Smoking after valve stem seal replacement.
02-05-2015, 03:24 AM
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W203 C320
Smoking after valve stem seal replacement.
My C320 was belching out bluish smoke on startup after sitting off for a while, or after idling for a long time (like on a congested motorway). Other than that, no smoke during normal driving. It was also consuming a fair bit of oil. Definitely not head gasket.
Took it to an indy and he said it was valve stem seals, he ruled out piston rings and the PCV system since the smoking didn't happen all the time and even taking it to 4000rpm up a hill didn't necessarily produce it. He also replaced valve cover gaskets and spark plugs at the same time.
I took the car back and went for a 40 minute city drive, to my horror I saw smoke billowing behind me when I took off after spending ages idling in a congested motorway, cleared up after a few seconds. I went home and left it sitting in the garage for a few hours and started it again, I could see copious amounts of smoke coming from the exhaust, just like the original problem. My country's got a 3 day public holiday and I won't be able to contact any mechanic till monday. I'm at a loss to understand, if it isn't rings or seals, how else can oil get burnt? I did a bit of googling and it could be valve guides but shouldn't they have found that if they were replacing the stem seals?
Took it to an indy and he said it was valve stem seals, he ruled out piston rings and the PCV system since the smoking didn't happen all the time and even taking it to 4000rpm up a hill didn't necessarily produce it. He also replaced valve cover gaskets and spark plugs at the same time.
I took the car back and went for a 40 minute city drive, to my horror I saw smoke billowing behind me when I took off after spending ages idling in a congested motorway, cleared up after a few seconds. I went home and left it sitting in the garage for a few hours and started it again, I could see copious amounts of smoke coming from the exhaust, just like the original problem. My country's got a 3 day public holiday and I won't be able to contact any mechanic till monday. I'm at a loss to understand, if it isn't rings or seals, how else can oil get burnt? I did a bit of googling and it could be valve guides but shouldn't they have found that if they were replacing the stem seals?
Last edited by Engapol; 02-05-2015 at 03:27 AM.
02-05-2015, 09:34 AM
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I should also mention that the engine is suffering from some sludging, could this cause oil to leak past the seals regardless of whether they are new or not?
The mechanic told me to get it in for a flush and oil/filter change at my next service in 3500km.
The mechanic told me to get it in for a flush and oil/filter change at my next service in 3500km.
02-05-2015, 10:42 AM
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07 E63 + 07 CLK63CAB
Valve seal will correct a smoking problem provided the valve guides are not worn excessively. Look for a plugged or disconnected PCV valve, another point is if the timing is out (stretched chain or jumped tooth)the piston will draw oil past the valve guides when drawing in the next air/fuel charge, sort of a vacuum effect. Another possibility is the car needs to be driven on a long trip to remove the oil/carbon deposits behind the valve head from the previous running with the old seals.
