Car making a hissing or sometimes a low humming noise while driving coming from Left side of engine. Have had it checked out by local mechanic who and can't figure out what it is. Makes me nervous as it is getting worse at higher speeds on Freeway. (Note: it has 272K miles on it)
@monti-ji
you probably have a vacuum leak, all the hoses get loose, the clamp gets too old it doesnt hold on tight enough. you need to find where the noise is coming from., make sure your oxygen sensor is tight enough and always use anti-seize cream to prevent corrosion and prevent from metals bonding because of heat. the noise could also be a fuel injector seal gone bad, bad manifold gasket. maybe injector is stuck open?
It could be an exhaust leak. Check the manifolds and connections on the exhaust.
