Greetings, this is my first post in these forums after a couple of years of membership. I own a '99 E36 M3 and an '03 540i M-Sport Touring. My M3 has had "crickets" or chirping for quite some time, I assumed at 95K I just needed to replace the original deflector, pulleys and tensioners and the noise would go away. Sadly, after replacing those parts the crickets are still there. The belts are maybe 2 years old with less than 10K miles and do not have cracks in them. The water pump is about 3 years old with about 10K miles on it, the alternator is original. Here are some patterns/info I've discovered -Having AC on or off does not seem to make a difference. -The sound never happens at rest while revving the engine, only while driving. Which of course makes it really hard to determine where the noise is coming from. -The sound is not constant, but it seems to occur only as the revs pass between 2,000 to about 2,500 RPM, which is typically fairly quick so it's just a little chirp or 'cricket' sound. 2nd gear is pretty consistent, 4th gear seems to really bring it out, perhaps because it passes through the revs a little slower in that gear. Sometimes in fourth gear holding at just the right RPM, a little over 2K, I can get it to continue constantly. Heading out to Mid-Ohio for CCA HPDE in a few weeks, 10 hour drive to get there, want some piece of mind! Just looking for possible direction/ideas. Alternator? VANOS? Thanks!
Noises a very hard to diag over the internet. Is there any way for you to record the noise for me to hear? To start need to eliminate if it an accessory on the engine i.e. alternator water pump, belts like you mentioned. Best way to do this is to remove the belts and fan of course and drive the vehicle and listen for the noise. CAUTION with no belts and fan means the water pump will not spin and the fan can not cool meaning the engine will over heat DO NOT drive to long like this just enough to see if the noise is gone. If the noise is gone then it is one of the items that is belt driven. If it is still there then further location of the noise will need to be done of where the noise is coming from i.e. engine, trans, driveshaft, diff.
Thanks much for the guidance. I removed the two belts one at a time and drove the car, sound still there. I got creative and zip-tied my iPhone to my strut brace to capture the sound as I drove. Here’s a link to the audio file: https://www.dropbox.com/s/z9soiasijijgrsz/M3Crickets.m4a?dl=0 The best examples are about 1:01 and 1:18 points, but here is a list of occurrences in the audio file: :27 :36 :40 :42 :45 :47 :58 1:01 1:18 I appreciate the help.
The audio clip had quite a bit on interference noise so not sure I picked up exactly on the noise you are speaking of. Side note exhaust sounds really nice! Were you able to locate the noise down to a area such as the engine or trans? Does the noise happen every time weather the engine is hot or cold?
Thanks, super sprint exhaust with active autowerk cia. It happens hot or cold. Pretty sure it is coming from the engine. Right at about 1:18 is the best example of it, it is a high-pitched squeal, subtle but you can hear it through the other noise. Might be harder to pick up on a phone. Thanks again for the guidance.
My indy mechanic diagnosed the sound as air whistling somewhere in the cai tube/throttle body. He said he has seen this before and it does not mean there is a leak, just an anomaly caused by the increased air flow of the cai. It turns out it is possible to invoke the sound at rest after all. I removed the air filter and the sound seemed more pronounced so his diagnosis seems logical to me. Unfortunately it's something I have to live with but at least nothing is wrong!
Sorry did not know you had a cold air intake on the vehicle. Yes I had one on my vehicle it also to make noises at certain RPM's. Glad you found out what it was.
