boomy sounds

[Diluxe]

when i start my car in the morning the engine noise is very boomy and just drones infact it sometimes drowns out the radio, as she gets warmer the quieter she gets, at 90C plus, she's purring like a normal car, the drone is definitely coming for the front of the car rather than blown back box style,

any ideas?

cheers

[Brads MK2 GTI]

Could it be your exhaust manifold? Maybe when the air get's warmer it changes pitch

[s3akr]

Mines the total opposite - quiet when cold, boomy when warm!  Mine is a leak at the gasket where the manifold and downpipe join. When I can be arsed I'll fit the new gasket I've had for nearly 4 months!

[Diluxe]

i feared that maybe the exhaust manifold gasket might have gone, and when warm it expands and fills the gap and thus car get quiter, how hard is it to replace this gasket, should i take that inlet manifold off to get to the bolts, does the subframe need to be dropped?

[rubjonny]

not easy at all, if you take the driveshaft heat shield off you can get to 5 of the bolts, but the last one is a right mare to get to!  You'll probably end up shearing off most of them too

Worst case you'll have to take the manifold off, which is only possible really once you take the inlet off.  Get some decent mole grips before you start, as at least one of your manifold studs is gonna round off!  Good luck, you're going to need it

Before you start though, run it from cold with the bonnet open to see if you can track down where the sound is coming from, hold your hand around the joint to double check its actually leaking!