Radiator Fan - Car Noob 101

[Euro7R]

These cars take forever to cool down; however, in regards to the radiator fan.

The radiator fan kicks in and spins when the a/c is turned on. When the a/c is off, the radiator fans don't spin. In what other circumstances does the radiator fan starts spinning? If the a/c is never used, the radiator fans never turn on? How does the engine cool itself?

Car noob 101.

Thanks.

[Ultramaroon]

After driving the car for 10-15 minutes, park it, leave the engine running and pop the hood.

Anywhere between immediately and a few minutes, one of the fans should start cycling on and off.

[extrashaky]

Originally Posted by Euro7R

The radiator fan kicks in and spins when the a/c is turned on. When the a/c is off, the radiator fans don't spin. In what other circumstances does the radiator fan starts spinning? If the a/c is never used, the radiator fans never turn on? How does the engine cool itself?

It comes on again when the coolant temp hits a certain level, and it's higher than you would expect. On mine, it lets the coolant temp get up to around 210° before it kicks on again. When the A/C is on, I usually run between 190° and 195°.

The temp gauge on the dash will show the needle in the same place either way, because it's not really a temp gauge. It's merely an indicator that acts like a temp gauge. When the car is warming up, the needle will be below the "normal" line. Once it gets to the normal line, it will stay in that same spot as long as the temp is within the "normal" range, which apparently varies as much as 25°. It doesn't move above that line until you start overheating. It's basically an idiot light made to look like a gauge.

I hate idiot lights (or in this instance, an idiot gauge), so I run Torque and monitor the coolant temp as one of my Torque gauges. I had been running the A/C all last summer and was used to seeing my temp around 190°. On the first cool day in the fall, I turned it off and saw my coolant temp shoot up to 210°. I thought something was wrong with the car and took it in for service. Everything tested fine.

A 20° swing in coolant temp seems nuts to me, but apparently that's normal behavior for this car. If you're playing the That's Normal drinking game, time to drink up. I did note also that the oil temp seems unaffected by that swing in coolant temp, so it doesn't seem to be cooking the motor. So I suppose you can trust the idiot gauge to do its job, and as long as it's showing normal, not worry about it.

[Doanation14]

You don't always need the fans to cool the coolant. your vehicle's velocity in most cases will provide enough airflow to the rad for it to keep the coolant in its operating temp. your car's thermostat will start to open around 90-95 C (194-203 F) and allow coolant to flow through the rad only when it reaches that temp. The fan logic is controlled by a few different factors, AC operation being one of them. Since the condenser is in front of the radiator you may need more airflow then normal to achieve the same amount of coolant cooling because of the extra AC load.

[extrashaky]

Originally Posted by Doanation14

You don't always need the fans to cool the coolant. your vehicle's velocity in most cases will provide enough airflow to the rad for it to keep the coolant in its operating temp.

That doesn't help you in traffic. In the incident I described above, the temp stayed below 195° as long as I was moving and would then start climbing as soon as I stopped at a red light. It behaved exactly like my Cherokee did when its viscous fan clutch went out, except that these cars don't have a viscous fan clutch, which had me thoroughly confused.

Originally Posted by Doanation14

your car's thermostat will start to open around 90-95 C (194-203 F) and allow coolant to flow through the rad only when it reaches that temp.

Those numbers are a little high. The FSM lists the normal opening range as 187° to 194°F (86° to 90°C). It will be fully open at 195° unless it's defective.

[Ultramaroon]

Uggh. I had no idea that the temp gauge was a liar. All this time I thought the temp control was rock solid.

First a waste of real estate for a worthless redundant speedo and now this? I'm seriously disappointed.

[Haeb]

We recently had a Subaru (Forester, not BRZ) that had a malfunctioning gauge.. it was supposed to remain mostly in the middle of the gauge until temps went beyond 220deg then it would climb. At 250deg it should have been at the top of the range, but this gauge was hitting the overheat mark at around 210-215. We changed sending units, and drove it, changed the gauge and drove it, still had the same symptom...point of all this is while I was driving the car in the California summer heat with the a/c on the temps on the scanner would swing wildly...anywhere from 190 to 225+...all of which was perfectly normal. After we added a resistor to the wire feeding the gauge, it remained constant in the middle through a more or less 40deg temp swing.

