My coolant temperatures, data-logged

Twisted2

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The past few weeks, I've been reading way too much about engine coolant temps, trying to determine whether or not my '96 is running hot. It certainly seemed to be, in city traffic, A/C on, and the needle on the stock gauge routinely parked over the "L" in NORMAL. I mean it, I'd been up till barbaric hours of the mornings, reading about what temps are normal for the serpent. Finally, I picked up an SCT tuner, and did a few data-logs on my laptop, in ambient temperatures of about 87 degrees, in pretty high humidity.

My average running temperature was around 204 degrees in stop and go city traffic, with the A/C on. At this temperature, my stock gauge needle was at the beginning of "A" on the dial. Sitting still, the needle rose to the end of "L." Here's the shocker: as it turns out, with the needle at the end of "L," we're talking actual temperatures of only about 216 degrees, maximum. I've confirmed this temperature at the crossover coolant pipe with my infrared thermometer gun--although this temperature differs quite a bit, depending on where on the pipe you aim the device.

Anyhow, my thoughts on this whole experiment:

1. These temperatures are perfectly fine, with 216 as a max.
2. My stock gauge is a drama queen, prone to hysterics and hyperbole.
3. Once the gauge reaches the middle, it begins to speak in loud terms of rather tiny changes. On my gauge, the needle moving from the end of the letter "M" to the end of the letter "L," only represents about an 8-10 degree change in actual coolant temperature.
4. The sensitivity of the stock gauge varies widely from one car to the next. A cat on another forum (maybe it was this one) was animate that by the time the stock gauge reaches "L," your coolant temperature is 250 degrees, and that you've not only warped your heads, but destroyed your marriage and all your friendships, lost your job, and that anything remotely pleasurable in your life, from there on, will be swiftly replaced by excruciating pain. Maybe I'm exaggerating a little, too...but my temps are nowhere near 250 with the needle on "L".

Anyhow, does anyone have any thoughts or experience on any of this? Thanks.
 
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mwolson

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Your temps are consistent with the ones I see.

It is very good that you are taking data. Most people just freak out, and try to make their engines run too cool.

The gauges do vary a lot from car to car. Most gauges are more sensitive at the extremes of the gauge and less sensitive in the Normal range from what I have seen.
 

fake

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Good info to know. While this is my sixth Mustang, this is my first Cobra. I too was concerned when my needle would sit between the M & A while in the city. Guess I have nothing to worry about.
 

Twisted2

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Your temps are consistent with the ones I see.

It is very good that you are taking data. Most people just freak out, and try to make their engines run too cool.

The gauges do vary a lot from car to car. Most gauges are more sensitive at the extremes of the gauge and less sensitive in the Normal range from what I have seen.

Thanks for the replies, folks. Indeed. I only half-understand the assumption that colder is always best. IMO, proper running temperatures are what is best.

Anyhow, I've always used Autometer gauges in the past, but with this car, I just wouldn't know where to mount any. I prefer my gauges low profile, instead of up where everyone can see them. With this car, I'd have to eliminate my CD player, I guess. I just love the look of the stock layout too much to mess with it.


Good info to know. While this is my sixth Mustang, this is my first Cobra. I too was concerned when my needle would sit between the M & A while in the city. Guess I have nothing to worry about.

Agreed...it doesn't seem like you do have anything to worry about. To be sure, you could get an infrared thermometer and check. I got mine from Pep Boys. It was supposed to be $40, but for some reason, they only charged me $14. I didn't argue with the man:).
 

STAMPEDE3

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I've been telling people here for several years that the stock gauge is not inaccurate as most think but it is a very narrow range.
 

Twisted2

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What's weird is the sweep of the thing. It seems like the bottom half of the gauge represents 100 and some-odd degrees, while the top only represents 15 or 20. Hard to get my head around that.
 

97RioRed4V

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My gauge is normally in the middle when I am cruising along. Then when is hot out and ac on it moves to the letter A. I was starting to wonder if something was wrong. Thanks for the info.
 

