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Location:
ACT
Registered:
May 2002
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 thermo fans
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Wed, 07 May 2003 00:30
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Is there any benefit in leaving the thermo fan running after the car has been turned off??
My thermo is hooked up to a temp sensor and runs until the temp drops even after the car is turned off.
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Location:
Lost in the K hole
Registered:
May 2002
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Re: thermo fans
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Wed, 07 May 2003 00:46
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unless youve got water flowing through the raditor, wtf is the point of having the fan running???
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Location:
ACT
Registered:
May 2002
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Re: thermo fans
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Wed, 07 May 2003 00:48
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i don't know , that's why i posted the question 
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Location:
Lost in the K hole
Registered:
May 2002
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Re: thermo fans
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Wed, 07 May 2003 00:50
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..... think about it
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Location:
ACT
Registered:
May 2002
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Re: thermo fans
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Wed, 07 May 2003 00:59
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ok so no water is running thru the radiator, so there's no point for the fan running.
my mechanic setup it up that way, so i thought there might have been a reason why he did it!
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Location:
Lost in the K hole
Registered:
May 2002
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Re: thermo fans
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Wed, 07 May 2003 01:12
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he probably shouldve wiried it into the ignition switched power so that when you killed the engine, the fan stopped.
the only thing that having the fans running with NO watr flowing would do - is move air around the engine bay. maybe you could do with this if youve got two spanking hot turbos in there, but then again, youd have a turbo timer which lets the engine over-run, as well as the fan continue...
if your fan runs on when the engines stopped, you should probably take it back and ask him to instal it properly.
cheers
ed
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Location:
ACT
Registered:
May 2002
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Re: thermo fans
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Wed, 07 May 2003 01:16
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Well then maybe i should leave it because i do have two hot stinkin turbos in there and i dont' have a turbo timer.
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Location:
Lost in the K hole
Registered:
May 2002
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Location:
Adelaide
Registered:
May 2002
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Re: thermo fans
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Wed, 07 May 2003 01:39
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does the water not still circulate due to the difference in heat and density of the water?
The stuff in the radiator will be cooler than that in the engine and hence more dense... It then sinks to the bottom of the radiator and then pushes water forom inside the engine up to the top of the radiator where it starts to sink again ie. circulates ?
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I supported Toymods
Location:
south of the big smoke
Registered:
May 2002
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Re: thermo fans
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Wed, 07 May 2003 01:42
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if im going to drive my car again in the next 5 minutes i leave my fans on as the heat soak on the 1ggte is pretty bad! so it takes a while to get efficent boast if the pipes get to hot
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Location:
ACT
Registered:
May 2002
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Re: thermo fans
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Wed, 07 May 2003 02:31
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Oz Craig
Is it just the fans or is the engine running as well?
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Location:
Brisbane
Registered:
May 2002
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Re: thermo fans
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Wed, 07 May 2003 03:55
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Ed: it's pretty normal for thermos to run after the engine is shut down, even on factory cars. Ever heard of heat soak? For example, my engine temperature goes pretty high after I shut it off, even though it was at "normal" temp when the engine was running (yes this is after letting it idle for 60 seconds or so). If my fans were hooked up to a thermostat instead of being hardwired to the ignition, this wouldn't happen.
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I supported Toymods
Location:
south of the big smoke
Registered:
May 2002
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Re: thermo fans
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Wed, 07 May 2003 04:14
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yeehaa i leave the car on for say a minute (turbo cooling) then however long i like with out the engine on, im gunna hook it up to my boot release button on my alarm to i can on/off it from that. i have twin 12" fans running so it keeps it pretty cool
norbie i thought only the 1ggte suffered from the realy bad heat soke
there ya go hey! u learn something new everyday
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Location:
ACT
Registered:
May 2002
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Re: thermo fans
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Wed, 07 May 2003 04:33
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Ozcraig-one of the reasons i brought this topic up is because it triggers my alarm when the fan goes off. The fan activates intermittently , so you don't really know when the bloody thing will turn off completely. I need to somehow wire the alarm so its independent of the fan.
Also i have 1 10" fan on 4 core radiator. I'm not sure whether its enough. Well nothings fried yet, so time will tell!
Therefore is a turbo timer needed?
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Location:
c'town, NSW
Registered:
May 2002
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Re: thermo fans
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Wed, 07 May 2003 04:56
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all engines turbo or N/A suffer from some heatsoak after shutdown, some manufacturers hook up their thermos to run after the engine has shut off (honda for one), but the effectiveness of this is another story all together (seeing as tho the water isnt moving, it may just be to keep new air moving into the bay.
my 1G only rises a few degrees after shutdown (id say 5 at most) so i am not bothered with it.
if your really worried about it do experiments with a temp probe or your temp guage after shutdown with and without the fans
an ideal situation would be to have the fan AND the water pump running for a while after shutdown, which could be done if you had an electric water pump.
