Stock operating temperature questions...

So, the motor in my 2008 GT is stock and untouched except for a BBK CAI. I installed an Autometer Cobalt water temp gauge along with an oil psi and voltmeter. Yesterday, while cruising normally, I noticed a rather large temperature swing between the fan cut in and cut off temps. At a stop light, water temp will creep up to +/- 230F and then settle back in between 200F and 210F while cruising. In the world I come from (64-72 American muscle cars and 79-93 fox body mustangs) 230F is overheating or damn close to it. Ambient temperature was about 85F and relative humidity was about the same.

My question is, what is the stock setting for cooling fan cut in/cut off temps? Are the temps I'm seeing normal for this platform? Can these setpoints be adjusted with a tune? Thanks in advance for the help and I hope I've been clear.

Chris

Where is the temperature sensor placed in the system? Did you have the ac on? You should see close to tstat temp when cruising. So around 190 degrees, and 210-220 sounds about right for sitting idling with ac on on a warm day. Yes you can adjust the fan low and high speed temps in the tune.

The 2008 4.6L 3V thermostat starts to open between 188-195*F and is fully open at 208-215*F.

Jeremy@S&H Performance said:

Where is the temperature sensor placed in the system? Did you have the ac on? You should see close to tstat temp when cruising. So around 190 degrees, and 210-220 sounds about right for sitting idling with ac on on a warm day. Yes you can adjust the fan low and high speed temps in the tune.

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The sensor is placed in the coolant crossover. The air conditioning was on. Does the fan run on high speed at all times whenever the a/c is on in order to pull heat from the condenser?

tmcolegr said:

The 2008 4.6L 3V thermostat starts to open between 188-195*F and is fully open at 208-215*F.

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Thanks! Is it safe to assume the fan setting track those temp ranges closely?

08 Vapor said:

The sensor is placed in the coolant crossover. The air conditioning was on. Does the fan run on high speed at all times whenever the a/c is on in order to pull heat from the condenser?

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Good spot then, yes there is relay that turns the fan on high speed when ac is on.

08 Vapor said:

Thanks! Is it safe to assume the fan setting track those temp ranges closely?

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No not exactly, but close. The fan has its own air temp sensor that measures air being pulled through the radiator core. These are the temps the pcm reads to signal fan speed changes and on/off. Your coolant temps coming out of the engine at the crossover will read a tadhigher than this air being pulled from the rad core. In general you want you fan temp settings in tune with the tstat coolant temps though. Its not a good ideal to just drop the fan temp speeds as it can lead to the fan always being on and not being able to kick off etc.

This is the guidline I follow. On cold start let the car warm up as you watch the water temp gauge. When the stat fully opens there will be a good 1 minute pause in the temp rise. Set your low speed fan right above this. On my car( I have a 170 degree tsta). This pause is at 175 degrees on my water temp gauge so I set my low speed fan to come on at 180. This way the low speed fan isnt sitting there running all the time when crusiing down the highway etc. Then set your high temp fan to 10-15 degrees above low. Mine is set at 192 degree iirc. So baicly fan off when cruising come to a stop low speed kicks on to keep temp down, then the longer you sit high speed will start kicking on and off to keep the car from over heating, and like mentioned with the ac on it kicks straight to high speed fan on and off as needed when sitting still.

There's a speed (mph)setting to set the mph the fans turn on/off as well in the tune so they don't stay on when cruising.

Thanks for the info guys. I'm going to do some more monitoring under different conditions and try to get a better idea of what's really going on here. If I have to start troubleshooting, I'm sure I'll be posting back in here.

The PCM will command-on the low and high speeds under different conditions. The lower settings in the tune are not necessarily best, because as mentioned, the fan can end up staying on low or high while cruising.
I connected a couple od LEDs to see when the PCM is turning the low speed on, or high speed on, as well as a switch to force the fan on when i want it on. Just going by the coolant temps on an aftermarket temp gauge (with sensor located in crossover before it returns to the radiator), it was not clear when the fan was coming on, especially when the coolant temps got hot when idling. I thought at times the fan was not working at all, which it was.
Knowing when the fan is told to come on, knowing when it is on, and seeing the coolant temps, is all very helpful in understanding your cooling situation.

I had made the 'mistake' of adding a secondary trans temp cooler on top of the stock cooler, piggy-backing them on top of each other (for auto trans). Turns out that was blocking too much air to the radiator and causing the car to run hotter. Removing it helped restore temps and cooling to better levels.

JeremyH said:

This is the guidline I follow. On cold start let the car warm up as you watch the water temp gauge. When the stat fully opens there will be a good 1 minute pause in the temp rise. Set your low speed fan right above this. On my car( I have a 170 degree tsta). This pause is at 175 degrees on my water temp gauge so I set my low speed fan to come on at 180. This way the low speed fan isnt sitting there running all the time when crusiing down the highway etc. Then set your high temp fan to 10-15 degrees above low. Mine is set at 192 degree iirc. So baicly fan off when cruising come to a stop low speed kicks on to keep temp down, then the longer you sit high speed will start kicking on and off to keep the car from over heating, and like mentioned with the ac on it kicks straight to high speed fan on and off as needed when sitting still.

