Cooling fan not working properly?

Tiny
BHAMDOC1973
  • MEMBER
  • 2011 BMW 335
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 117,000 MILES
I have been having an issue with this car since I bought it. Drives strong. Fan always stay on high then shuts off then comes on high randomly. Usually with these cars it's a sign the pump is about to fail. Left it alone. Changed the coolant temperature sensor in the head. Nothing changed. Does not overheat. One day it gave the yellow light for temperature. So, I towed it in. No codes. Changed the pump and thermostat. Now it does not heat, stays around 220-230f if left idle for a long time. Fan still comes on while idling, at high, sometimes at low around 212 or so. Is there a relay for the fan that could be stuck? I left it running for 7 minutes and now the scanner shows 419f. Measured the radiator hoses and it's at 112 and 90f.
Friday, February 10th, 2023 AT 6:56 AM

7 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,144 POSTS
Is the HVAC system on when this happens? The reason I ask is because the fan will react to high pressure in the high side A/C compressor hose which can be the normal operation of the radiator fan. Please let me know if the HVAC system changes anything.
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Friday, February 10th, 2023 AT 11:38 AM
Tiny
BHAMDOC1973
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HVAC not on. Scanner reading 419 even when cold, hoses read 120, so reading is not correct. Wiring does not show anything about the location of the relay. Compression is perfect. No leaks. These cars only have a coolant reservoir and no radiator to too off. Bled the system 3 times with the ignition on procedure which is common.
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Friday, February 10th, 2023 AT 11:44 AM
Tiny
BHAMDOC1973
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Car is well taken care of, most BMWs have leaks and issues, this one is super clean, no oil on the bottom, compression great, I put new pump thermostat and coolant sensor, and its staying at 109c. The fan only comes on around 108 but not on high speed. Which is what I want, deleted all codes, idled for 45 minutes so far so good, when I rev it at high rpm for a bit speed of electric pump increases and coolant temperature decreases, so that is good, hoping it will stay that way. It has an aftermarket air cooler, and cold intake.
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Friday, February 10th, 2023 AT 2:06 PM
Tiny
KEN L
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That is good to hear so the problem is fixed or? So, there is one coolant sensor and if the connections are good and the scanner gives you a coolant reading of 419 that means the DME is bad, but I would check all of the fuses in the wiring diagrams below.

Here is a guide and the fan wiring diagrams so you can see how the system works:

https://www.2carpros.com/articles/how-to-check-wiring

Please let us know what you find.
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Saturday, February 11th, 2023 AT 1:19 PM
Tiny
BHAMDOC1973
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Fuses are good, tried another scanner and got the right reading between 220-230 idling.
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Saturday, February 11th, 2023 AT 1:22 PM
Tiny
BHAMDOC1973
  • MEMBER
  • 2,010 POSTS
I also found out that the car has a dang jb4, so you can actually choose for the fan to run more and more as an option so I turned that off.
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Saturday, February 11th, 2023 AT 2:35 PM
Tiny
KEN L
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Okay, good job. Use 2CarPros anytime, we are here to help. Please tell a friend.
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Sunday, February 12th, 2023 AT 1:00 PM

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