4AGE: question about side vent

[Mr.Baca]

so i have my first mr2 and its just parked in my driveway because my license is suspended so i cant move it well i turn on my car every 3 days and let it warm up till the thermostat is half way but my side vent fan never turns on is that normal does it only turn on when it is realy hot like when driving for a while

[curvesrgood]

I don't hear mine kick on very often... I'm guessing the car does have to be pretty hot before it kicks in. I've noticed a few times in the past few weeks that if I've driven the car very hard and bring it home to park it I hear the fan running. Otherwise I don't think I ever hear it kick on. Anybody else?

[muffinman]

the vent fan has an engine bay sensor and has nothing to do with coolant temp. i have never seen mine come on by itself. if you want to test it just unplug the sensor (big white plug at rear of head ) with the car running and it should kick right on.

[mr2_jake]

Mine comes on quite frequently, but only for a few seconds. If I remember correctly, when the engine bay temp reaches somewhere around 120 it kicks on till it lowers to around 100, then shuts back off.

[toyotaspeed90]

Key just needs to be set to "on" for it to turn on.

when I had my 7age in my 87 I heard it kick on all the time.... I had an unshielded header, though.

[YellowJacket]

Originally Posted by toyotaspeed90

Key just needs to be set to "on" for it to turn on.

when I had my 7age in my 87 I heard it kick on all the time.... I had an unshielded header, though.

Not true. This fan is triggered by a sensor in the engine bay when the ambient temperature reaches 168 degrees for more than 10 minutes I believe, and it is controlled by a fan computer behind the ecu in the trunk. If your fan is on all the time, you need to replace your fan computer. It is bad. When you turn you car on the engine fan should NOT come on if everything is working properly. If it does come on, then its in failsafe mode from a failed component, most likely the fan computer.

As mentioned you can pull the wire from the sensor in the engine bay to test the system. If it doesnt turn on after you unplug it, you have another problem and can test the fan itself by running 12v to it to confirm the fan itself turns and wiring works there.

If it does turn on when you unplug the fan wire from your sensor but doesnt turn on after Sitting idle for a while after a very spirited drive then you either have a relay, sensor (not as likely), or a fan computer malfunction (very likely). The sensor is testable with an ohm meter and some hot water but like I said its the least likely to fail in my opinion. The fan computer failing is probably the main cause of fail-safe (always on with ignition).

The fan is not loud, but you can hear it, and it draws a good amount of air (and dust) from outside to inside, so you should definitely be able to tell its on audibly if you are listening for it and by the feel of the air induction with your hand or hold a piece of paper against it and it will suck it to the car... cigarette would work if you smoke.

The haynes manual or BGB states all this a bit more eloquently, but thats the deal paraphrased.

side note: The cooling fan dummy light in the dash is ONLY for this fan. It lights up when the fan SHOULD trigger on but does not. It has nothing to do with the liquid cooling system.

[mr2_jake]

Hmm, mine comes on when key is in "on" position. I usually run my 2 hard on the curvy race track I call my driveway, and when I park and shut her down the fan remains on, regardless of key position, for a few seconds.

[toyotaspeed90]

Originally Posted by YellowJacket

Not true. This fan is triggered by a sensor in the engine bay when the ambient temperature reaches 168 degrees for more than 10 minutes I believe, and it is controlled by a fan computer behind the ecu in the trunk. If your fan is on all the time, you need to replace your fan computer. It is bad. When you turn you car on the engine fan should NOT come on if everything is working properly. If it does come on, then its in failsafe mode from a failed component, most likely the fan computer.

As mentioned you can pull the wire from the sensor in the engine bay to test the system. If it doesnt turn on after you unplug it, you have another problem and can test the fan itself by running 12v to it to confirm the fan itself turns and wiring works there.

If it does turn on when you unplug the fan wire from your sensor but doesnt turn on after Sitting idle for a while after a very spirited drive then you either have a relay, sensor (not as likely), or a fan computer malfunction (very likely). The sensor is testable with an ohm meter and some hot water but like I said its the least likely to fail in my opinion. The fan computer failing is probably the main cause of fail-safe (always on with ignition).

The fan is not loud, but you can hear it, and it draws a good amount of air (and dust) from outside to inside, so you should definitely be able to tell its on audibly if you are listening for it and by the feel of the air induction with your hand or hold a piece of paper against it and it will suck it to the car... cigarette would work if you smoke.

The haynes manual or BGB states all this a bit more eloquently, but thats the deal paraphrased.

side note: The cooling fan dummy light in the dash is ONLY for this fan. It lights up when the fan SHOULD trigger on but does not. It has nothing to do with the liquid cooling system.

the relay is turned on by the COR...... which turns on when the key is set to on, not necessarily when the engine is running. It turns on when the temp reaches where it should.

the sensor is not a switch style sensor.... strangely enough, even though the technology was there for a switch style thermistors, this one isn't.... it's a true thermistor (I know this because I had to use one as an intake sensor on a JDM gze). Also, I doubt there's a timer built in as there's no need for one.

so, if you had read what I said correctly.... it can turn on when the key is set to on... I did NOT mention engine bay temp.


