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E46 M3 overheating


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I am posting this on behalf of a good friend.

 

The  car is an 05 e46 M3 and we attended an m-club trackday back in February together and his car overheated (went to red on the stock water gauge) after a few laps. Since then he has replaced the entire cooling system, mishimoto radiator, new oem thermostat, new hoses, new temp sensor, new fans, water pump, mishimoto oil cooler and cleaned out the condenser from all the bugs. He also added water wetter to the oem bmw coolant mix. We spent 2 hours together making sure there is no air in the system and tested the car. It seems that nothing happened after all this, the car overheats very easily in 100F degree weather with the a/c on, this happens just driving slow, and with the heater on it takes just about 1/2 minutes of hard driving (on the street). We extracted some coolant in order to make sure its not a headgasket problem and the coolant comes out just fine, no oil or any residue in it. The oil temperature is very well controlled, especially now with the new oil cooler but the water temps go up very fast. Last week he installed an aftermarket water temp gauge right after the water pump which theoretically should read higher than the oem gauge but it actually reads lower by 3-4 degrees (compared to the obd2 reading). So he is logging 217-220 degrees depending on the gauge with just a couple of minutes of hard street driving. Clearly if he is to come to the track he will see higher temps than that and possibly blow a gasket. He just ordered a lower temp thermostat hoping this will fix the problem (while cause other problems with obd2). Does anybody have any ideas on what might be the problem? I see plenty of e46s at the track so clearly its not an m3 issue but there is something wrong with the car.

 

Thanks

Thanasis

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The OEM radiator probably needed to be replaced. But he replaced it with sub par parts. The problem is the Mishimoto parts. Basically they are crap. I went through the same issues after installing a Mishimoto radiator in my e46 M3. I am running the Bimmerworld oil cooler. I went back to an OEM radiator and everything is better. With OEM I will hit 166 - 190 on the street and max 205 on the track. With Mishimoto I hit 200 on the street and 218 at the track. The Mishimoto cannot keep up with the S54. It has fewer rows than the OEM radiator.

 

Direct your friend to this thread. http://www.m3forum.net/m3forum/showthread.php?t=447276

 

The motorsports thermostat is not going to make the car run cooler. It will only prolong the time until it overheats. It will also cause a CEL on the street because the car will not get up to temp on the street.

 

The best setup for track is bimmerworld CR radiator, oil cooler, oil diverter, and 80C thermostat.

 

A good track is bimmerworld oil cooler, OEM radiator, 80C thermostat.

 

You need to measure the temps coming out of the motor and out of the radiator. When I did this I was amazed to find how poor the Mishimoto performing at cooling the water. This is a video where I rev the motor while measuring the in/out temps.

https://www.youtube.com/watch?v=j1pGeguAjuQ

 

Have him PM if he has question.

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The e46 M3 has a mechanical fan on the waterpump shaft. The e92 M3 uses an electrical fan.

 

The e46 M3 has an electric AUX fan in the front but it is designed for slower speeds.

 

(from BJ)

The Aux fan is controlled by the temps read at the radiator outlet sensor. The fan is completely ECU controlled, unlike the E36 which used a simple thermal switch.

 

Ignoring A/C there are two tables in the ECU that controls the fan.

 

The first is Temp vs. Fan Speed.

 

120* - 0%

122* - 30%

158* - 40%

176* - 65%

185* - 83%

194* - 100%

 

The second is Vehicle Speed vs. Voltage%

0 mph - 100% V

31 mph - 100% V

62 mph - 100% V

74.5 mpg - 50% V

87 mph - 0% V

124 mph - 0% V

 

Remember that this is measured at the outlet.  So, if the engine outlet says 210*, chances are that the radiator outlet is less than 194*.  This means that the fan will only run at 83%.  Now if the car is moving at 75mph, the speed is reduced another 50%, or a resulting ~40% fan speed.  Make sense?

