[Roadsters] exhaust manifold leak

[Paul Strahl]

Hey I have owned my 1970 1600 for almost a year now. No known modifications.
It 
has been running great until just now. It became really loud. I had a
muffler 
shop look at it a replace a pipe just before the muffler. It sounds
like normal 
now. The muffler shop guy called to my attention that the
exhast mainfold had a 
leak and he would have to take it apart to see if it
was a gasket, crack, 
warping or what was going on. So I have a couple
questions for the guys who run 
these cars and know about them. 1) How can one
tell the that the manifold leaks 
and where it is leaking? 2) Is this a common
problem 3) What are common 
solutions?

Thanks in advance.
Paul S