thump thump noise

when i start my car after sitting all night i can hear a thump thump noise in the rear of car ,its only when i first start it anybody ?

Don't worry mine does it too,,its just a bit of air in the muffler system 'burping' out...nothing to worry about..

HuH? Air in the muffler ? Wouldnt that be exhaust?..

the muffler is part of the exhaust. what did you think it was part of - the window?

sorry to you all, its the gas tank vent opening up to release preasure:grinyes:

it makes that much noise to vent? weird

Thank You for that,Hmmm,I guess The rear of the car would be a "NO SMOKEING ZONE" Ha Ha:lol: >>>>>>:smokin:

I think the thumping noise is related to the emission system.

On my car it happens at exactly the same time after a cold start and it thumps the same number of times. I don't pay much attetion to it any more, but I think it's 40 seconds after engine start and 5 thumps. It doe this every cold start since the car was new.

I figured it's the electronic engine control testing the EGR valve, but that just a SWAG on my part.

I TEND TO BELIEVE
greger691982 (http://www.automotiveforums.com/vbulletin/member.php?u=508886) ... MAKES SENSE TO ME .. WHAT IS SWAG ?

I Counted My Thumps At 20 .....