bmwlexus09

I had my car serviced in March and since I picked up my car, I’ve noticed a dripping or thumping sound when I brake from about 40 mph. At first I thought it was because of rain drop hitting the roof because it sounds like a big drop of water hitting the roof. And just one drip or thumping sound each time. Sometimes the sound is faint and other times it’s fairly loud. But it does not happen all the time. Any thoughts on what is causing this sound?

arentz07

Can you describe where the sound is coming from? Is it actually coming from the roof/headliner? What you're describing sounds like it could be the exhaust pop sound that I and some other members have experienced - except that sound comes from below the car.

pngo

Is there anything in your trunk or glove compartment that could be rolling around?

bmwlexus09

It sounds like one (just one) large drop of water hitting the roof. I hear it on the right side of the car. The sound sometimes is very faint. I’ve noticed it happening sometimes when I brake for turning but it happens when I brake harder than usual. And it’s just one drip or thump sound. Never multiple drips or thumping sound.

I don’t have anything rolling around in the car, arm rest, trunk or anywhere else in the car.

arentz07

When you say it's just one thump sound, I definitely think it sounds like the exhaust pop. Maybe try checking underneath the car for damage to the exhaust system. If the previous owner (or, you? ) ran over an object, it could have messed with the position of the exhaust, causing it to slap the underbody in some situations.

mcomer

Object in the sunroof track perhaps?

bmwlexus09

I’ve narrowed it down to the sound coming from above the driver seat. It sounds like it’s coming from the roof. It’s happening more frequently now, just not all the time. But my moonroof operates normal. I’ve only open and closed it less than a handful of times. Never had this problem before March.

Checked my exhaust system and no damages there. Had deep engine clean twice in the past two years due to carbon build up per service adviser even though I’m only at 30k. I mention this because the reason why I dropped off the car for service it was because the rpm dropped to 300~400 and the exhaust sounded like it “farted”. So I know when the exhaust acts up.

bmwlexus09

Update - went back to dealership multiple times and service advisor test drove the vehicle with me. Long story short, the technician replaced the sunroof accordion, replaced the sunroof seal, and added insulation. The car drives like night and day difference. No noise now. Hope this knowledge helps someone else.