2016 Mustang GT 5.0 with 13500 miles. After having evaporator core replace along with an oil change, I noticed a deep tapping noise coming from my engine. My first response was to check the oil to make sure they filled the oil. After verifying oil was fine, I thought it may be something grounding out, or maybe something got moved during their attempt to find the ac leak. I could not see anything rubbing or grounding out on anything. I could easily reproduce while in park and getting the RPM up to about 1200 to 1700. Sounding like someone with a hammer pounding on my engine.

I finally took it to the dealer where they said we hear it but I can't find the location of the noise. Everyone at the dealer said it was not a normal noise. Three days later, they tell me per SSM 49761 its normal characteristic of the engine after an oil change and detrimental to the engine. Ford told them to compare to multiple like cars until they hear a similar noise "so they can tell the customer its normal", then the dealer told me they have no similar vehicles in service at this time, so I should pick it up and drive it for 500 miles to see if noise goes away... if not, use rabbit ears to try to determine noise location.