Just recently, while on a highway, there cam a loud banging engine noise from the engine compartment. It was not metal against metal or a rattle, but a banging sound, probably around sixty decibels, that lasted for about six to seven seconds. The tempo of the sound did not slow down when I deaccelerated, reflecting that the rpm of the engine nor the speed of the car was related to this condition. About five minutes later down the highway, the banging noise started again, lasting for about the same time period as the first incident. I just recently bought this car, and had put approximately 400 miles on it prior to these incidents. The banging noise started following my having some work done on my car, which was replacing the thermostat and thermostat housing/assembly, and the air conditioner's pulley. I'm afraid now to drive my car on the freeway until this is fixed. Would really appreciate some help on this.

 

you still have the stock exhaust/cat/y-pipe?
maybe heat shield rusting off and banging around?

 

Today, I am going to further examine the exhaust system and some other things. Again, thanks.

 

Might be that 400 lbs Gorilla beating his way out from underneath your hood....due to bad motor mounts!