Radiator fan running constantly and fix

[M4apex]

I didn’t find much on the F8x forums about this problem and the fix, so I wanted to share my experience and fix.

About a week ago I noticed that my radiator fan started running at full blast all the time, even when cold starting in the morning. When stopped at a red light, I could also hear the fan vary a lot in speed, which was weird. I checked coolant reservoir and all was ok.

Since my 10k miles service was already scheduled (for today), I just waited until I brought it in. At first they thought it was a water pump problem (I did read online that a constantly running radiator fan is a possible indicator of a soon-to-fail water pump), but they confirmed all was ok with the pump and no leaks in coolant system. Hmmm.

Then they checked the A/C system. According to my SA, BMW sometimes over-charges the system from the factory?? Sure enough, my system was over charged. BMW spec is 550gr, and my system was at 649gr. They re-charged the A/C system to the correct factory spec of 550 gr. This appears to have fixed the always-on fan problem. I’ve only driven it about 20 miles since picking it up from service, but the fan is not running constantly anymore.

I'll keep on eye on this to make sure the A/C over charge was the culprit, but just wanted to share with everyone.

Has anyone else had this fan-always-on issue, and the fix was A/C over charged?

[tom @ eas]

Never heard of the issue you are describing. However, thanks for taking the time to explain the problem and following up with a solution.

[M4apex]

well, I guess I spoke too soon. All was fine for a couple days. The radiator fan started running on high again a few seconds after starting the car this morning. And by the time I got to work (about 15 min drive), the radiator fan was varying a lot in speed from high to low, etc. I took a quick video at:

I'm dropping back off at the dealer this morning. I'll update when they figure it out.

[forza1976]

That is annoying, let us know what they find.

[M4apex]

yup... annoying!!

Quick update... a/c pressure sensor failed. Easy fix, but that caused over pressure condition in a/c system, which caused a/c compressor to fail. This apparently causes radiator fan to run on high with varying speeds, which is my symptom. Compressor is not in stock in US, so they are ordering from Germany, 2-3 weeks. At least its February and cold out! And bonus!!... they washed the M4, so saved me the time this weekend. I'll post an update after the new sensor and compressor are installed.

[Flupke]

Originally Posted by M4apex

yup... annoying!!

Quick update... a/c pressure sensor failed. Easy fix, but that caused over pressure condition in a/c system, which caused a/c compressor to fail. This apparently causes radiator fan to run on high with varying speeds, which is my symptom. Compressor is not in stock in US, so they are ordering from Germany, 2-3 weeks. At least its February and cold out! And bonus!!... they washed the M4, so saved me the time this weekend. I'll post an update after the new sensor and compressor are installed.

I find it strange that in all of the US BMW would not have a single compressor in stock. Also two to three weeks to ship it from Germany?? in today's environment, how about overnight DHL?

[M4apex]

Must be coming by boat!!

[racerblade]

I've got the same issue - taking it in to the dealer tomorrow. Amazing that this thing only 8K miles on it, and so far the side cameras have failed - condensation in the headlamps, and now this. Come on BMW - I know nothing is perfect, but really?

Originally Posted by M4apex

I didn’t find much on the F8x forums about this problem and the fix, so I wanted to share my experience and fix.

About a week ago I noticed that my radiator fan started running at full blast all the time, even when cold starting in the morning. When stopped at a red light, I could also hear the fan vary a lot in speed, which was weird. I checked coolant reservoir and all was ok.

Since my 10k miles service was already scheduled (for today), I just waited until I brought it in. At first they thought it was a water pump problem (I did read online that a constantly running radiator fan is a possible indicator of a soon-to-fail water pump), but they confirmed all was ok with the pump and no leaks in coolant system. Hmmm.

Then they checked the A/C system. According to my SA, BMW sometimes over-charges the system from the factory?? Sure enough, my system was over charged. BMW spec is 550gr, and my system was at 649gr. They re-charged the A/C system to the correct factory spec of 550 gr. This appears to have fixed the always-on fan problem. I’ve only driven it about 20 miles since picking it up from service, but the fan is not running constantly anymore.

I'll keep on eye on this to make sure the A/C over charge was the culprit, but just wanted to share with everyone.

Has anyone else had this fan-always-on issue, and the fix was A/C over charged?

[nicknaz]

Are you guys sure it is an "issue"? I always interpreted it to be a designed feature, namely the massive cooling capacity of the car that keeps oil temps in check even in 100F ambient temps at the track.

Another thing to keep in mind is that sport+ seems to turn the fan on more, because the oil temperature is kept lower than in sport or efficiency throttle mode.

Good luck OP with your AC fix.

That said I think if the car is not overheating and the AC is blasting cold air, call it normal and just enjoy the car.

[M4apex]

Originally Posted by nicknaz

Are you guys sure it is an "issue"? I always interpreted it to be a designed feature, namely the massive cooling capacity of the car that keeps oil temps in check even in 100F ambient temps at the track.

Another thing to keep in mind is that sport+ seems to turn the fan on more, because the oil temperature is kept lower than in sport or efficiency throttle mode.

Good luck OP with your AC fix.

That said I think if the car is not overheating and the AC is blasting cold air, call it normal and just enjoy the car.

Agreed that it does have massive cooling capability.... a great thing! After and during reasonably aggressive canyon driving in the summer, I would definitely hear the fan, as designed.

But, I would never hear the fan immediately after cold start in the morning, esp during 10F-20F winter weather. And I have had the M4 for about 9 mths, and 10,000 miles of driving. So the sudden full high speed of the radiator fan upon cold start really stood out to me. And the constantly varying speed of the fan, from high to low, back to high, etc. It just started suddenly a few weeks ago.

