Options for keeping Thermo fan running when engine stopped

[1200det]

Im after some ideas of how i can keep a thermo fan running for something like a few minutes once then engine has been switched off ?

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[mike1980ra40]

Off the top of my head, an override switch that turns on a timer, or a timer is hooked
up to the ignition were there is constant power when ignition is off. timer kits you could
probably get from jaycar.

[CrUZida]

What controls the thermo now?

Mine is controlled by a Tridon switch, and the relay is powered directly from the battery, so even after the car is turned off the thermo still operates.

On a hot day it can run 2-3 more times after I have turned the car off (on for a minute, off for 3, on for 30 sec, off for 3, etc etc)

[oldcorollas]

turbo timer could do it.

although is ther emuch point when the coolant in the engine will not be circulating?
maybe fan combined with EWP for a few minutes would be a good thing?

[1200det]

Well now the vehicle has the standard thermo and switch and im looking at using another Thermo fan and wanting it to run when the vehicle is switched off or even run the both when the engine is off

Cruzida - Exactly what im after whats the details on the Tridon switchs

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[CrUZida]

Check the FAQ

[1200det]

Im having a issue where once the vehicle is turned off its blowing off the Radiator cap and bubbling the overflow. Vehicle doesnt get HOT nor open the Rad cap when running only after switching it off.

Recoed Radiator and New top/bottom tanks
New 1.3 Bar Radiator Cap
Completely flushed and using minimal coolant and burped several times

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[YLD-16L]

Damo here is the cattldog in this link as provided by CrUZida

http://www.toymods.net/forums/showthread.php?t=5125

[off-road]

I would rig up a temporary wire from the fan to the battery first to make sure running the fan with the engine off is going to fix the problem.
Because the water is not being circulated cooling the radiater will not have any effect because Isuspect the problem is caused by water in the motor being heated and expanded as it absorbs heat from the metal.
If you have a overflow bottle and a recovery cap it may not be that bigger deal anyway.
Also if you don't have a recovery cap maybe the radiater is too full.

[mike1980ra40]

something else you could add to the turbo timer (mentioned above) is an electric booster
pump that runs with the fan when the engine is off. i think davies craig make them.

edit: found a link to it.

http://www.daviescraig.com.au/main/display.asp?pid=27

[Muzza]

I have temp switch through a relay and i used a driect battery supply so therfore when the switch closes the fan still runs when the engine is off,

[mike1980ra40]

if you put a booster pump in parallel to that the coolant is still being circulated

[1200det]

Would you be able to circulate the coolant when the Thermostat is closed , I wouldnt think so

[mike1980ra40]

Not when thermo is closed. while it's still open it will, thats why I think if the pump was
running off a timer/and thermo switch combination then the pump will switch off with the fan.

[RobertoX]

if its that hot that its bubbling out the overflow the thermostat will probably be open anyway.

There may still be some circulation of coolant without the pump running due to convection (cooler water in radiator and hotter in engine), whether it is enough is another thing though. If you kept the thermofan running after it is shut down it may just be enough to give some circulation by cooling the radiator coolant a little more and prevent the boiling thats due to stationary coolant.

I would rig up a temporary wire from the fan to the battery first to make sure running the fan with the engine off is going to fix the problem.

It cant hurt to try this and if it doesn't work you could move onto bigger things such as an ewp, if it does work make it permenant using whatever method you want (temp switch, timer etc) and be happy. Is the problem reproducable enough to experiment a bit?

[Cuzzo]

When the thermo is closed, doesnt the water still flow around half the system? Im saying this because the water pump runs all the time.

[love ke70]

umm, first up. how longs it been doing this for?
my car does this if the rad is over full. it finds a happy balance after a few days and have no more issues.

that is unless i give it a caining and switch it straight off.
have you thought giving it a minute or 2 to drop temps, even if water temp doesnt drop the engine bay and component temps prob will.

surprised no one has mentioned that before.

this is particularly relevant if its a turbo motor...

[MRMOPARMAN]

actually due to natural convection? the water in your cooling system does circulate, just very slowly. some cars (eg mitsubishi colt) run fans after turn off from the factory.

thats also the way vintage cars etc used to run without radiators.
so yes it is worthwhile running the fan after turn off.
ill also add an interior light delay, connected up to a relay would also do the job.
tridon switch sounds better though.

when the thermostats closed the water still circulates from the block to the head and back round again.

[ma61turbo]

I'm running the same setup as Cruz and a few others. Tridon temp switch and thermo fans powered directly from the battery. There is enough convection in the system for the fan to turn back on once or twice after it turns off the first time.

Personally I prefer this method than powering the fan from another source that gets power only when the engine is on. It helps the engine cool down better once stopped and is very, very good at stopping heat soak.

I've been told that it shouldn't be done this way, as it can lead to a cracked head but I personally call BS on this. After all, the fans will only cool the system to whatever their lower threshold is, and there is far too much natural convection(and probably still some water movement too) for it to just cool the water in the rad and not in the motor.

[ma61turbo]

Im having a issue where once the vehicle is turned off its blowing off the Radiator cap and bubbling the overflow. Vehicle doesnt get HOT nor open the Rad cap when running only after switching it off.

Recoed Radiator and New top/bottom tanks
New 1.3 Bar Radiator Cap
Completely flushed and using minimal coolant and burped several times

.

Any idea what temp the switch is? I would guess that it is a bit on the hot side and as such when you turn the motor off, and the fans turns off, all the heat still in the block causes the system to cook pretty quickly.

Whatever temp your thermostat is, I'd suggest having a switch that turns off at least 3 degrees above that. So, if your thermostat is an 85, use a 90-95 switch. If you have an 82 deg thermostat like I have, run a 85-90 switch. I've played around with a number of combinations of thermostat temps and thermoswitches and this seems to give the best results.

Add to that power from the battery and you'll be laughing.