Expert: Roland Finston - 10/8/2011

Question
Hi, I have a 1999 Sebring Convertible JXI.
Just recently the engine started smoking.
It's smoking from front, right under the plastic cover where you put the oil in. The black cover says 2.5L V-6  24 Valve.
Image of smoke source attached.

Thank you for any help you may give me.

Regards,
Cody

Answer
Hi Cody,
The most likely reason for smoke or vapor to be exiting under the edge of the valve cover is that there is excessive blow-by pressure in the crankcase of the engine which would normally be sucked into the intake manifold via the positive crankcase ventilation valve (pcv valve) which is on the side of the same valve cover in your photo but at the front edge of the cover (front of the engine). It goes through a rubber grommet into the inside of the valve cover and it has a vacuum hose attached to the other end after a 90 degree bend which goes to the intake manifold. That valve could be gummed up closed or have failed spring inside of it, or it is also possible that the hose from the valve to the manifold has fatigued and is leaking. In any case, gently remove the valve from the valve cover, start the engine and notice whether you hear air being sucked into the valve and if you put your thumb over the opening it should feel strong suction. If not, then I would remove the hose from the other end of the valve and do the same test with the end of the hose proper. If you don't have vacuum on the hose then the hose is 'open' somewhere on the way to the manifold and should be replaced. If the hose 'sucks', then if you didn't get good suction at the valve opening then I would replace the PCV valve. It is very inexpensive so you might want to replace it anywat. Be sure to gee the correct valve for that engine. If the valve circuit fails then you will definitely get blow-by vapor/smoke coming out as you described because of the pressure inside the engine that is not being relieved. Let me know if servicing the valve circuit doesn't solve your problem. It could simply be due to the gasket on the valve cover being 'open' or the valve cover bolts a bit loose which then allows oil to leak out and that can smoke when it touches hot surfaces below the point of leakage. The fix would be the tighten the valve cover fasteners and if that didn't stop then remove the valve cover and replace the gasket. The torque spec for the cover screws is 31 inch-pound which is very little so don' strip or break them trying to hard to tigheten them down.
Roland