Cooling Issue - Street & Track

[bimmer]

Hi All,

I’m at a bit of a loss with a cooling issue I’m having. The coolant temp gauge will move up to the third dot when driving around the street (mainly with A/C on or going up steeper hills) and on track will easily move into the red. Max temp I saw on the street was 210 degrees @ ambient 90 degrees and on track I saw 242 degrees @ ambient 100 degrees halfway through one hot lap before backing off and calling it a day.

I wasn’t measuring exact coolant temps when I did a track day earlier in the year at ambient 75-80 degrees but while I could sneak a hot lap in, I easily was in the red by end of the lap and then had to do a cool down lap or two to get it back down.

When I was living in CT I would experience the gauge go up to the third dot on the track, and occasionally a little further if I was really pushing, but it got significantly worse after moving to CO, presumably because of the heat and thin air.

All the below parts have been replaced without much if any improvement and I’ve also included compression test results. I've also bled the system so many times now that I've lost count. I'd be amazed if there was any air present. I’m open to any and all suggestions as I’m very lost with what to check next…

Location: Denver Suburbs, CO (High Plains Raceway for Track)

Coolant / Distilled Water Mix: Started with 50/50, Moved to 20/80 (slight improvement but not significant), Added Water Wetter (actually got worse).

Cooling Components Replaced:
OEM BMW Radiator (Then replaced with CSF Rad to try to improve cooling to no avail)
OEM BMW Water Pump
CSF Oil Cooler (This did help oil temps quite a bit, but no effect on coolant temps)
Radiator Hoses
Thermostat
Aux Fan Switch
Coolant Temp Sensor (under intake manifold)
All Cooling System O-Rings
Pulleys, Tensioners, Belt
Fan Clutch / Fan Blades
Expansion Tank & Water Pipe Connecting Line
AC Condenser was replaced within last year, and has no blockages.
All air ducting, fan shroud, etc. is in place and secured

Compression Test Results (hot engine, 10 cranks):
Cylinder 1: 157 PSI
Cylinder 2: 155 PSI
Cylinder 3: 155 PSI
Cylinder 4: 155 PSI
Cylinder 5: 160 PSI
Cylinder 6: 160 PSI

[Estoril]

Given everything you wrote - I'd say that you still have air in the system somewhere. The OE radiator, water pump et al should be able to keep track temps under full control at 100F ambient. Certainly with 80% distilled H2O. I will run this weekend at an event that is always 98-100F and have no temp creep.

I'd chase it as suspected air despite your flushes.

[yhp2009]

Hi All,

[FONT=Calibri] Max temp I saw on the street was 210 degrees @ ambient 90 degrees and on track I saw 242 degrees @ ambient 100 degrees

Those temps for oil seems normal to me. Are you saying the oil temps were normal while the coolant temps were in the red?

[sapote]

All coolant temp measurements with AC turned on including at the track?

[bimmer]

Yup oil temps were fine, the temps I measured/mentioned are for the coolant. Measuring via OBD and confirmed OBD accuracy through the instrument cluster menu.

The measurements were all done with AC off. At the track I even had the heat blasting at full temp to try and aid the cooling system.

I really don't think it's air given the # of times I've bled the system. I had the front up in the air, ignition on 2, heat at 91 with low fan, temp dial on red, and watched coolant flow out of the bleeder without any bubbles for 30 seconds last night. Heat comes out of the vents piping hot. I understand air is a usual culprit when overheating occurs after replacing the entire cooling system, but I don't know where else it would be trapped...

[yhp2009]

If bleeding doesnt fix it, then i wonder if it could be the coolant temp sensor. Hate to suggest it since looks like you already did it with the refresh

[sapote]

* You have clean Condenser and Radiator, so air flow through the cooling fins is not the issue.
* At track high speed, more than enough air flow through the above items, so the issue is not caused by the fans functioning.
* This leaves us to only this: not enough coolant flow through the radiator. I would do this: with the display showing 97C coolant temp, grab the rad lower hose in your hand and see if you can hold it for 40 sec without crying. If no tears then it is the weak coolant flow issue.

