John,
The first place I would check is the joint between the exhaust manifold and the
downpipe. There is supposed to be a copper gasket that fits in this joint,
but these tend to go with monotonous regularity. They are cheap, and
reasonably easy to replace, but you do get fed up with it when you are doing
it every other month...
I have had advice that if you ensure both mating surfaces are very smooth, then
they go less often. I have a simpler solution - just forget the gasket and do
it all up without. I had to put a thick washer under the nut, as the threaded
section was too short to allow the nut to do up fully without the gasket
acting as a separator between the manifold and downpipe.
Hold it, didn't you say a couple of postings ago that you just fitted a S/S
header? Am I right in thinking that you don't use a gasket with these? Well,
I guess that rules that out. Have you had this noise since you fitted the
header? If not, how soon after did it appear? Could it be the nuts holding
the header on were not tight enough, or have worked loose? Did you manage to
get all the nuts back on again - some of them are bloody awkward to get to.
Did you fit a new manifold gasket when fitting the new header?
Just a few thoughts, maybe one of them will help!
Richard and Daffy
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