Further, if you all want to go on about this.... there is little that the side vent does at above 35mph..... aerodynamics of the car make it somewhat useless.... the lower plastic covers (and the vents in the engine lid) are meant for air movement to go from under the car to up through the engine bay. So, for anyone wanting to add a fan to the engine lid for whatever reason, wire it as a puller.

[YellowJacket]

Originally Posted by toyotaspeed90

the relay is turned on by the COR...... which turns on when the key is set to on, not necessarily when the engine is running. It turns on when the temp reaches where it should.

the sensor is not a switch style sensor.... strangely enough, even though the technology was there for a switch style thermistors, this one isn't.... it's a true thermistor (I know this because I had to use one as an intake sensor on a JDM gze). Also, I doubt there's a timer built in as there's no need for one.

so, if you had read what I said correctly.... it can turn on when the key is set to on... I did NOT mention engine bay temp.


Further, if you all want to go on about this.... there is little that the side vent does at above 35mph..... aerodynamics of the car make it somewhat useless.... the lower plastic covers (and the vents in the engine lid) are meant for air movement to go from under the car to up through the engine bay. So, for anyone wanting to add a fan to the engine lid for whatever reason, wire it as a puller.

Yeah, I get the whole useless above 35mph thing.. worth mentioning though... I always thought that was a cooling fan more for if you are sitting in slow traffic or at idle on a hot day anyway... I wouldnt imagine it would ever get over 158 above 35 mph in the engine bay anyway with the airflow there.

and Yeah, I understand now what you are saying when you mean it will "turn on." I was interpreting you to mean all you have to do is turn your key on, and the fan runs (all the time). Which is a failsafe situation. But it sounds like you mean, the circuit is on.

I couldnt remember about the accuracy of my "timer" statement, and took a quick look at a BGB and all it says is that the fan comes on for a sec during ignition (as you indicated) but immediately shuts off if the sensor reads under 129 degrees and turns on if its reading over 158 (not 168) degrees.

As far as the timer part, the BGB doesnt state anything that I found easily, but I recall getting that info (right or wrong) from another forum (dont believe everything you read right) and as the cooling fan computer behind the ecu is what monitors the sensor/thermistor... could it not act as the "timer" and not trigger the fan on unless it gets a constant reading for a specific duration?

Makes me want to have some extra status indicator lights... rad fan , engine fan , and tvis.

[toyotaspeed90]

yes.....

on track days, if the side vent fan is on I will turn the engine off but keep the fan running and the engine lid open when in the pits.

[YellowJacket]

Originally Posted by toyotaspeed90

yes.....

on track days, if the side vent fan is on I will turn the engine off but keep the fan running and the engine lid open when in the pits.

Which is accomplished by turning the key to accessory position to kill the engine but keep the circuit open so the fan runs, correct? Pretty cool. (literally)

[toyotaspeed90]

yes.... typically (again, at the time it was a running rich 7a on a header w/o shields... aka gets hot there) it would run for about 3 min and shut off.

[YellowJacket]

Originally Posted by toyotaspeed90

yes.... typically (again, at the time it was a running rich 7a on a header w/o shields... aka gets hot there) it would run for about 3 min and shut off.

But is the fan really necessary or effective or just helpful in that situation?

I wonder how long it would have taken for the engine to cool on its own to the same 128 degrees needed to turn the fan off....

and then the second question, is, in the scenario where the engine does take X minutes longer to cool down on its own to 128, does it really matter that the engine took X more minutes to reach the same 128 degrees?

I still surmise the side vent fan becomes the most effective and useful at long idle or in slow traffic jams on the interstate in the sweltering heat...

[scottohno]

Originally Posted by YellowJacket

But is the fan really necessary or effective or just helpful in that situation?

im guessing just helpful to prevent warpage.

I wonder how long it would have taken for the engine to cool on its own to the same 128 degrees needed to turn the fan off....

and then the second question, is, in the scenario where the engine does take X minutes longer to cool down on its own to 128, does it really matter that the engine took X more minutes to reach the same 128 degrees?
actually wouldnt it benifit if it cooled down slower to prevent the metal getting hardened in a way.

I still surmise the side vent fan becomes the most effective and useful at long idle or in slow traffic jams on the interstate in the sweltering heat...

well my car still overheated going 135mph (yeah on stock everything) when the airflow through the radiator was blocked by the front license plate. i think anything below 30-35 mph and the side vent cools the engine enough for the radiator to work less, and when going over 35 you have enough air going through the radiator to cool the engine internally.(unless you have a sheet of metal in front of it that says illinois) plus at higher speeds all the heat is inside the engine, and thats what were worried about. ambient air helps, but only so much. not like its an air cooled beetle from the 50's

[YellowJacket]

Your engine overheating was due to exactly that - the engine overheating. How much the license plate contributed is just conjecture.

