Working on a friends car. 2010 Justa. The knock started the other day. I first thought it was the timing chain, but after removing the valve cover and inspecting, it doesn’t appear to be the problem. Inspected the spark plugs and no unusual misfire. No CEL’s either.

I made a short video with the sound.
https://drive.google.com/open?id=1VL...YX54_1NDwNRHf8

Any ideas?

 

Did it run low on oil at some point? Knocking is never good... Timing chain would be a rattle. Misfire would make the engine run rough.

 

Let’s assume, yes, it got low on oil. It was a quart low when they brought it over for me to inspect.

 

Corrected the permissions. You should be able to see the video now

 

check the serpentine belt.

 

That has all the sounds of a bad rod bearing. If it suffered oil starvation for any length of time, that would be an obvious condition.

 

If you noticed, the sound does NOT get louder as he revs the engine. It stays the same pitch but becomes faster. for that reason I bet it is not a bad rod bearing but a $10 belt...I had a NAM member bring me his car for the same "shop diagnosis" only to find a chipped belt...poor guy was asked to replace his engine by two shops!!

 

That is correct, the sounds does NOT get louder with RPM’s. For the cost, the belt is an easy and cheap part to replace and see what happens. My neighbors 17 yr old daughter drives the car and they aren’t auto people, so they always take their cars to the dealer or shop. If I had to guess, they never check the oil, so I can’t say for sure if it was ever low and overheated.

I’ll post the results after I replace it.

 

While you at it, check the pullies. Sometime they chip away from thr inner side (crankshaft and water pump pulley).

 

Found the solution. MiniToBe called it, Serpentine Belt. Some of the ribs had broke off and when it passed through the friction wheel, it “bumped” causing the sound.
Replaced the belt, silent as a mouse.

 

Wow...now that's a belt that needed to be replaced!