Hello all,
I have a 2005 MCS with about 113K miles. Lately I have been hearing a knocking noise intermittently under acceleration. When driving today up a steeper hill my rpm dropped to about 1,500 and i heard the noise. In order to test the noise again I accelerated heavier to about 4,000 rpm in 3rd gear and heard the noise and vibration again. It is hard to describe the noise, but have ruled out the possibility of it being the “death rattle”, as my sound is more so like a deeper hollow knock and not clicking. The car does not do it frequently or even all the time under the same conditions. Their used to be a similar knocking noise that was just solved by replacing the upper engine mount, so I am wondering what this could be. I have noticed the driver side (left) CV boot has been torn and there is grease everywhere. I know this may cause vibration but could it also create noise?
Thank you in advance for any help and suggestions.

 

Does it come through on video? (hard to say with so little detail)

Are you saying you can’t reproduce the noise consistently?

 

I know, it is hard to describe. I can try to take a video but I feel as if it may not be noticed in a video.

And yes, I cannot reproduce it consistently.

 

With a torn CV boot you're obviously losing grease at the axle. Over time that would wear on the axle bearings which could be the noise's source, particularly under acceleration.