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Location:
North Sydney
Registered:
May 2002
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Re: thermo fans
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Wed, 07 May 2003 04:58
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Just disable the voltage sensing on your alarm. Then it won't trip the alarm off. It's normal for the fans to keep running particularly on a 40+ deg day.
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Location:
Lost in the K hole
Registered:
May 2002
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Re: thermo fans
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Wed, 07 May 2003 05:43
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sure, like i said at the very top, letting the fans run will move a bit of air around the bay to help with heatsoak issues... BUT:
if the thermos are simply running off the thermatic switch in the bottom of the radiator, and are say switched to come on at 70deg or something, how long do you think the thermos are going to run on for before the temp of the water at the bottom of the radiator goes below 70deg??
the switching of the fans has sfa with the engine bay temp. having them run for say a standard period of 5 mins after shutting down the car might be a good idea, but i dont think that having them run on, and governed by the coolant temp, is a good way of doing it.
as i said before, if theres big engine temp and turbo temp issues after shutdown, get a turbotimer, and let the fans run on with it...
ed
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Location:
Montrose, VIC
Registered:
May 2002
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Re: thermo fans
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Wed, 07 May 2003 05:50
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There can be some benefit in leaving the fans on - thermal syphon will cause some water movement without a pump e.g. take off the belt, start the engine, after a while the rad WILL get hot.
Another thing - turbo timers... why? Much better to drive the car quietly for a minute or two before you turn it off, that way you'd likely have cooler everything anyway, plus it's one less temptation for some 13 year old to 'borrow' your car. Oh, and you can put the bloody thing in gear when you park it that way, rather than leaving all faith in the handbrake!
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Location:
sydney
Registered:
March 2003
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Re: thermo fans
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Wed, 07 May 2003 07:12
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While we are on the topic of thermo fans,
I have a 4ac engine, Would it do any harm if you leave the thermo fan on all the time without a thermatic switch. So as soon as you start the car the fan would spin until you turn it off. What do you guys think?
Thanks Dudes
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Location:
Sydney
Registered:
July 2002
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Re: thermo fans
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Wed, 07 May 2003 07:52
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My belief on thermo fans (installed on on my supra) is that if the car is off there needs to be water flow to get any result.
What happens if like my engine the water pipes on the engine are both at the top of the engine? If the water in the radiator is cold (after having thermo fans on for a while) and the actual engine is still hot, then CRACK! blown headgasket etc. I understand this is extreme, but technically it could happen.
Usually the thermometer that switches the fans is inside the engine, running the thermo fans outside the engine (radiator) won't cool down the engine where the thermometer sits. I could definately be wrong with this bit as I've no experience with leaving thermos on after the key (the key goes off everything goes off).
End of the day you must sit with your car for the required cool down time to cool down the turbos. Turbo timers are good, but it needs to be in neutral, and theives can get through turbo timers a lot quicker than through the key barrel. Also it is EASY to pickout a turbo car with one as the car is still on while the person walks away!
If you know your going to be stopping soon (2 streets away from home) then take it easy. Simple. When you get to your destination wait a little while and then turn it off.
Thermos with the key is fine DacBietAE86. I ran with this in my car for a few months. Then I connected up another relay to the computer and now it controlls the fans. Only thing you'll notice is that it might take a TINY bit longer to warm up.
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Location:
sydney
Registered:
March 2003
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Re: thermo fans
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Wed, 07 May 2003 08:41
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so let me make this clear,Having the thermo fan on all the time wont do any damage to the engine. Coz my dad was telling me it will cause problems, something about water flow or thermostat or something.
Just making sure hehe Thanks again HKSpete
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Location:
North Sydney
Registered:
May 2002
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Re: thermo fans
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Wed, 07 May 2003 08:59
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I don't see any problem with turbo timers if you set your turbo timer up correctly.
I just finished setting the turbo timer up on the weekend. I run a Jaycar turbo timer which i've made a few modifcations to and integrated it into the alarm.
The turbo timer cuts in when I take out my key, i then get out and arm the alarm, which activates the central locking, enables the internal ultrasonics, disables the starter motor and disables the fuel pump starting from the ignition.
Besides the fact the steering lock is now engaged and the shock sensors are still active as well it would be damn hard to attempt to steal the car. The alarm goes off as soon as you lift the door handle.