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Make sure that all of the plastic parts/shrouds/shields are still in place and unmodified. At speed, cooling comes from air being directed (forced) through efficient heat exchangers.

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Make sure that all of the plastic parts/shrouds/shields are still in place and unmodified. At speed, cooling comes from air being directed (forced) through efficient heat exchangers.

Noted thank you. He bought the Bimmerworks radiator and oil cooler and we are installing them as we speak. Hopefully we can get him back on the track

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The e46 M3 has a mechanical fan on the waterpump shaft. The e92 M3 uses an electrical fan.

 

The e46 M3 has an electric AUX fan in the front but it is designed for slower speeds.

 

(from BJ)

The Aux fan is controlled by the temps read at the radiator outlet sensor. The fan is completely ECU controlled, unlike the E36 which used a simple thermal switch.

 

Ignoring A/C there are two tables in the ECU that controls the fan.

 

The first is Temp vs. Fan Speed.

 

120* - 0%

122* - 30%

158* - 40%

176* - 65%

185* - 83%

194* - 100%

 

The second is Vehicle Speed vs. Voltage%

0 mph - 100% V

31 mph - 100% V

62 mph - 100% V

74.5 mpg - 50% V

87 mph - 0% V

124 mph - 0% V

 

Remember that this is measured at the outlet.  So, if the engine outlet says 210*, chances are that the radiator outlet is less than 194*.  This means that the fan will only run at 83%.  Now if the car is moving at 75mph, the speed is reduced another 50%, or a resulting ~40% fan speed.  Make sense?

Makes sense. His fans are working ok though, the overheating happens at speed (mostly)

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The OEM radiator probably needed to be replaced. But he replaced it with sub par parts. The problem is the Mishimoto parts. Basically they are crap. I went through the same issues after installing a Mishimoto radiator in my e46 M3. I am running the Bimmerworld oil cooler. I went back to an OEM radiator and everything is better. With OEM I will hit 166 - 190 on the street and max 205 on the track. With Mishimoto I hit 200 on the street and 218 at the track. The Mishimoto cannot keep up with the S54. It has fewer rows than the OEM radiator.

 

Direct your friend to this thread. http://www.m3forum.net/m3forum/showthread.php?t=447276

 

The motorsports thermostat is not going to make the car run cooler. It will only prolong the time until it overheats. It will also cause a CEL on the street because the car will not get up to temp on the street.

 

The best setup for track is bimmerworld CR radiator, oil cooler, oil diverter, and 80C thermostat.

 

A good track is bimmerworld oil cooler, OEM radiator, 80C thermostat.

 

You need to measure the temps coming out of the motor and out of the radiator. When I did this I was amazed to find how poor the Mishimoto performing at cooling the water. This is a video where I rev the motor while measuring the in/out temps.

https://www.youtube.com/watch?v=j1pGeguAjuQ

 

Have him PM if he has question.

 

 

/thank you very much. The radiator and oil cooler were replaced and we drove the car flat out  for a really long time. Oil and water temps were perfect. Your advise was greatly appreciated by both my friend and myself

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Guys thanks for all your input. I am the guy that had the overheating issues. It looks like Mishimoto radiator for E46 M3 is wrongly designed. I think the radiator is oversized and the coolant velocities are too low so that makes the radiator inefficient.  Bimmerworld's CR solved the overheating problem.

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  • 3 months later...

Just want to piggy back on this thread a bit. Last track day at TWS I started getting coolant temps creeping towards red. Never had this happen before, even in higher ambient temps. The car is also S54 powered, only 35k miles on original pump/fan/rad, filled with BMW coolant mix. The car isn't a track car, so I don't want to drain and fill with a water/Water Wetter mix.

 

Just curious if adding Water Wetter to the normal BMW mix would make a difference. Redline claims it can be used as just an additive to normal coolant, but I can't find much in the way of experiences with this. The car isn't overheating, but it did force me to back off a couple laps.

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