Cooling system struggles

[Dave092]

Hi all,

I’m trying to get a clear idea of what normal/safe coolant temps really are on these cars, because I keep finding conflicting info. Some say the gauge should never move past center, while others say temps in the 230°F range are acceptable briefly if they come back down.

For reference, I’m in SoCal (near Mt. Baldy), and this only happens on hot days (90°F+) during sustained high-speed driving or spirited uphill runs. Around town, in traffic, or even idling with the A/C blasting, the car behaves perfectly normal temperature wise.

Using my Topdon Phoenix Smart, I’m monitoring what appears to be the coolant temp sensor under the intake manifold and the radiator outlet temp. I notice the gauge starts creeping right of center at about 203°F (with radiator outlet temps in the low–mid 190s). If I stay in it, the temps keep climbing—by around 219°F coolant temp and ~210°F at the radiator outlet, I’m in the red on the gauge.

The part that’s throwing me off is how quickly it comes back to normal. As soon as I back off, temps drop fast and the gauge comes back toward center, especially if I turn off the A/C.

The cooling system was fully refreshed about 5k miles ago with OEM BMW components, aside from a Nissens radiator (fully aware I should replace with OEM). That said, the behavior was very similar even before the original OEM radiator was replaced. The only thing I haven’t replaced yet is the coolant temp sensor under the manifold, which I plan to do soon. The condenser and oil cooler are original but appear clean with minimal bent fins.

I guess my main concern is that I’m seeing ~219°F and the gauge is already near red, which doesn’t seem to line up with the idea that ~230°F is “acceptable.”

Curious what others are actually seeing for real coolant temps under load (not just gauge position), and whether this behavior sounds normal or not.

Thanks in advance for any insight.

[sapote]

Using my Topdon Phoenix Smart, I’m monitoring what appears to be the coolant temp sensor under the intake manifold and the radiator outlet temp. I notice the gauge starts creeping right of center at about 203°F (with radiator outlet temps in the low–mid 190s). If I stay in it, the temps keep climbing—by around 219°F coolant temp and ~210°F at the radiator outlet, I’m in the red on the gauge.
.

You should post temp in C and not F as we all know boiling water is 100C.
219f = 104C, and this should not be in the red on the gauge. Maybe the gauge or its software is not virgin.
210 = 99C. This is not normal for rad outlet as it should be around 80C. This tells me not enough air flow through the rad; efan not running at full speed or dirty condensor/rad.

[Dave092]

You should post temp in C and not F as we all know boiling water is 100C.
219f = 104C, and this should not be in the red on the gauge. Maybe the gauge or its software is not virgin.
210 = 99C. This is not normal for rad outlet as it should be around 80C. This tells me not enough air flow through the rad; efan not running at full speed or dirty condensor/rad.

Noted, will do in the future!
The fan seems to be running at full speed but why would this matter at highway speeds? I will verify that it's reaching 100% just to be sure. The condenser and radiator are perfectly clear externally. I recently washed them out with no change.

How would I go about determining if the gauge or software are not virgin? Or better yet, what version I should have?

Will attach pictures of what I'm seeing on my end.
Keep in mind, this is under hard uphill canyon road conditions when these pictures were taken on a rather hot day.

[6speedS54]

while engine is running stick a news paper next to the fan in-front of the radiator to try to stop the fan, see if the fan stops. If it does your viscous clutch is gone.

[jayjaya29]

while engine is running stick a news paper next to the fan in-front of the radiator to try to stop the fan, see if the fan stops. If it does your viscous clutch is gone.

Do this while the car is at operating temperature.

[sapote]

I think the stock gauge for M3 is similar to this con-M gauge with real degrees overlay as below, although we should ignore the buffered zone at the middle [75 to 115] for the M3.
So the start of the red zone is about 120C, but your reader shows 104C. This is why I think your gauge is not stock.

[Dave092]

while engine is running stick a news paper next to the fan in-front of the radiator to try to stop the fan, see if the fan stops. If it does your viscous clutch is gone.

Fan clutch has been replaced with the OEM BEHR unit. Additionally, this issue is only happening at highway speeds. Typically over 55-60MPH under heavy load when I believe the fan clutch is no longer doing anything but blocking air flow anyways. On the way home from my last track day out at Chuckwalla I was running close to red doing 90mph up a hill on the 10 freeway out in the desert. Fans as far as I've ever known are not the issue at this speed. The car will quickly come back down to center as soon as I'm going closer to 40mph with light throttle.

