post relay wired in. When the engine is turned off the fan will start about 2 minutes (if it is not running before that) after and turn off when the temp reaches 185*. The e-fan doesn't run for more then 10 minutes on a hot day.

I have yet to have any problems.
 
Hayden Temp Probe

Yes I'm going to do this too - you can get a Hayden Temp probe which goes through the radiator between core tubes in many different temperature settings. I will use the probe to trip the oem relay in my fuse block for the fan.

I have not started this yet so I'm not sure if I will have to "flip" the signal from ground to +12v with a bosch relay.

Either way, I'm with you, and it will also turn the fan on sooner than the PCM is - which I feel waits until things are already a whole lot hotter before finally engaging. I think I will try the Hayden 3652 - they do have adjustable ones also.

41Xa7p3GQVL._SL500_AA300_.jpg
 
Last edited:
I'm not wanting to turn the fan on earlier 180-185* when the engine is running. And when the engine is off, the water pump is not turning, there is no circulation of coolant when the engine is off, so turning the fan off when the cooling is at a certain temp(on it's way down from 210 to 185*) is not what I was after.

I just want the fan on to blow/circulate air thru the engine bay when the engine is off. Sure a 'by product' of this is that the coolant sitting in the radiator
right in front of the electric fan will be cooled off, but the rest of the coolant and engine will still have hot coolant.
 
CobraMarty said:
I'm not wanting to turn the fan on earlier 180-185* when the engine is running. And when the engine is off, the water pump is not turning, there is no circulation of coolant when the engine is off, so turning the fan off when the cooling is at a certain temp(on it's way down from 210 to 185*) is not what I was after.

I just want the fan on to blow/circulate air thru the engine bay when the engine is off. Sure a 'by product' of this is that the coolant sitting in the radiator
right in front of the electric fan will be cooled off, but the rest of the coolant and engine will still have hot coolant.
Click to expand...

Hmm and I guess initially you will be blowing really hot air until the coolant in the rad comes down.
 
I did the dirtbound offroad e fan swap.
I set the fans to run after shutdown on my wife's 01. (temp controlled, averages 8 minutes, 4-5 with both fans running, the last few with just the center one, ambient temp of 80)

It doesn't make a ny difference in a heatsoak situation.

Slow crawling in the heat, shut it off, fuel still bols in the rail.
I had to purge the air/vapor out of the rail to get it to start.

returnless fuel system just bites.
 
Re: Hayden Temp Probe

X E Ryder said:
Yes I'm going to do this too - you can get a Hayden Temp probe which goes through the radiator between core tubes in many different temperature settings. I will use the probe to trip the oem relay in my fuse block for the fan.

I have not started this yet so I'm not sure if I will have to "flip" the signal from ground to +12v with a bosch relay.

Either way, I'm with you, and it will also turn the fan on sooner than the PCM is - which I feel waits until things are already a whole lot hotter before finally engaging. I think I will try the Hayden 3652 - they do have adjustable ones also.

41Xa7p3GQVL._SL500_AA300_.jpg
Click to expand...

if you disconnect the stock wiring completely it will cause the ECU to throw a code, hense the 5 post relay that I am using.

Wiring up the E-fan helped with my Heatsoak issues, along with hood vents
 
I have had both my jeep, a 97, and the wifes, which is a 98, e-fan wired directly to a toggle switch with a fuse in line and have not had a code come up in three years. Only crappy part is having to remember to turn on the switch once you hit the trail, the clutch fan just can't keep up after a half hour or so on the trails.
 
CobraMarty said:
When I park and turn off the engine, the under hood temperatures soar!! And I get terrible 'heat soak'.

Would running the radiator electric fan for say 5 to 10 minutes, after turning off the engine, helping to move the air thru the engine bay and helping to get all that hot air out of there so that there is less heat soak?
I already have a hood vent and the rear of the hood spaced up.