Dealer diagnosed as a failed a/c compressor. They installed the new compressor on Thursday, but then broke the tabs on re-installing one of the intakes when putting it all back together. I'm yet again waiting for a part from Germany. I should have the M4 back in a week or two. I'm anxious to see if the a/c compressor was really the culprit.

[mazaa93]

Originally Posted by racerblade

I've got the same issue - taking it in to the dealer tomorrow. Amazing that this thing only 8K miles on it, and so far the side cameras have failed - condensation in the headlamps, and now this. Come on BMW - I know nothing is perfect, but really?

My M4 is arriving in about 2 months... This is NOT what I wanted to read.

Actually worried now lol.

[forza1976]

Originally Posted by mazaa93

My M4 is arriving in about 2 months... This is NOT what I wanted to read.

Actually worried now lol.

Then you worry too much. There are 5 others (including myself) here in Denver that are not experiencing this issue. There are hundreds if not thousands on this board also not experiencing this issue so that should help you rest easier.

Unfortunately for Chris, he is experiencing it but it will get solved.

[mazaa93]

Originally Posted by forza1976

Then you worry too much. There are 5 others (including myself) here in Denver that are not experiencing this issue. There are hundreds if not thousands on this board also not experiencing this issue so that should help you rest easier.

Unfortunately for Chris, he is experiencing it but it will get solved.

You've just given me some peace of mind then, guess Chris just got a bit of bad luck with his.

[M4apex]

I finally got my M4 back after 18 days at the dealer, waiting on parts from Germany. M4 seems back to normal, but I've only driven about 200 miles so far. The a/c condenser had a leak (caused by the failed pressure sensor) which was causing the radiator fan running on high/varied speeds all the time. They replaced the condenser and a/c pressure sensor, and all seems ok.

And in my earlier post, I mentioned it was the a/c compressor that failed. My bad. I simply misread the tech's notes, and probably didn't listen too closely to my SA. It was always the condenser.

So, life returns to normal with my M4. I had an X4 28i loaner for the 18 days. It was nice and all, but WOW, did I miss my M4!!! Makes you truly appreciate the M4!!!

[Craigito]

I'm having this exact issue. First AC died. Then noticed the engine fan starting and stopping even when cold. Dropping off car Monday. 2016 M4 F82

[4everkidd]

Originally Posted by M4apex

yup... annoying!!

Quick update... a/c pressure sensor failed. Easy fix, but that caused over pressure condition in a/c system, which caused a/c compressor to fail. This apparently causes radiator fan to run on high with varying speeds, which is my symptom. Compressor is not in stock in US, so they are ordering from Germany, 2-3 weeks. At least its February and cold out! And bonus!!... they washed the M4, so saved me the time this weekend. I'll post an update after the new sensor and compressor are installed.

I've got the same issue; fan constantly on with varying speed. Also my car is constantly throwing a code for AC pressure. I will have my local BMW take a look as my AC is not working and its starting to get hot here.

Thanks for posting

[aboulfad]

Funny, mine is behaving different than before, but I use S+ all the time, and I think the fans are supposed to kick to keep the engine cooler. But I did notice a different behaviour when I started using the AC... will keep an eye. Thanks OP.
Can't believe your car was at the dealer for 18days!!!

[horsepower_and_hounds]

Sport + the fan runs 24/7 also..... supports the increased track cooling capacity

[smove]

I had the exact same problem with my X5, NO coolant loss , No HI temperature NO warning, just a loud fan... Long story short took it to a the CROOKS at Momentum BMW Houston and they "said" (claimed) they changes the water pump the thermostat and couple more things. thousands of dollars and the actual fix was as simple as you said because the AC was overcharged... That's why i said lucky you, you got a conscientious dealer/service person.

[Race_Doc11]

I think I have the same problem. Car is brand new with less than 200 miles on it.

[MNoob]

Originally Posted by Race_Doc11

I think I have the same problem. Car is brand new with less than 200 miles on it.

My car just started doing the exact same thing as in the OP video. And the AC don't blow cold.

[SOLIDM4]

Originally Posted by M4apex

I didn’t find much on the F8x forums about this problem and the fix, so I wanted to share my experience and fix.

About a week ago I noticed that my radiator fan started running at full blast all the time, even when cold starting in the morning. When stopped at a red light, I could also hear the fan vary a lot in speed, which was weird. I checked coolant reservoir and all was ok.

Since my 10k miles service was already scheduled (for today), I just waited until I brought it in. At first they thought it was a water pump problem (I did read online that a constantly running radiator fan is a possible indicator of a soon-to-fail water pump), but they confirmed all was ok with the pump and no leaks in coolant system. Hmmm.

Then they checked the A/C system. According to my SA, BMW sometimes over-charges the system from the factory?? Sure enough, my system was over charged. BMW spec is 550gr, and my system was at 649gr. They re-charged the A/C system to the correct factory spec of 550 gr. This appears to have fixed the always-on fan problem. I’ve only driven it about 20 miles since picking it up from service, but the fan is not running constantly anymore.

I'll keep on eye on this to make sure the A/C over charge was the culprit, but just wanted to share with everyone.

Has anyone else had this fan-always-on issue, and the fix was A/C over charged?

After I installed my DP's I started hearing my the fans constantly running but I was told because of all that heat and straight pipe, this is common. correct me if I'm wrong. but makes sense to me.