Normal behavior of coolant temperature

[stephenkirsh]

So when it's really hot or I'm on the track, I turn on the exact coolant temp in the hidden menu.

I've noticed when it's really hot the coolant temp can dip as low as 85 degrees. I thought these cars run at 95 pretty much all the time.

My cooling system is all OEM with about 15k on it with a Stewart water pump.

I'm assuming this is relatively normal.

21120

[BMWCurves]

From this thread (http://www.zhpmafia.com/forums/showthread.php?6575-OBC-19-7-00-Watcha-go-doityourself), it seems like the cooling system works harder when under load, often dipping the coolant temp down into the 80s. Someone else can chime in.

[Oli77]

Yes, I have noticed too that when you pull hard on it, the coolant temp drops down considerably. It is apparently designed for improved performance. I think we have a different thread that addresses that.

[stephenkirsh]

Yea I know when you floor it it spins the water pump faster, so that makes sense. But when cruising on the freeway at 70, it's not working hard, other than its just hot outside.

I'm probably making a big deal about nothing.

[az3579]

Our temp gauges show a very wide range of temperatures in the middle position. I think it's something like the exact middle position being 75-110 degrees C. I have a corrected temp gauge, so as soon as the temp drops, my gauge will reflect that. When you push your car hard and you have factory gauge coding, your needle will not move at all to reflect the temp change. That is why you'll notice a discrepancy between your gauge and what the OBC says.

If you get PA Soft, you can correct your temp gauge to show actual temp, which I highly recommend.

sent from my Droid Turbo

[stephenkirsh]

Yea I'm well aware of the factory gauge, that's why I use the hidden menu option.

Everybody says the cars run right at 95 all the time, so I got curious when it dips into the 80s for extended periods of time (10-30 minutes).

[Oli77]

^ that's more weird, 10-30 minutes? Mine never does that.

[az3579]

Yea I'm well aware of the factory gauge, that's why I use the hidden menu option.

Everybody says the cars run right at 95 all the time, so I got curious when it dips into the 80s for extended periods of time (10-30 minutes).

Yeah it does that on especially hot days when the fan is always cooling at a higher rate. If you sit in traffic for extended periods, it may do that. I noticed sometimes I'll be sitting in traffic and it'll just be sitting there a little below halfway. It always goes down when I do a hard acceleration.

I wouldn't worry about it dipping into the 80s.

[Vas]

I have noticed after the coolant gauge temp mod for the gauge to drop as well after getting on it.

Much better then the factory buffer zone.

[NoVAphotog]

So when it's really hot or I'm on the track, I turn on the exact coolant temp in the hidden menu.


Hidden menu coolant temp? How is this brought up?

[Vas]

Hidden menu coolant temp? How is this brought up?

You have to do the gauge cluster test and then select one of the sub-menu for the coolant temp.

[danewilson77]

https://youtu.be/twM7NchxjXI

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[BMWCurves]

Is there a relatively easy way to program the thermostat to specific temperatures for a given situation? For example, idle at 96C after everything is warm? Or is that something you'd have to have changed in the DME?

[az3579]

Is there a relatively easy way to program the thermostat to specific temperatures for a given situation? For example, idle at 96C after everything is warm? Or is that something you'd have to have changed in the DME?

It is not adjustable in our E46s.

[BMWCurves]

It is not adjustable in our E46s.

Huh, you would think that would be something that could be easily programmed. Thanks for the info!

[JFern]

These cars run map cooling, meaning that for a given situation the DME will manipulate the electronically controlled thermostat to make the car run at the temperature that makes sense for the situation. For example, on steady state cruise the DME will make the thermostat open later so it runs at the ~95* that we're used to seeing. The higher temp is more fuel efficient. On the other hand, when you dip into the throttle the DME will open the thermostat so the car runs at a lower temp to better handle the additional stress and run optimal ignition timing.

This link is specific to the E38, but the concept is the same:

http://www.meeknet.co.uk/e38/E38_Map_Thermostat.pdf

[Oli77]

Thanks for the link!

Clealry : "lower coolant temperatures are intentionally set under full load operating conditions"

This begs the question then, about Stephen's temp story above. How could the temp drop for up to 30 minutes? Could you be "full load" for 30 minutes?

[stephenkirsh]

These cars run map cooling, meaning that for a given situation the DME will manipulate the electronically controlled thermostat to make the car run at the temperature that makes sense for the situation. For example, on steady state cruise the DME will make the thermostat open later so it runs at the ~95* that we're used to seeing. The higher temp is more fuel efficient. On the other hand, when you dip into the throttle the DME will open the thermostat so the car runs at a lower temp to better handle the additional stress and run optimal ignition timing.

This link is specific to the E38, but the concept is the same:

http://www.meeknet.co.uk/e38/E38_Map_Thermostat.pdf

Right, but my question is that when cruising on the freeway, I was seeing the temp dip into the 80s for extended periods of time, not 95. Hence the entire purpose of the thread...

[Oli77]

Right, you are not at full load under these conditions. Maybe this is a sign of the thermostat or control unit failing?

[JFern]

I've watched the temps dip under medium to heavy load, not necessarily full. That said, if you're seeing consistently lower temps on the highway, you may have a thermostat that's sticking open. There's more air passing over the radiator, and if the t stat is sticking open it may not be able to close far enough to get the temp where the DME wants it.

Are the temps normal at lower speed driving?


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[BMWCurves]

Right, but my question is that when cruising on the freeway, I was seeing the temp dip into the 80s for extended periods of time, not 95. Hence the entire purpose of the thread...

This was the symptoms I had. My car would never come to the middle of the temperature gauge no matter what I did. I assumed a stuck open thermostat but I was due for a cooling overhaul anyways so I swapped it with a new one. Now it warms right up and stays pegged in the middle.