Blowing exhaust??

[gti69]

When i first start my car after it has been standing for a while it sounds like a tank! It sounds as if the exhaust is blowing (a full magnex system, using standard manifold), however once the car has been running for a while it is a lot quieter.

Any one got any ideas as it is driving me mad!

Thanks

[Bdub]

You obviously have a leak somewhere which is closing up when it gets hot. Check your joints, particularly where the manifold meets the head and where it meets the down pipe. There could also be a crack int manifold itself - I have tried welding manifolds in the past but as they are cast it's not very successful.

Start the car from cold and get your ears and hands round the joints before they get too hot - you only have a few seconds though so be careful.

Usually the louder the noise the closer to the cylinder head it is.

It could also be loose baffles in the exhaust but if it's a new system I doubt this.

See how you get on.

[gti69]

I took it to an exhaust specialist fairly recently and they couldn't find anything wrong with it! They did all the leak checks but as far as know didn't check the manifold.

When i get home form work i will do a bit of investigation. If it is the manifold it will be just the excuse i need to buy a TSR stainless manifold!

Thanks Bdub

[richandhazel]

Hi Bdub,
do you or anyone else have any suggestions on repairing exhaust manifolds?
I have one of the lugs broken off, on one I want to fit to replace my 4 into 1 and realised, like you, that as its cast, it isn't going to weld.
Not having a lot of luck in sourcing another 4 into 2 manifold  

You obviously have a leak somewhere which is closing up when it gets hot. Check your joints, particularly where the manifold meets the head and where it meets the down pipe. There could also be a crack int manifold itself - I have tried welding manifolds in the past but as they are cast it's not very successful.

Start the car from cold and get your ears and hands round the joints before they get too hot - you only have a few seconds though so be careful.

Usually the louder the noise the closer to the cylinder head it is.

It could also be loose baffles in the exhaust but if it's a new system I doubt this.

See how you get on.

[Bdub]

It can be done using cast rods on an arc welder but the whole thing needs to go in a oven at 650 degC for 1 hour afterwards to relieve the welding stresses.

You need a good welder though - I personally would try and source a new manifold or get one fabricated.

Sorry not much help.

[richandhazel]

It can be done using cast rods on an arc welder but the whole thing needs to go in a oven at 650 degC for 1 hour afterwards to relieve the welding stresses.

You need a good welder though - I personally would try and source a new manifold or get one fabricated.

Sorry not much help.

I was afraid of that but you've confirmed what I thought...........Oh well I'll keep looking..........