[strat61caster]

Originally Posted by Ultramaroon

Uggh. I had no idea that the temp gauge was a liar. All this time I thought the temp control was rock solid.

First a waste of real estate for a worthless redundant speedo and now this? I'm seriously disappointed.

Yeah it sucks that it's not accurate but from what I've seen reports are that the cooling system is rock steady even under heavy track conditions.

Edit: Not accounting for oil temps that is.

[go_a_way1]

Is there a way to have the fans kick on sooner??

[Tcoat]

Originally Posted by go_a_way1

Is there a way to have the fans kick on sooner??

Why? To what advantage?

[go_a_way1]

Originally Posted by Tcoat

Why? To what advantage?

My hope would be to keep oil/coolent temps down a little in traffic. Now I think about it, it seems kinda pointless haha!!

[Tcoat]

Originally Posted by go_a_way1

My hope would be to keep oil/coolent temps down a little in traffic. Now I think about it, it seems kinda pointless haha!!

Ya, it is designed to keep everything where it is supposed to be as is. Olden days when the fans were powered by a pulley we had overheat issues when idling in traffic but that doesn't seem to be much of a problem anymore.

[extrashaky]

Originally Posted by Ultramaroon

Uggh. I had no idea that the temp gauge was a liar. All this time I thought the temp control was rock solid.

I was watching the gauge when I went out to lunch and comparing it to my reading in Torque. The dash gauge hit the middle at 180° and stayed there. I know from my prior experience that it stays there at least to 210°. I don't know how much higher you have to go before the needle moves off normal. I suspect there's a point at which it jumps up above normal without showing as overheating, then another threshold where you get a warning light, so that you get some kind of indication that your system needs attention before you reach a dangerous temp.

I do understand why they've done this. Most newer cars have this same type of "gauge." Most cars also have a range of temps that are considered normal rather than a single expected running temp, and the actual coolant temp can change depending on a number of different factors. In the past some people would see their temp gauge showing a little hotter than usual and think it needed service when it didn't. At the same time, if you take away the temperature gauge altogether and just provide an idiot light, you don't give the driver any indication of when the motor is still warming up or when it's above the normal range but not quite overheating yet. And I think people like seeing a gauge and imagining they know what it's telling them. People tend not to trust idiot lights.

So you get a weird hybrid of a gauge and idiot light to keep certain drivers from freaking out about the car running hot when it's still within the normal range. We run into this often over on the Cherokee board. The center of the normal range for an XJ Cherokee is 210°, which is rather hot compared to a lot of other vehicles. Sometimes someone will buy one and post a panicked message on the board that his Jeep is overheating, when it's rock solid on 210. Or you'll get someone freaking out that his temp went to 220° out on a slow speed rock crawl, when that's still considered normal. Having a hybrid idiot gauge instead of a real temp gauge would help some of the more paranoid types from becoming unnecessarily agitated.

Originally Posted by go_a_way1

My hope would be to keep oil/coolent temps down a little in traffic. Now I think about it, it seems kinda pointless haha!!

Weirdly enough, it doesn't seem to matter. When my coolant temp hit 180° earlier, my oil temp was at 150°. If I go flog it at high RPM for a while, I can get the oil temp up to 225°, yet the coolant temp will still be under 195° with the A/C on.

Even though it relies on the vehicle's own sensors, running Torque and monitoring coolant and oil temps can give you an interesting picture of what's actually going on in your car. The only thing better would be to run separate aftermarket coolant and oil temperature gauges, but that's really overkill unless you track your car.

[go_a_way1]

@extrashaky
I run autometer for my oil temp and it sits just over 220F on hot days thats why I want to bring it down a little haha! I have no idea what my coolent it though, But thanks for your insight!