Trying to find what causes noticeable loud engine knock at idle on a 2009 S40 2.4i
First I wanted to check if it is a rod knock and tried to remove sparks, manually crank and check for damaged crankshaft bearings, noticed that the sparks plug area of first cylinder is covered with oil, so was the spark plug itself as photos below show:



The oil on spark plug and it's surrounding area is clean, checked the engine oil, it is low and black dirty.
I appreciate any hint as what could cause so much oil in one cylinder and how it may relate to engine knock.

 

:There shouldn't be oil in the spark plug cavity, so my guess is that the plug was simply loose, and the "knock" you were hearing was just exhaust gasses bypassing the plug. I don't know how long those plugs have been in there, but it might be a good time to swap 'em out for some new ones (after verifying that putting the #1 plug back in properly stops your "knock".

At least, that's the best possible scenario. ;-) There certainly could be a real knock in your low end, in which case it would be totally unrelated to oil around your spark plug (and for which a new set of plugs would be a total waste of money).

 

I happen to have a set of plugs, so I am going to change it and the dirty oil and hope for the best scenario .
If knock prove to be at low end as you mentioned and I needed to change crankshaft bearings, why changing sparks will be a waste of money?

 

Sorry for any confusion - lots of folks would just opt for a boneyard engine, or even scrapping the car if they have a fatal flaw in the engine. If you are planning a rebuild (if the bottom end is toast, that is) then yes, new plugs are just part of the investment in getting that engine back to as-new condition.

Thing is, I'll bet dollars to donuts that the engine will be nice and quiet with that plug put back in correctly (or a new one, either way).

 

You lost the bet, I changed all 5 sparks and mounted the top back on, it still knocks loud.
Drained dirty oil and cranked using that 30mm socket , with spark plugs out pushed down
on 3 of 5 cylinders one at a time when each slightly passed their highest position, there was no
movement nor a click, so can not say the knocking noise is due to rod knock( worn crankshaft
bearings).
Because the engine starts and runs, it could be the head, then I have to spend $600 getting another
but I do not know how to check for bad head and valves, I appreciate advice here.

 

Get a mechanics stethoscope and find the source of the knock. Harbor freight sells a very low cost version. Or get a rubber hose and hold one end to your ear while using the other end to search for the source.

 

I would after I am done with oil pan that now I started to remove. Drained the dirty oil, have another S40 that runs perfect at 140000 miles and this one is knocking loud at 123000 miles, so I rather see how dirty oil pan is and check bearings by hand( did not notice movement from the top with sparks out),
The clean oil on corner spark plug should have been just oil spill when someone was adding oil because the oil cap is next to this corner spark plug.
Had another car that was knocking loud like this, turned it off and checked, there was little oil, added oil car ran good afterward. This one had plenty of dirty oil
but knocking loud as bad as the car with no oil , so I turned off right away rather than try to find the source by listening. I was told more damage could occur running
the engine that knocks loud and getting no oil.

 

Well if it's a spun rod bearing then no amount of clean oil will help. Let us know what you find?

 

Removed the oil pan and checked bearings, they are worn and I need a new set of bearings. My Vida readout say B5244S7 engine but there is a color code chart and many bearings to choose, I can not figure out which ones are for my engine crankshaft.Also need to find the torque values.