It wasnt the ambient temperature of the engine bay that had anything to do with your overheating and that is where the sensor is that the cooling fan computer uses.

You will likely never hear the engine bay fan come on over 10 mph in my opinion. You simply have enough or equal air movement in comparison to what the fan can produce that you wont get to 160 degrees..... Except for extreme situations like after you have gone on a heavy flogging of your car and then come to a complete stop. Or maybe sweltering summers in stopped traffic (i.e. traffic light).

There is simply equal or more movement of air in the engine bay caused by motion of the car and as most agree more air is moving under the bottom of the car up through the engine bay to the top (not down) and that air is more than the fan can produce and therefore the ambient temp in the engine bay is regulated to lower than 160 by that "ram air" and not the fan.

Most certainly your fan was no help nor hindrance to your overheating at 135mph. I suspect you simply pushed an old car past its abilities in its condition.

[scottohno]

i moved the license plate over to the left side of the bumper. no more overheating.

and no damage to HG or head WOOOOOOO!

it was mounted in front of the grille and i also have 2 fog lights in there of considerable size. the rectangle ones. so all in all the grille ws blocked and revving to 6000 with the radiator blocked is what probably caused it.

i cant get it to overheat now that i removed the plate, and the lights are soon to go.

[YellowJacket]

If you had that large of an effect by moving the plate, then your radiator/cooling system is already severely restricted due to some other reason and that must have put it over the edge. Are the fins all bent up? Has it been really flushed well? Do you have lots of debris and dirt in the fins? The mk1 has a really robust cooling system ... its been called overkill more than once.

So you likely have something else going on... tstat oem? and functioning properly? Worn or cavitating water pump? Air in the system? etc etc

[scottohno]

Originally Posted by YellowJacket

If you had that large of an effect by moving the plate, then your radiator/cooling system is already severely restricted due to some other reason and that must have put it over the edge. Are the fins all bent up? dont think so Has it been really flushed well? not in the year ive owned it, not yet anyway, so no Do you have lots of debris and dirt in the fins?probably The mk1 has a really robust cooling system ... its been called overkill more than once. mhmmm lots of coolant

So you likely have something else going on... tstat oem?prolly not, but ya never know... i havent replaced it yet and functioning properly? eh its ok. keeps it cool and gets me heat eventually Worn or cavitating water pump? im sure it does Air in the system? prolly from the water pump etc etc

im a very "aint broke dont fix it" kinda guys. im getting to it. my 2 was 1100 dollars wen i got it. i got it about a year ago. (a year on the 23rd) and it hasnt given me too much trouble other than an alternator. if it starts leaking coolant, ill look into it. right now im taking care of an oil leak problem. got the parts, getting done this weekend or monday/tuesday latest. motor mounts too. it has 220k and sat for about 3 years. how do i know this? 100 miles on the tires and they all blew out at the same time at 100 mph. fun day.

i have a lot of things to do and if the cooling system keeps the car cool unless im doing 135 ill do 120 on my way to school, no biggie. i will get a tstat soon and a water pump and prolly an oil pump too. but i need to get time to work on it. i have 5 vehicles and im 18 years old and the newest vehicle is a 94. my other 4 cars are trucks, and theyve all got their own little things wrong. i go to college 8hrs a day 5 days a week, and i have to see my girlfriend sometime. so when i say ill get to it, i mean to say ill get to it when it causes a problem thats an everyday problem, not when i do specifically 135mph in hot weather in the middle of indiana.

[YellowJacket]

Dude, if you are serious about your driving habits, then don't worry about fixing anything. You are not going to live long enough for any of it to matter.

Seriously, take a step back and take a look at yourself. 18 makes you still stupid and not immortal. I know because I was 18 once too. Why are you putting your life in the hands of a neglected 25 year old car you just got?

Seriously. Either you have been extremely lucky to this point, or you are a pathological liar.

[scottohno]

Originally Posted by YellowJacket

Dude, if you are serious about your driving habits, then don't worry about fixing anything. You are not going to live long enough for any of it to matter.

Seriously, take a step back and take a look at yourself. 18 makes you still stupid and not immortal. I know because I was 18 once too. Why are you putting your life in the hands of a neglected 25 year old car you just got?

Seriously. Either you have been extremely lucky to this point, or you are a pathological liar.

luck i guess.

that and wen i get out of school nobodys on the southbound side of the highway. i culd just go and its straight with minimal curves. highways here are gentile except for the construction/potholes but they just replaced a bunch so thats where i do it.

wel did. til about the middle of november wen i moved. now the northbound traffic is the speed limit enforcer, so i dont.