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01-22-2024, 07:00 PM | #1 |
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Help! Weird rattling noise from the engine bay. Car runs just fine
2009 /E70/X5/ 4.8i with around 110k miles
This has been bothering me for almost an year. Bought a Mechanics Stethoscope from HFT , tried to probe where the noise is coming from. It sounded like it was coming from or near the thermostat, so I went ahead and replaced the thermostat. Replaced water pump also while I was there. Car was due for a coolant flush anyway. But that didn't fix the noise. https://www.youtube.com/shorts/HUic0eX1ZAo Please listen to the YouTube short and feel free to chime in. All kinds of guesses are welcome too!
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01-22-2024, 07:05 PM | #2 |
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Pull the accessory belts off one-by-one and see if the noise goes away. Could be a pulley, but it also kinda sounds like the fan is hitting the shroud. Are there any loose pieces floating around in the fan shroud?
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01-23-2024, 09:56 PM | #5 | |
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However, good point though. I will try it one more time after a 30 minutes drive, so the engine is at normal op temp and the sound comes on on idea also btw, no loose items near the fan and also its absolutely silent on cold start. I forgot to mention that
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01-23-2024, 09:57 PM | #6 |
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no, nothing hits fan. checked that. Thanks for the suggestion!
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01-23-2024, 10:02 PM | #7 |
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Thanks for the suggestion! Will try that if nothing else makes sense. I forgot to mention that it doesn't happen on cold start, but only when the engine reaches normal operating temperature, which lead me to replace the thermostat. I thought it comes on when the thermostat opens up and the coolant start to circulate.
If it is the belt tensioner, it should start the rattling on cold start also correct ?
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01-23-2024, 10:05 PM | #8 | |
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Maybe try unplugging the fan when it's making the noise? |
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01-24-2024, 01:57 PM | #9 | |
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01-25-2024, 01:01 AM | #10 | |
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Well, I went ahead and disconnected the fan electrical connector, after a 20 minutes drive today. It still makes the noise without the fan running :-( Idled the car for about 5 minutes without fan and it was really mad when I connected it back. I think the temp went up without the fan running. Fan went into the high speed mode when it was reconnected with a super loud noise, blasting at full speed.
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01-25-2024, 01:04 AM | #11 |
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It's definitely in my list of items to replace, but I am looking for other possible causes before doing so. Thanks!
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