Fairly loud BOOM from under car on way into work
 

I had just made a downward slope sharp turn at a set of lights this morning, going maybe 25-30 mph, when there was a loud and hollow BOOM from under the car, to the rear. Think empty oil drum being hit with a rubber hammer.

I pulled over, nothing obvious wrong, nothing leaking or hanging off. No debris on road to indicate I had run over something.

Rest of drive was fine. I deliberately tried to mimic the turn, and drove over bad sections of road, no more sound.

It reminds me of the sound I got once from a car where the parking brake was seized on from sitting and I drove it back and forth to force it free. Similar hollow boom when it let go.

The exhaust is brand new (10 days). We inspected the flex discs when we did the exhaust and they looked great.

I am about to replace the driveshaft center bearing, as I had a whine at cold temps last winter. But I can't imagine how that could make such a noise then continue to turn....

Thoughts anyone?

Revisit the last work that was done to the car.

If its one of the vehicles in your sig, maybe an exhaust hanger or sway bar link?

Only guessing because only way is to put her up on hoist or crawl under. But I once had a loud noise on my R107. One of the sway bar links had come undone and had caught on something.

Hope its nothing serious.

fuel tank?

DOH. Sorry, it's the '85 300d.

I am wondering if either the new muffler or resonator failed internally.

Fuel tank... had not thought of that. And I seem to remember a post from someone who had a similar issue, long time ago....

Something like a sway bar link falling off would be plausible, Graham, given the noise, however if it was left on the road I missed it (I walked back to check for debris, etc.). And it handled normally rest of drive (I have to negotiate two traffic circles - roundabouts - after that point, which load the suspension, to get to my office).

Check your front sway bar connections and the plastic rear sway links, one of them could have blown apart. I've seen it happen on two of our cars....especially in places with winter weather.

Could also have been a spring coil snapping, does the car sit level/springs look good?

Spring very plausible based on the sound, PawoSD. Your idea just reminded me that I had been hearing a dull rubbing sound, not loud, lately from the right rear when turning left. So far I had filed it in the "misc whassat?" folder in my brain.

However, the boom was immediately after a sharp left, downhill, and I had to go around two traffic circles in a left arc immediately after, and no sound. I would expect a broken spring to show up going round a traffic circle, no?

The car seems to be sitting fine.

tank?
 

I second phillytwotank. It's only four 8mm hex screws to remove the fuel tank partition and have a peek. Or get under there and shake the muffler to see if it comes into contact with anything since thats the last work you did. Hell, it could have been cargo sliding around in your trunk.

No, this was a BOOM not a bang or a thump from the trunk. There is nothing in the trunk remotely capable of making the sound I heard, trust me.

I was genuinely surprised the car still ran and drove after. Sounds like that tend to attract flatbeds.

Roadside IED?

These cars are made like tanks, after all. May have just saved your life!

[QUOTE=Zacharias;3326624]No, this was a BOOM not a bang or a thump from the trunk. There is nothing in the trunk remotely capable of making the sound I heard, trust me.QUOTE]

I just wanted to make sure we rule out the simple things first :)

Failed car bomb attempt?

Have you pissed off anyone recently?

Would you like the list alphabetical or by nature of offense?

You and uberwasser should hit the comedy circuit :D....

Busted!

Someone didn't read through the whole thread and he thought he was being so unique!

Sorry Uberwasser - you have it.