gas tank flapping noise

[rmmchl]

250 sl--- just had the gas tank relined along with my engine rebuild. When I start off slowly, I can hear a rhythmic flapping noise that sounds like it's inside the gas tank. It quits after about 10 seconds. I'm taking it back to my mechanic, but does anyone have any idea what they might have done wrong, and what the noise is?

[rwmastel]

quote:Originally posted by rmmchl

I can hear a rhythmic flapping noise that sounds like it's inside the gas tank.

Can you be more descriptive?  Flapping like a flag on a windy day?  Rhythmic as in 1 flap per second, or 10 per second?  If you start off from a stop and a person is standing next to the car, can they confirm the noise is coming from the rear?

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[rmmchl]

more like one flap per second. It's definitsly coming from the gas tank area

[Raymond]

During the ten seconds, does the frequency increase with speed?  If you go at a slow speed, can you make the flapping continuous?  Can you tell which side it's coming from?  One more silly question: did you look under the car for something stuck to a wheel?

Ray
'68 280SL 4-spd Coupe

[rmmchl]

I found out what the problem was. I failed to mention that when the tank was full it was also leaking around gas cap. I took off the screwed on filler neck cover from the inside of the trunk. When they installed the reconditioned gas tank they forgot to connect the 2 little overflow hoses that are located under this cover. I don't know what was causing the rhythmic noise I was hearing, but it's not doing it now. I also put a new gas cap filler neck rubber gasket on. A note---you must take off that inside cover to get the rubber lip to fit correctly on the body panel.