M3 system is a self-bleeding, but I would do this if I were you:
Engine cold, with the existing coolant in the system:
Fill the tank to MAX marker, then cover the tank with the cap and turn one turn to keep it from falling off.
Turn on heater to max and fan, run the engine at idle. Important: Don't run the engine more than 7 minutes with the tank cap not tighten to avoid micro-boiling near the EX valves. Rev up the engine to 3000 rpm for 2 sec, then idle. Repeat 4 times. Keep it idling.
Crack open the bleeder for any air out, and close it when no more air bubbles flow out.
Top off the tank to MAX marker. Close the tank cap. Take a test drive.

[bimmer]

yhp2009 - I actually replaced the sensor as a means of trying to fix this issue, not during the refresh, so I know that is not faulty.

sapote - thanks for the suggestion. I will go give that a try now and report back.

[bimmer]

sapote - no luck. I started with your bleed procedure and did not get any air out of the bleed screw but let it leak for a bit just in case it was taking it's time. I took it for a test drive and 4-5 pulls in 2nd gear from 5k-7k rpms with the AC on was all it took to get the display to show 97C coolant temp / around the third dot on the gauge. I felt the lower rad hose and it was hot enough to burn my hand after about 5 seconds.

[sapote]

[USER="1470"]. I felt the lower rad hose and it was hot enough to burn my hand after about 5 seconds.

So, for whatever the reasons the rad could not rid the heat off fast enough.
1) measure battery voltage (directly at battery) with engine running. Not enough charging voltage means AUX fan is not running fast enough.
2) coolant system is properly working and pushing coolant volume fine. Did the AUX fan running fast at the overheated condition? old aux fan and new lower hose sensor, and if the fan driver is not 100% healthy then fan might not run at full speed. Do you know if the aux fan runs -- self test mode -- every time car first started?
3) At 97C, roll up some paper use it to stop the clutch fan blades by touching it on the rear side. Take a video.

[enjoy_m3]

Looks like you've done everything. Maybe start working backwards thru process of elimination? Remove the thermostat and the run the car without one and see if it gets better or worse. Just food for thought, I replaced the fan clutch on my e30 with a new one, car started to overheat after hard driving and then idling. Realized the new fan clutch was faulty, replaced with another and fixed the issue. Car shouldn't overheat without aux fan. I'm running no aux fan, spal radiator fan and no radiatior shrouds. Car runs fine without issue (temps only go up in over 100 degree heat after 4-5 hot laps, likely due to heat soak). The only thing I can think of is if maybe your block/head has a clog in one of the passages? I'm only throwing a guess though. Hope you figure it out

[sapote]

Remove the thermostat and the run the car without one and see if it gets better or worse.

This is not easy to achieve although it sounds simple. With no additional tube in the empty Tstat housing to divert the coolant, the pump just circulates the coolant around without any coolant flowing through the head, it will overheat badly.

OP couldn't hold his hand on the radiator lower hose for more than 5 sec, and this means there was plenty of hot coolant flowing through the rad and the Tstat was wide opened.

[enjoy_m3]

Ah you're right, good point

[bimmer]

So, for whatever the reasons the rad could not rid the heat off fast enough.
1) measure battery voltage (directly at battery) with engine running. Not enough charging voltage means AUX fan is not running fast enough.
2) coolant system is properly working and pushing coolant volume fine. Did the AUX fan running fast at the overheated condition? old aux fan and new lower hose sensor, and if the fan driver is not 100% healthy then fan might not run at full speed. Do you know if the aux fan runs -- self test mode -- every time car first started?
3) At 97C, roll up some paper use it to stop the clutch fan blades by touching it on the rear side. Take a video.

1. 14.05v while running
2. Just went out and got it back up to 97C and the AUX fan was running pretty fast. It also turned on right when I turned the car on, but I can continue to monitor this to make sure it does it every time.
3. Rolled up newspaper could not stop the mechanical fan with coolant temp at 97C. It started to shred the end. Video attached

[bimmer]

Video seemed to have issues uploading. Here it is on YouTube: https://youtu.be/ITb3pH_bXHg