The Ace

This is my problem: I have never heard the stock e-fan come on after I shut down the car. I know that the stock fan is belt-driven, so it cannt work after the car is off. Also I know that almost all cars activate their fans when hot to cool engine down after you shut them down (because they have e-fans).

Now my question is this: is my thermoswitch bad, or does the stock e-fan come on only when turning on the A/C ? I mean, if the e-fan never comes on, this means I'm leaving the car boil in its own heat...

Scott 89t2

no car turns the fans on with the car is off....


the e-fan on the front should come on when the A/C is on. or as an emergancy fan when temps get too hot. I think it turns on around 210F or so.

The Ace

Almost every car I have owned and know can turn the fans on after you shut it down to cool the engine

Aha, thats what I was looking for. I know it comes on with the A/C (as per FSM), but I was thinking it should also come on through the thermosensor...if this is normal behaviour, then why it didnt come on when I overheated a couple of times last month ?

hypntyz7

IT wll come on at a high temp, around 2/3 on the stock gage. OR, if you unplug the thermosensor plug, it will run constantly.

christi

Well, I do know on 1st gens, the stock e-fan turns on for quite sometime....

1_dollar_83_RX7

will a bad thermostat sensor cause coolant to be pumped into the overflow tank, just like water seal damage would?

HAILERS

The fan should come on at 97C or 207F, whichever comes first. humor

If you have a overheating problem its gonna take more than that little fan to fix it. I'd be looking at all the more common items as, radiator cap, broke hose b/t the filler and the overflow tank, thermostat, and the real dark thoughts like internal seals of the engine.

There's a free download of the cooling system on http://fc3s.org

Running cool in Texas. Gotta run now. Need to execute another criminal down in Huntsville to make bed space for the new guys.

NZConvertible

I've never seen any car run it's stock electric fan after you turn it off. Not ever. Doing so is pointless because there's no coolant flow, so all you're cooling is the coolant in the radiator. The car won't "boil in it's own heat." The engine is off, there's no more heat being generated, so there's physically no way it can get any hotter. It can only cool down. Also, if this was necessary, Mazda would have fitted electric fans to all FC's, but they didn't.

jimmyv13

My Accord's e-fan ran after I shut it off.

Jodoolin

Here is a thought. The thermodynamic experts may want to respond.

I have a friend with an add on aftermarket e fan in front of the radiator on his motor home. It has a temp sensor attached to the outer grill of the H20 radiator. It runs when the preset temp is reached whether or not the engine is actually running. Both of us have observered it kicking on in cycles after the motor home has been shut down. It may actually cycle 4 - 5 times over a one-half to one hour period after the engine has been shut off. It may be off 5 - 10 minutes then cycle on again.

This is the logic we used to explain the intermittent cycling after the enginer is shut off.

1. The e fan cools the water in the radiator

2. This creates a cooler thus denser and heavier water in the radiator.

3. The heavier water displaces the hoter (lighter) water at the bottom of the radiator thus creating a thermal circulation which displaces the hoter thus lighter water distal to the radiator throug the engine.

4. This occurs rather slowly but results in hot water returning to the radiator which trips the e fan to cycle on again.

If this basic thermodynamic is in fact occuring then it occurs in all water cooled internal combustion engines (with open thermostat).. no?

Like many of you, I have indeed seen/heard e fans cycle on after an engine has been rurned off and it does not occur immediately after the shut down.

Not sure I made the point exactly as I intended.. Got my drift?

HAILERS

Sort of a correction on my above post. The figures are right and come from the pages mentioned in the fsm. But I did not mean to imply that the fan comes on with the car off. Frankly, I don't know one way or the other. The one that was on my turboii got transfered to my n/a and is wired just to turn on when the a/c is turned on. Sometime I'll put it back on the tii and see what happens. I don't remember it ever coming on with the key off and hot. Some cars do, do that(non rx), for sure.

Tom93R1

iTrader: (2)

I know Hondas will cycle their fans after being shut off, but I have never seen any other car do that. My 87TII didnt do it and my 93 doesn't do it. After shutting down your engine the coolant will heat up. When I shut my car down at 95C for about 15 minutes the water temp will get up to around 115C. My guess is that the cooling system takes heat away from the engine but it is not 100% efficient. Just like water leaving the radiator is not cooled all the way down to ambient temp, the coolant leaving the engine is not heated all the way to the engine temp. When the water sits after shutting the car down it is slowly heated all the way to the engine temp.

briandinda

Once, a long time ago, in a galaxy far, far away....I owned a Ford Fiesta.....<please keep laughter to a minimum>....I found an after-market catalog and in it was a kit you could buy to by-pass the ignition and allow the e-fan to run independently. After I installed it...<it ended up being a couple of wires and a connector> my fan did run intermittently on hot days once I'd parked. The kit was sold as a way to help perserve the engine. There should be a way to do the same on the RX's.....was thinking of trying it on my '87. Can't see why having this extra cooling would hurt anything except to drain a bit of juice off the battery.

NZConvertible

The process you describe above is called thermosiphon, and does indeed happen in all cooling systems. In fact, in the very early days of automobiles, engines didn't even have pumps and relied entirely on thermosiphon to move coolant around. As power outputs grew, pumps were added so the cooling system could keep up.
However I'm sure this is not the only thing causing the fan to cycle in your situation, and probably not the main reason. Like I mentioned above, no heat is being added to the system, it's only leaving it, so there probably would be enough temperature difference to induce much thermosiphon. But what was happening was heat moving around in the engine due to conduction. Some parts of the engine run much hotter than others, so when the engine is stopped these hotter and cooler spots attempt to equalise. Basic thermodynamics. So heat is moving from the hot spots and eventually making its way to the radiator, triggering the fan. I think there's a bit more to it though, because cycling the fan severla times is really weird!

Jodoolin

Jason.. many thanks for the affirmation. I have been respecting your opinions and am now certain you are of even greater intellect since you agree with my observation. (he grins as he types by the way)

The Ace

Just to reassure anyone here, and especially NZ: I know for a fact that all Hondas can turn on their fans (two if they have AC) after shutting down the engine in order to remove the remaining heat from the engine bay. I also know that VW cars do that as well (at least my dad's Passat, all Golfs that I know, and also some Jettas that I have seen).

Also, I know that no more heat is generated when shutting down the engine, but there sure is a shitload of it already in the engine bay Stopping the car (no air flow from movement), and stopping the fan (no air flow PERIOD) means that all this heat stays in the engine bay. For the first couple of minutes (heat transfer is NOT instantaneous) the engine is at its high operating temps WITHOUT the air flow from the car's movement or the fan(s). That could sure mean trouble, couldnt it ?

And the fans are not just cooling the coolant in the radiator, they are also trying to cool the engine itself, or the engine bay in general, by providing the air flow necessary to remove as much heat as possible...the same can be achieved (I guess...) by opening the hood, but this is of course a very mediocre solution....

What I'm wondering is why Honda and VW (and I'm sure BMW and Mercedes) have provided such systems in their cars, and Mazda didnt (especially in the turbo-ed wankel powered cars, i.e TII and FDs), which need them the most....

NZConvertible

I think the fact that most automakers (including BWM and M-B) don't do this indicates it's probably not as important as you might think. And I doubt many would be happy running such a high-drain component without the alternator charging the battery.