tehsteve86 Posted January 12, 2016 Share Posted January 12, 2016 Morning! Past few days my 2011 BMW 335xi has been producing some weird sound coming from the engine bay. I decided to drive it a few more days to get more detail on how to replicate the sound. a "dentist drill" noise is audible, The sound gets louder as I apply slight revs for normal driving & and small revs on idle. However, the frequency of the noise is constant between 1.5krpm & 5k rpm. doesn't appear on a cold start, but as the oil gauge in the car becomes normal temp, the "drilling noise" becomes constant & as I apply revs it gets louder. on a cold start you don't hear it, but it becomes quite audible as the car warms up to normal operating temperate no CEL code on the car. Haven't boosted due to the fact if it is my turbo, I don't want it flying into my engine bay. Haven't noticed any power loss, but then again, I am bumper to bumper to and from work. Don't notice any blue smoke coming out of tailpipes. Here is a video of the issue: http://sysadminsteve.com/help/issue.mp4 At first I thought it was the belts or the pulley bearings. Now, I am not so sure since I noticed this happens when oil becomes normal operating temperature. Bad oil pump. Turbo going bad? Link to comment Share on other sites More sharing options...
DoctorD Posted January 12, 2016 Share Posted January 12, 2016 (edited) Serpentine Belt or a bad pulley(usually the tensioner pulley) also check your power steering fluid. Edited January 12, 2016 by DoctorD Link to comment Share on other sites More sharing options...
tehsteve86 Posted January 12, 2016 Author Share Posted January 12, 2016 Thank you, I will double check my fluids when I come home from work today. I need to top off my window washer fluid anyway. If it is the belt or pulley, do you think I can drive it till Saturday? I have a good feeling I already know why you ruled out the turbo. Link to comment Share on other sites More sharing options...
sc302 Veteran Posted January 12, 2016 Veteran Share Posted January 12, 2016 Yea you are fine. Just beginning to wear. How many miles? The belt should be replaced at around 100k-120k. Idler, when it starts making noise...Could be 100k could be 500k. Could be idler, could be any other pulley. Def something in there. A stethoscope could help identify where noise is coming from. About 10 bux from Pep boys. Link to comment Share on other sites More sharing options...
xendrome Posted January 12, 2016 Share Posted January 12, 2016 Could even be a vacuum hose leak? Link to comment Share on other sites More sharing options...
tehsteve86 Posted January 12, 2016 Author Share Posted January 12, 2016 (edited) I am at 30k miles. Purchased used @ 12k and it's been running fine since. I quickly ran out and checked my PS fluid. It seems very low, but I haven't driven it in 6 hours. I'll check the level when I get home to incorporate fluid expansion lvls. In the reservoir itself, I see what looks like to be plenty of fluid. However, the plastic crappy dipstick that comes with the car. It is not sitting in between the marks. I read that the caps are crappy for BMW & I do see some residue around the area. I'll clean it off. Edited January 12, 2016 by tehsteve86 Link to comment Share on other sites More sharing options...
sc302 Veteran Posted January 12, 2016 Veteran Share Posted January 12, 2016 At that mileage you may still be under warranty. I would have it checked at open road bmw. Link to comment Share on other sites More sharing options...
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