Any thoughts or ideas?
I reconfigured a 'turbo timer' so that when you turn off the engine, the electric radiator fan will turn on and run for adjustable 0-10 minutes.
Click to expand...
I have been running a fan timer for several years on my 2001 xj (with the dual mini-cats). The timer is set by pushing a button and it runs the electric fan for about three minutes, long enough to eliminate the hot soak mis-firing problem. I use the button to activate the timer only in hot weather. In the winter, it isn't needed.
http://www.naxja.org/forum/showthread.php?t=1028190&highlight=fan+timer

Recently I insulated the bottom of the intake manifold, eliminating most of the problem.
 
Nice, but I want it to be totally automatic. Turn the key off and the fan comes on for set time, 0-10 minutes.

I rewired/reconfigured the turbo timer and it is ready to install. The control head has digital screen and it has 2 different timers. Timer #1 can be 'summer' 10 minutes, timer #2 can be 'winter' 3 minutes, and it can be turned off completely.
 
CobraMarty said:
Nice, but I want it to be totally automatic. Turn the key off and the fan comes on for set time, 0-10 minutes.
Click to expand...

For others who want to do this, an ELK-960 timer and a standard 12-VDC 5-pin Bosch-type can be wired to provide automatic operation.
Wire so that the relay's coil is powered when the ignition is on. When the ignition is turned off, have the contacts close and ground the timer's trigger (trigger set to negative).
The timer can be adjusted to run from a few seconds to 60 minutes.
Once the ELK times out, no power is used.
A SPST switch can be added to the coil's power supply wire to stop operation during cold weather or any time operation is not desired

The ELK-960 has proven to work trouble free for several years and the price reasonable at $30.
 
lazyxj said:
For others who want to do this, an ELK-960 timer and a standard 12-VDC 5-pin Bosch-type can be wired to provide automatic operation.
Wire so that the relay's coil is powered when the ignition is on. When the ignition is turned off, have the contacts close and ground the timer's trigger (trigger set to negative).
The timer can be adjusted to run from a few seconds to 60 minutes.
Once the ELK times out, no power is used.
A SPST switch can be added to the coil's power supply wire to stop operation during cold weather or any time operation is not desired

The ELK-960 has proven to work trouble free for several years and the price reasonable at $30.
Click to expand...

Hey that sounds like a sweet setup, thanks! :clap:
 
I read all about the ELK-960 timer and it is difficult to set the timer minutes, trial and error and 'too' fine resolution of the dial. There were several versions/diagrams to wire up and none said that they actually worked. One even mentioned it started the fan on startup. No digital display of what is going on.

Just different ways to do the same thing.
 
CobraMarty said:
I read all about the ELK-960 timer and it is difficult to set the timer minutes, trial and error and 'too' fine resolution of the dial. There were several versions/diagrams to wire up and none said that they actually worked. One even mentioned it started the fan on startup. No digital display of what is going on.
Just different ways to do the same thing.
Click to expand...

 The ELK is a little touchy to set the minutes to an exact time but I have not found this to be a be a problem. I wanted two minutes, thirty seconds but couldn't get it less than three. That's fine for my usage. Adding more time is simple.
Didn't find it hard to wire. If the battery is disconnected, the timer will activate for one cycle when the battery is reconnected.

There is no digital display for the timer but I have no need as you can easily hear the fan, when it is running and the engine is off.
I had previously added a second fan relay, under the hood, for operating the fan when off-roading (or when sitting in summer traffic) and also added a dash LED light to show when the fan is on.
This same relay is activated by the timer. I added a diode to the timer's output wire (the one connected to the fan relay's coil) to prevent feedback.

The timer is mounted inside the console, at the front of the center storage bin. Getting to it requires removing a couple screws and pulling the bin's interior out.
http://www.flickr.com/photos/lwade/sets/72157617434915718/
Three and a half years and 45,000 miles later, it's still working fine.

 
Sounds good, I might play with that next.
 
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