[Dave092]

I think the stock gauge for M3 is similar to this con-M gauge with real degrees overlay as below, although we should ignore the buffered zone at the middle [75 to 115] for the M3.
So the start of the red zone is about 120C, but your reader shows 104C. This is why I think your gauge is not stock.

This is interesting. Im going to look into this. Thank you!

[heinzboehmer]

I think the stock gauge for M3 is similar to this con-M gauge with real degrees overlay as below, although we should ignore the buffered zone at the middle [75 to 115] for the M3.
So the start of the red zone is about 120C, but your reader shows 104C. This is why I think your gauge is not stock.

M3 values differ by quite a bit: https://www.e46fanatics.com/posts/15832087/

[Dave092]

M3 values differ by quite a bit: https://www.e46fanatics.com/posts/15832087/

Well this is interesting... Based on the values you provided my gauge is operating perfectly. If thats the case, how are people claiming to run over those values and still be in the middle? Im not convinced people are doing Texas and SoCal track days with their coolant temp never passing 105C which seems to be still within acceptable operating temp? Ive seen dozens of posts with people stating they "never pass center" Yet past center doesn't seem at all like an extreme coolant temp according to the data you provided. Per my data, I start falling just to the right of center at exactly 95C.

[heinzboehmer]

Well this is interesting... Based on the values you provided my gauge is operating perfectly. If thats the case, how are people claiming to run over those values and still be in the middle? Im not convinced people are doing Texas and SoCal track days with their coolant temp never passing 105C which seems to be still within acceptable operating temp? Ive seen dozens of posts with people stating they "never pass center" Yet past center doesn't seem at all like an extreme coolant temp according to the data you provided. Per my data, I start falling just to the right of center at exactly 95C.

Yeah at hot track days, I start noticing the gauge moving towards the red at ~100C. I'm not staring at it cause of the driving thing, so starting to move at 95C sounds about right.

In logs, I've seen temps drop from 105C to 95C in the span of just the front straight, if I shift at 7k.

[sapote]

M3 values differ by quite a bit: https://www.e46fanatics.com/posts/15832087/

Thanks. I didn't dig in much. So OP gauge at start of red zone at 104C is correct for a stock gauge, and the end of red zone is 115C, seems to be low for a cracked head??? Compared to the non-M that the start red is 125C which is too late for the driver to save his head.



Code:Non-M Default M3 Default Recommended non-M Function / Angle
0x0F (15ºC) 0x0F (15ºC) 0x0F (15ºC) Gauge Start (0º)
0x32 (50ºC) 0x3C (60ºC) 0x41 (65ºC) End of Blue (15.5º)
0x4B (75ºC) 0x55 (85ºC) 0x5A (90ºC) Center (Buffer Start) (45º)
0x73 (115ºC) 0x5F (95ºC) 0x64 (100ºC) Center (Buffer End) (45º)
0x7D (125ºC) 0x69 (105ºC) 0x6E (110ºC) Start of Red (79º)
0x8F (143ºC) 0x73 (115ºC) 0x73 (115ºC) End of Red or LED on?? (84º)

[6speedS54]

Fan clutch has been replaced with the OEM BEHR unit. Additionally, this issue is only happening at highway speeds. Typically over 55-60MPH under heavy load when I believe the fan clutch is no longer doing anything but blocking air flow anyways. On the way home from my last track day out at Chuckwalla I was running close to red doing 90mph up a hill on the 10 freeway out in the desert. Fans as far as I've ever known are not the issue at this speed. The car will quickly come back down to center as soon as I'm going closer to 40mph with light throttle.

Are you the original owner? have you tried checking radiator temperature with temperature gauge to see if there is any blockage?

Was there any rust in the cooling system when you were refreshing it?

I recently refreshed my cooling system as well with the new radiator 2 weeks ago or so. I also had an issue when its 95+ outside and AC on with temps creeping higher. I haven't had a chance to test It yet, but replaced my fan clutch last week when I discovered it was spinning by hand. I did find rust in my system which I flushed out with a chelating agent, had to flush the system with distilled water 10 times to remove the flakes.

[sapote]

104C went in the rad and 99C went out is not normal as with proper air flowing the outlet should be around 80C.