Twisted2

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No problem. Another thing I forgot to mention. I can always make my gauge read a half-letter hotter simply by pressing the window up (or down) buttons when the windows are already up (or down). To a lesser degree, turning on headlights or stepping on the brake nudges the needle a up a smidgen too. So system voltage is tied in to the gauge readings somehow. Strange animal, the stock gauge.
 

fake

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My gauge is normally in the middle when I am cruising along. Then when is hot out and ac on it moves to the letter A. I was starting to wonder if something was wrong. Thanks for the info.

Weird. When I turn on my AC, my temp drops.
 

Twisted2

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Weird. When I turn on my AC, my temp drops.

I've heard other people say that. I wonder why that varies between different cars, and if it's an indication of the condition of the radiator. With mine, after the initial voltage drop (and temp needle increase) of turning the A/C on, it seems like it starts to cool the car down. Then, within a few minutes, it's hotter than it would have been if I'd left the A/C off.

Via my data log, the temp seemed to start dropping the second I turned the A/C off. Then, even though I was already dripping sweat, I cranked the heat just to see what would happen. Within about a minute and-a-half, the temp dropped from like 210 to 196-198. The heater core seems more effective at cooling the engine than the actual radiator. Lol.
 

stanggirl14

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No problem. Another thing I forgot to mention. I can always make my gauge read a half-letter hotter simply by pressing the window up (or down) buttons when the windows are already up (or down). To a lesser degree, turning on headlights or stepping on the brake nudges the needle a up a smidgen too. So system voltage is tied in to the gauge readings somehow. Strange animal, the stock gauge.

Mine does this, and my aftermarket gauges do as well, they'll be 5-10 degrees in the aftermarket gauges I have, I so have to tap into another power supply.

Weird. When I turn on my AC, my temp drops.

I believe the temps drop b/c when the ac is on the fan runs all the time, not just when the car reaches a certain temp. I could be wrong but I've read that on here before and my car does the same thing


Also, anyone have an idea why the stock gauge would read down around the O in normal while the aftermarket gauge reads 210 -220 degrees? I've got speedhut gauges (electrical) and the temp sensor is mounted in the crossover, I know I need to move it to the block and I know mechanical gauges are more accurate but after the hideous oil leak I went through I'm concerned about using mechanical ones. The only thing I can think of is b/c of it being mounted in the crossover. Any ideas would be greatly appreciated.
 

Twisted2

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Mine does this, and my aftermarket gauges do as well, they'll be 5-10 degrees in the aftermarket gauges I have, I so have to tap into another power supply.



I believe the temps drop b/c when the ac is on the fan runs all the time, not just when the car reaches a certain temp. I could be wrong but I've read that on here before and my car does the same thing


Also, anyone have an idea why the stock gauge would read down around the O in normal while the aftermarket gauge reads 210 -220 degrees? I've got speedhut gauges (electrical) and the temp sensor is mounted in the crossover, I know I need to move it to the block and I know mechanical gauges are more accurate but after the hideous oil leak I went through I'm concerned about using mechanical ones. The only thing I can think of is b/c of it being mounted in the crossover. Any ideas would be greatly appreciated.

From what I'm hearing, these stock gauges are like snowflakes.

I was thinking that the crossover tube would be an excellent place to mount a sensor, as it seems like it would read the highest temps. From what I saw on mine, the stock coolant sensors are also mounted in the crossover pipe. I'm curious, why did someone tell you to move the sensor into the block? And does your gauge ever read higher than O? Thanks.
 

stanggirl14

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From what I'm hearing, these stock gauges are like snowflakes.

I was thinking that the crossover tube would be an excellent place to mount a sensor, as it seems like it would read the highest temps. From what I saw on mine, the stock coolant sensors are also mounted in the crossover pipe. I'm curious, why did someone tell you to move the sensor into the block? And does your gauge ever read higher than O? Thanks.