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I know this comment is almost a decade old, but I've got a question. I've got a 2010 Gt that I put in a 170⁰ tstat like you did. But my coolant temps according to my handheld tuner shows that 190⁰ is where my coolant temp settles at on first warm up. With a 170⁰ tstat wouldn't my temperature settle much lower than 190⁰, I was kinda guessing 180⁰ maximum. What could be my issue?

TheCrowdPlow said:

I know this comment is almost a decade old, but I've got a question. I've got a 2010 Gt that I put in a 170⁰ tstat like you did. But my coolant temps according to my handheld tuner shows that 190⁰ is where my coolant temp settles at on first warm up. With a 170⁰ tstat wouldn't my temperature settle much lower than 190⁰, I was kinda guessing 180⁰ maximum. What could be my issue?

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The only issue you have is not understanding how an engine works. go back to your other post and read what I copied for you.

Y

TheCrowdPlow said:

I know this comment is almost a decade old, but I've got a question. I've got a 2010 Gt that I put in a 170⁰ tstat like you did. But my coolant temps according to my handheld tuner shows that 190⁰ is where my coolant temp settles at on first warm up. With a 170⁰ tstat wouldn't my temperature settle much lower than 190⁰, I was kinda guessing 180⁰ maximum. What could be my issue?

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Your handheld is measuring inferred temp. Not true water temp coming out of the motor I measure mine with a standalone gauge in the upper radiator hose. Btw I ended up putting my stock 192 back in the 170 was too cold for me car didn't run as good. My setup runs way better in the 190-200 range. Also my setup has a upgraded radiator fans, lower compression etc.

Fans dont do squat above 25mph or so. All air is pushed through the radiator from forward motion. Stick your hand out the window and feel the air resistance going dow the road @65 mph. Now, while stopped, feel how much air the fan is pushing.

AC turns on the fan based on the pressure transducer on the high pressure side. (Fan wont turn on with AC at highway speed)

The only time a.tune change to fan turning on matters is at idle/stoppes in traffic.

I would check your guage agains what the pcm is seeing before starting to chase a possible non-issue.
230* is a bit warm, but not that bad. Actual temp maybe only 200, which is normal.

The OBD does not measure actual coolant temps...it's inferred reading, based on an algorithm in the tune.
Which is partly based on cylinder head temps (CHT)..and IAT's etc. There is an actual sensor that measures CHT...and typ the CHT is aprx 10 deg F higher than the inferred ..'coolant temp'.

Check your CHT temps at the OBD port..and get back to us. CHT reading minus 10 deg F is probably what the actual coolant temp is. You can also open the lid on the coolant overflow plastic container, then measure the temp inside with either a thermometer...or a point and shoot IR gun.

Juice said:

Fans dont do squat above 25mph or so. All air is pushed through the radiator from forward motion. Stick your hand out the window and feel the air resistance going dow the road @65 mph. Now, while stopped, feel how much air the fan is pushing.

AC turns on the fan based on the pressure transducer on the high pressure side. (Fan wont turn on with AC at highway speed)

The only time a.tune change to fan turning on matters is at idle/stoppes in traffic.

I would check your guage agains what the pcm is seeing before starting to chase a possible non-issue.
230* is a bit warm, but not that bad. Actual temp maybe only 200, which is normal.

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Pentalab said:

The OBD does not measure actual coolant temps...it's inferred reading, based on an algorithm in the tune.
Which is partly based on cylinder head temps (CHT)..and IAT's etc. There is an actual sensor that measures CHT...and typ the CHT is aprx 10 deg F higher than the inferred ..'coolant temp'.

Check your CHT temps at the OBD port..and get back to us. CHT reading minus 10 deg F is probably what the actual coolant temp is. You can also open the lid on the coolant overflow plastic container, then measure the temp inside with either a thermometer...or a point and shoot IR gun.

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That's not gonna help this guy. He is wondering why, after changing thermostats, his car runs at the same temperature it did before. I tried to explain that the thermostat controls when the coolant starts to flow. He seems to think that by putting a lower temp thermostat in it would lower his engine temps. I tried to explain to him that the only way to drop cooling temps is to increase flow of coolant or air or a larger radiator and that by running a cooler thermostat just keeps your car from warming up as quickly.

TheCrowdPlow said:

I know this comment is almost a decade old, but I've got a question. I've got a 2010 Gt that I put in a 170⁰ tstat like you did. But my coolant temps according to my handheld tuner shows that 190⁰ is where my coolant temp settles at on first warm up. With a 170⁰ tstat wouldn't my temperature settle much lower than 190⁰? I was kinda guessing 180⁰ maximum. What could be my issue?

Click to expand...

The operating temperature of your engine will depend on the balance between engine heat production and heat rejection (coolant flow rate through radiator, airflow rate through radiator, latent heat of the coolant). The 4.6 3V was designed to run between 190-200*F. If you want it to run 20*F cooler than that, you're going to need more cooling capacity (thicker radiator) as well as a 170*F thermostat.
At the end of the day there IS no issue except for your apparent obsession with making the engine run cooler than it was designed for and take longer to warm up. That's the exact opposite of what you want if you live in a cold climate.