Loud tapping-like noise near #3 & #4 cylinders, exhaust side

[fletcher969]

Hi all,

 

2020 Edge SEL

 

My GF purchased this vehicle used a couple of months ago (with a dealer's 3/3000 powertrain warranty good for 3 more weeks).  At that time the engine was in the quieter range of what one would expect from an EB engine...a fluttery typewriter, or perhaps a 'soft' tapping from the high pressure fuel pump (HPFP).  About a month ago a metal rattling noise appeared overnight (most apparent during deceleration), and it had a distinctly louder metallic tone (similar to valve train noise).  After some communication including videos, we took it to the dealer, and ultimately it was identified as a failing HPFP, so that was replaced along with its roller piston.  That quieted down the overall sound level, but there was a persistent 'tapping' noise coming from the back driver's side of the engine where initially I had attempted to steer some focus with the tech who performed the aforementioned HPFP repair.  I think my observation was dismissed.  Subjectively I've felt it is getting louder, so yesterday I decided to put a stethoscope on it.  

 

Intake side is about what i'd expect for a healthy sounding valve train, and it was pretty quiet around and on the HPFP (and for the record, this engine's HPFP is driven off the intake cam...most 2.0L EB videos and pics I see show it running off the exhaust cam...not sure when that changed).  Anyway, the exhaust side was noticeably louder than the intake side starting at cylinder #1, but I attributed that to the presence of the injectors.  Cylinder #2 was slightly louder, but not alarming; however, when I got to cylinder #3 the sound was maybe twice as loud, and cylnder #4, while not as loud as #3, was considerably louder than #1 and #2.  I wish I could say the sound is metallic, but there's so much injector noise (assumed) I can't be 100% certain.

 

I listened to several other areas on the block, and if I place the stethoscope just right on the upper portion of the intake side of the block, I can hear a very faint high pitch 'ping' that seems to correlate to a single cylinder's timing sequence.  I can't get to the back/exhaust side of the block, so I can't really narrow the ping down.  Turbo, timing cover area, and lower block all sound pretty good.  

 

Question:  Is there anything in the design of this engine that would cause #3 and #4 cylinders to exhibit far louder internal sounds under the exhaust-side valve cover? 

 

Here is a link to the engine running at idle (file size was too large to attach here):  https://drive.google.com/file/d/1QP4IAkaUk_68z3KxZwLQGhBsyfpaeFzx/view?usp=sharing

 

Thanks for any input.

 

Edited for clarity

Edited 12 hours ago by fletcher969