No one told me to move it I've just read numerous posts that it's a more accurate place to put it in the block vs the crossover. I know the stock ones are in the crossover and not necessarily accurate. My stock gauge doesn't go over O often but in NC heat in traffic with the ac on it will. Before I changed the condenser it used to climb to the A and L routinely.
 

Twisted2

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No one told me to move it I've just read numerous posts that it's a more accurate place to put it in the block vs the crossover. I know the stock ones are in the crossover and not necessarily accurate. My stock gauge doesn't go over O often but in NC heat in traffic with the ac on it will. Before I changed the condenser it used to climb to the A and L routinely.

Understood. Block temps are probably more stable than head/cylinder temps. Good to hear that you noticed a difference when you changed your condenser. I'd been trying to justify doing that; it just sounds so expensive. Lol.
 

stanggirl14

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Understood. Block temps are probably more stable than head/cylinder temps. Good to hear that you noticed a difference when you changed your condenser. I'd been trying to justify doing that; it just sounds so expensive. Lol.

Not so much expensive but a PITA b/c you have to evacuate the ac system and legally it needs to be captured so I paid a shop to do it. You can refill it on your own with the cans but I had them recharge it. That's the expensive part IMO.

You'll be surprised at the 96 condenser, I'm not sure how any air got through it. Of course the sand we deal with in NC didn't help things either, it was pretty beat up when I pulled it.

Also, I changed to a fluidyne radiator at the same time which didn't seem to make a big difference, it ended up cracking and I replaced it with an aftermarket 97 and it's been the same. Then I got a tuner and changed the fan temp settings and haven't had an issue after that. Of course depending on how accurate the speedhut gauges are I may have more issues than I'm aware of, LOL
 

Twisted2

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Not so much expensive but a PITA b/c you have to evacuate the ac system and legally it needs to be captured so I paid a shop to do it. You can refill it on your own with the cans but I had them recharge it. That's the expensive part IMO.

You'll be surprised at the 96 condenser, I'm not sure how any air got through it. Of course the sand we deal with in NC didn't help things either, it was pretty beat up when I pulled it.

Also, I changed to a fluidyne radiator at the same time which didn't seem to make a big difference, it ended up cracking and I replaced it with an aftermarket 97 and it's been the same. Then I got a tuner and changed the fan temp settings and haven't had an issue after that. Of course depending on how accurate the speedhut gauges are I may have more issues than I'm aware of, LOL

Agreed. My stock condenser is dubious looking, at best. I wonder how that design managed to slip past quality control. Lol. I may look into having that done, as even though I know my cooling system is doing its job, I believe it's struggling to do so. If I may ask, how much did that swap cost you...minus the Fluidyne and so forth?
 

stanggirl14

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Agreed. My stock condenser is dubious looking, at best. I wonder how that design managed to slip past quality control. Lol. I may look into having that done, as even though I know my cooling system is doing its job, I believe it's struggling to do so. If I may ask, how much did that swap cost you...minus the Fluidyne and so forth?

You know it was so long ago I don't remember, seems like maybe $30-$50 to evacuate the system, $100 for the condenser if that and maybe $40-$50 to recharge it? I did the rest myself so saved a ton there. :)
 

Twisted2

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Ah. Thanks for the info. Wish I could do the work myself, but I'm a spinal case. I may get some quotes. I was imagining the swap being like a grand or something silly like that. Maybe it's not so bad. Anyway, thanks again!
 

stanggirl14

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Ah. Thanks for the info. Wish I could do the work myself, but I'm a spinal case. I may get some quotes. I was imagining the swap being like a grand or something silly like that. Maybe it's not so bad. Anyway, thanks again!

oh man, sorry to hear that. I do as much of my own work as I can, just don't trust many garages. LOL

I wouldn't think it would be that bad but I have no idea on shop costs these days, although they say header installs are really bad and they're usually under 1k.
 

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