I love it cause there's an awesome corner 500m from my house and I can resist the temptation of some drift whilst i'm on the way home especially if its wet for some opposite lock drift! 
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Location:
Perth
Registered:
July 2002
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Re: thermo fans
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Wed, 07 May 2003 10:28
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| HKSPete wrote on Wed, 07 May 2003 15:52 |
My belief on thermo fans (installed on on my supra) is that if the car is off there needs to be water flow to get any result.
What happens if like my engine the water pipes on the engine are both at the top of the engine? If the water in the radiator is cold (after having thermo fans on for a while) and the actual engine is still hot, then CRACK! blown headgasket etc. I understand this is extreme, but technically it could happen.
Usually the thermometer that switches the fans is inside the engine, running the thermo fans outside the engine (radiator) won't cool down the engine where the thermometer sits. I could definately be wrong with this bit as I've no experience with leaving thermos on after the key (the key goes off everything goes off).
End of the day you must sit with your car for the required cool down time to cool down the turbos. Turbo timers are good, but it needs to be in neutral, and theives can get through turbo timers a lot quicker than through the key barrel. Also it is EASY to pickout a turbo car with one as the car is still on while the person walks away!
If you know your going to be stopping soon (2 streets away from home) then take it easy. Simple. When you get to your destination wait a little while and then turn it off.
Thermos with the key is fine DacBietAE86. I ran with this in my car for a few months. Then I connected up another relay to the computer and now it controlls the fans. Only thing you'll notice is that it might take a TINY bit longer to warm up.
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Convection causes hotter coolant to flow to where there is cooler coolant. The engine is a big heat sink and keeps heating the coolant for some time after stopping the engine. This keeps happening until the thermostat closes.
You can't get thermal shock in this situation.
The thermo fan temp sensors are almost always located in the radiator.
Circulating air around the engine when stopped is pretty useful, particularly after a few laps of the track.
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Location:
Sydney
Registered:
July 2002
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Re: thermo fans
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Wed, 07 May 2003 14:25
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| Blown86 wrote on Wed, 07 May 2003 20:28 |
Convection causes hotter coolant to flow to where there is cooler coolant. The engine is a big heat sink and keeps heating the coolant for some time after stopping the engine. This keeps happening until the thermostat closes.
You can't get thermal shock in this situation.
The thermo fan temp sensors are almost always located in the radiator.
Circulating air around the engine when stopped is pretty useful, particularly after a few laps of the track.
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I'm not up on the Convection theory sorry, but in chemistry we were taught that hot water would rise and cold water would drop. The cold water can't drop on my car as it has no where to go because the hose goes to the top of the engine, not the bottom.
My thermo fan sensors are located in the pipe on top of the engine, they're controlled by the computer and set to turn on at 92 degrees, off at 86 (thermostat is at 86). I'm going to raise the turn off to 87 as it never turns off at the moment.
I've never seen a *factory* sensor located in the radiator. Granted they could have it, I've never seen it though.
If your at the track you don't turn your engine off as soon as you come in! You let it idle for more time than a turbo timer to make sure everything levels out before turning it off.
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Location:
Sydney
Registered:
July 2002
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Re: thermo fans
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Wed, 07 May 2003 14:29
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On the trip to nowra that a few Toymodders went to. We stopped down at our destination and I think it was Craig that was standing next to my door, and could feel the hot air from the engine bay warming up his feet.
Thermo fans sure can pump some air. Pity the mk3 supra bays aren't the best for under bonnet temps and extracting air. 'specially with a wider than standard engine in it!
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Location:
Hobart, Tas
Registered:
May 2002
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Re: thermo fans
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Wed, 07 May 2003 14:44
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| DacBietAE86 wrote on Wed, 07 May 2003 17:12 |
While we are on the topic of thermo fans,
I have a 4ac engine, Would it do any harm if you leave the thermo fan on all the time without a thermatic switch. So as soon as you start the car the fan would spin until you turn it off. What do you guys think?
Thanks Dudes
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Umm... why do you want to do this??!! I'm converting my mech fans to elec, and one of the benefits is that the electric fan will only be on when it needs to be. This means the engine will warm up more quickly (A Good Thing i belive), and the fan is only using power when it has to be on. The problem with mech fans is that they are on all the time (even clutched ones), whether they need to be or not. If I wired the elec fan to be on all the time, there would be more power losses than the mech fan in the first place.
I think if you needed your fans to be on all the time - liek you were somehwere really hot - the thermatic switch would have them on all the time anyway
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Location:
c'town, NSW
Registered:
May 2002
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Re: thermo fans
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Wed, 07 May 2003 22:13
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also having the elec fan on all the time greatly reduces the life of the fan..
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