Hello, first thank you for your time. I have a 2002 Pontiac Grand AM GT with 151,000 miles (I have had the car for 6,000). I recently just changed the oil with 5w-30 which is the 3rd oil change I have done and have used the same brand and viscosity. It seems the oil is a little overfilled this time (maybe 1/4-1/3 of an extra quart). I noticed a knocking coming from the engine (closer to bottom of engine than top) on a cold start. It sounds like a rock being knocked against a hard surface. I can only hear the knocking if I am outside of the car, if I am in the car I can’t hear it at all. The knocking lasts for maybe 20-30 seconds. If I press the accelerator (when in park) the knocking goes away, and if I let off the accelerator then it comes back. I can’t really test to see if the knocking persists while driving since I can’t hear it from the cab.
I know I should do all the routine maintenance when getting a used car (spark plugs, etc), but I bought from a friend who put spark plugs on maybe 25,000 miles ago.
I read that maybe I should be using different viscosity of oil in the summer (even though the manual says 5w-30 all year, I live in North Central Nebraska)? Is the knocking maybe due to the slightly overfilled oil? Should I try to drain that excess out? Should I just go ahead and replace the spark plugs and wires as well?
I drive ~750 highway miles a month and hope I can get this car to last a few years. So far it seems pretty good, have only had to change the ECT sensor and thermostat on it, suspension bushings still look good. I just never heard this noise before and it kind of freaked me out. I probably would have never heard it but I just happen to start the car and needed to grab something from the garage.