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BMW And MINI – Engine Noise At Idle – Chirping

April 7, 2011

I purchased a 1998 528i 2 1/2 months ago with 164,000 miles. I was told it was maintained very well, including servicing at Motorwerks BMW, (a dealership in the twin cities) oil changes using synthetic oil, and fueling with 92 octane fuel. This is the first BMW we have owned, and my wife and I really enjoy driving it. Recently I began to notice a different sound at certain times. I would describe it as a semi-high pitched rhythmic whine coming from the engine while the car is idling in either D or R. It almost sounds like a quite loud cricket continually chirping. When you step on the accelerator it seems to stop, and if you shift the car into P, it becomes faint enough to almost be difficult to hear. My question is do you feel it is something I should try to alleviate with the products such as Lubro Moly cleaners and protectants, or do you think it is maybe a matter of bringing it to a mechanic to look into having the belts or other equipment replaced. I am not sure if this can be viewed as normal for a vehicle with 164K miles, or if it may be an indicator of something more serious that should be addressed to avoid causing damage. The performance doesn’t appear to be hampered in any way. The car gets good gas mileage, has great pickup especially at highway speeds, and idles smooth.

At this point, we are unable to make a solid suggestion on what the chirping sound may be. Our first thoughts would be the serpentine accessory drive belt and the idler and tensioner pulleys … or …. a vacuum leak in one of the intake or crankcase ventilation boots, bellows or hoses. However, we would suggest some initial diagnostics. Use a mechanic’s stethoscope with a megaphone attachment for locating airborne sounds. While the sound is present, search around the engine compartment (assuming that the sound is coming from under the hood) for the general area of the sound. Then, try to get more detailed. At this point, concentrate on the frontal area where the accessory drive belts and the pulleys are as well as the various air hoses around the intake manifold.  Let us know what you find.

stethoscope kit:


  1. wayne permalink

    I’ll tell you right now it’s your idler pullry. I had the same thing happen to ne, and the mechanic couldn’t tell me what was wrong. 1000 miles and 1300 dollars later on the highway at 0300 in the morning no less. So change the pulley it’s less than a hundred bucks and you’ll save replacing tensioner, idle pulley,belts, expansion tank, thermostat, and some hydrolic or other. They call it complete hydrolic. And they charged me for antifreeze and when I got home the expansion tank was empty. And they may want to change your water pump same time. Don’t forget they also charge 105 dollars and hour. I was in S carolina 8 hours from my home so I basically was out of options. Some of the things listed I have no idea why they were needed. So think about my 1300 bucks when you start that car next time, grin and have the mechanic replace the idler pulley. I think the bushing in the pulley wears and causes the wheel to make a noise because it’s loose (I’m no mechanic) That’s why it’s only there when the car is under load at low revs.

  2. Joshua Sanders permalink

    You are closely describing the scenario I was dealing with last summer (2010). My 1998 528i was “chirping” loudly while in any drive gear. This was very annoying during stops, and I found that if I put my car in Neutral, the sound would stop almost completely. My first concern was that the water pump bearing was failing. Not knowing if it had been replaced by the original owner, I ordered a new water pump, idler pulley, belts, thermostat, aluminum thermostat housing, coolant hoses and some other maintenance items from BavAuto (my care had just over 100K when I was experiencing this). While removing the accessory belt, I heard a familiar sound come from the mechanical (spring loaded) belt tensioner. I removed the belt and started quickly actuating the tensioner, and wouldn’t you know it? That was the culprit for the sound. I went ahead and replaced everything that I had purchased and buttoned everything up. I ordered my tensioner that evening and replaced it several days later: “Chirping” sound gone! The mechanical tensioner can wear out over time and vibrate excessively while the engine is under load. Putting the vehicle in Park or Neutral reduces the load on the tensioner, which usually quiets it down. I recommend replacing the idler pulley, as well. The bearings on these can start making noise, also. It’s cheap and you’ll have the belt off doing the tensioner, anyway. Good luck!


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