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  #1  
Old 03-15-2003, 09:46 PM
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Join Date: Feb 2002
Location: Orlando, FL
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420 engine smokes

After reinstalling my valve covers with new gaskets, they leak and the oil is burning on the manifolds obviously making it smoke. It seems like it is coming from the back of the valve covers, towards the rear of the engine. I have looked, and I cannot visibly see it seeping out. It does not leak at idle, only at higher RPMs when more oil is thrown to the top end I imagine. The torque is 3 NM, but my torque wrench only goes down to 5 NM, so what I did is torqued it to 5 NM and then I backed off a little bit. So is this leaking normal the first time you start it up with new gaskets, do they need to "break in"? Or do I need to fix something here?

I am assuming that the valve cover gaskets are the problem, since it makes sense....I hope it's not something else bigger!
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'86 420SE Euro
904 Midnight Blue, Gray Velour
Dad bought it new, now I own it.

"A Mercedes-Benz is like a fine wine, it only gets better with age."
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  #2  
Old 03-15-2003, 10:10 PM
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Join Date: Jul 2002
Location: visalia ca
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very common for the gasket to come off in the back.
check it by taking off the v/cover. you'll see it pinched.
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  #3  
Old 03-16-2003, 12:53 AM
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Join Date: Oct 2002
Location: Colorado Springs
Posts: 481
v/c and seals

Make sure you use new copper crush washers every time. Push the valve cover up towards the fuel distributer when you tighten down and do not over torque, i prefer using feel use a 1/4 inch socket and tighten to pinky finger strength you will feel the crush washers give that is the perfect amount.
m
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2005 320 CDI
2006.5 VW Jetta TDI
1991 560SEL (179000 Sold)
1972 280SEL 4.5 ('The Lead Sled' 320000 miles when sold.)
1972 220D (225000 when sold)
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  #4  
Old 03-16-2003, 02:41 AM
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Thanks guys for the help! I'll do that.
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'86 420SE Euro
904 Midnight Blue, Gray Velour
Dad bought it new, now I own it.

"A Mercedes-Benz is like a fine wine, it only gets better with age."
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  #5  
Old 03-17-2003, 10:15 AM
moedip
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Had the same problem on my 560 sel - drove me nuts for many months and several valve cover gaskets later - no cure. Problem? Warped valve cover! Put your valve cover minus gasket on a perfectly flat surface. If it can be rocked back and forth a little bit, it is warped. Overtightening the four cover bolts will warp these aluminum covers. Cure? Two choices. Buy new covers or do what I did - take the cover to a machine shop that can mill valve covers. They had to take off 7 mils from mine to get it flat again. Re-installed -MAKE SURE YOU DO NOT OVER TORQUE COVER BOLTS. Problem is gone. Cost was $70 Cdn. for the milling. Be sure to use new compession copper gaskets on the bolts when re-installing. Never over torque bolts - trust me!! Hope this helps. The puffing smoke is embarressing isn't it?

Last edited by moedip; 03-17-2003 at 10:21 AM.
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  #6  
Old 03-17-2003, 01:26 PM
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Location: Orlando, FL
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Yes it is embarrassing! I guess I will try the simpler methods first since the covers are a PITA to take off, and if not, I guess I will just have to yank them off and try milling them. Good idea, thanks!

I don't recall them leaking at all before I took them off, you don't think that my whopping 2 NM overtorque (which I did back off right after) could have warped them do you??
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'86 420SE Euro
904 Midnight Blue, Gray Velour
Dad bought it new, now I own it.

"A Mercedes-Benz is like a fine wine, it only gets better with age."
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  #7  
Old 03-17-2003, 01:36 PM
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Join Date: Sep 2002
Location: So. Calif.
Posts: 323
The covers warp on the LOWER EDGE above the sparkplugs . . . It warps when the engine is HOT alowing the gasket to run out over the edge of the head due to HEAT from the EXHAUST MANIFOLDS . . . When the engine COOLS the warp RETURNS to it's ORIGINAL SHAPE, which does NOT leak . . .
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  #8  
Old 03-17-2003, 01:55 PM
moedip
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mpnye - Mine were warped longitutially from front right to left rear. The long sides were flat and if only one side of the cover was put on the edge of the flat surface it was flat. When I say warped I guess it would be more accurate to say Twisted slightly. As mptje says - no leakage along the flats - only in rear corners. The diagnoses was done by Mercedes Dealership. Found it hard to believe but apparently it is not that uncommon. Until I put the cover on a flat surface and saw the warpage (twistage) myself, I was skeptical. When it came back from the machine shop - all wobble was gone and the cover no longer weeps in the back corner. According to the machine shop - who specializes in racing cars - it is very common for cast aluminum valve covers on racing engines to warp also if over torqued.
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  #9  
Old 03-17-2003, 02:01 PM
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Location: So. Calif.
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If you look at a NEW cover, you'll see a RIB that is cast along the LOWER LENGTH above the exhaust manifolds . . .
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