replaced valve cover and noticed the discoloration on cylinders 4,5 and part of 3.

Thoughts?!

car is 2012 TL 3.5 with 165,000 miles

 

This is a design feature of all J engines, yours is very clean under the cover.

 

interesting! I had read something about air flow or the heat flow of the engine as being why some cylinders get burnt.

I also read that tight valves can cause burning? I adjust some of valves in the front, they were tight.

car now ticks more than before the adjustment.

 

Second Altair47, Your valve train looks pretty clean. The J35 crankcase ventilation system runs all the piston blowby gasses into this valve cover and back into the upper intake plenum through the hose on the passenger side of the front bank valve cover. You had to take off that hose to remove the valve cover. Your seeing a some staining of the rocker arm assembly as the gasses make there way into that hose and back into the intake.

 

That’s a relief to hear! Thanks

Yeah the PcV is on the right of the front valve cover and there is a slotted shield that runs along the top/ underside of the front valve cover. Exactly like you say, that is circulating gases causing stains.

I was worried something was burning or tight valves causing an issue.

thank you both!