Exhaust manifold repair?

[e...@uxh.cso.uiuc.edu]

I own a 1975 vehicle with a cracked exhaust manifold. I'm told that
replacing the manifold could be quite expensive because on a car of
that age, it is common for bolts or studs to break off when the old
manifold is being removed. When this happens, the old bolts must be
drilled out, etc., which may mean pulling the head and, to make a
long story short, may result in many additional hours of labor.

What I'm wondering is... Is it possible to have the crack in the
manifold welded without removing it from the engine? Or is there any
other cheaper approach? (I tried sealing the crack with a product
called "JB Weld" which claims to work for such things, but after a
few hours of operation, there wasn't a trace of it left, even though
I followed the directions. I didn't really expect it to work.)

Bill Entwistle e...@uxh.cso.uiuc.edu

[David Hebert]

Exhaust manifolds can be repaired by heli arc welding. I have had this
done, but never with the manifold still on the car. I have pulled many
exhaust manifolds on many different cars without screwing up the exhaust
manifold mounting bolts. You may need to use a lot of penetrating oil
(such as liquid wrench) and a rubber mallet to get the bolts/nuts
off and the manifold off of the cylinder head.

I suspect that any "cold" patch that may be claimed as a fix for
such things just won't work. They are probably polymer based and can't
withstand the high temperatures experienced by the exhaust manifold.
Such sealants might work OK on a cracked intake manifold where the
because the intake manifold temperature is much lower.