What Causes an Exhaust Manifold to Crackor Leak
Your car has two manifolds – an
intake manifold and an exhaust manifold. Both serve essential purposes,
but the one most likely to experience problems over the long term is the
exhaust manifold. Depending on your make and model, your manifold might
be a single piece of cast iron with channels/ports built into it, or it
could be a collection of pipes tied together. The basic job of the
exhaust manifold is to take the gases from each cylinder and send them
to the exhaust pipe.
Why manifolds crack and leak
As you can imagine, exhaust
manifolds are subject to intense heat. They're also subjected to
considerable expansion and contraction as they heat up and cool back
down. Over time, this leads to metal fatigue (both cast iron and other
types of exhaust manifolds are subject to this). As the fatigue becomes
worse, it's possible for the manifold to develop cracks.
Another potential problem lies with
the exhaust manifold gasket. The gasket sits between the manifold and
the engine block, and is designed to seal the small gap that exists
between these two components. Like the manifold itself, the gasket is
subjected to significant heat, as well as expansion and contraction. It
will eventually fail (this is normal, and cause by nothing more than
general wear and tear). When it fails, it will begin to leak.
Problems associated with manifold cracks and leaks
There are several problems created
with exhaust manifold cracks and leaks. First, hot exhaust gases are now
being vented under the hood, rather than being sent downstream through
the exhaust pipe. This can damage plastic components in the engine bay.
It can also become a health hazard, as the exhaust fumes can enter the
car's cabin.
There's also the possibility that it
will affect engine performance. If your exhaust manifold is cracked or
leaking, the back pressure in the exhaust system will be incorrect,
which can reduce engine power, cause sputtering and other problems. Of
course, you won't pass emissions testing, either.
