Author Topic: smoke on acceleration after coasting  (Read 2230 times)

mastercraft10

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smoke on acceleration after coasting
« on: December 27, 2020, 15:29:06 »
280SL 1971    Fresh engine rebuild, top and bottom, and it runs beautiful.  correct idle, great acceleration and torque and very smooth.  However, after coming down a hill and then accelerating I get a serious blue smoke out the tail pipes.  I know the common cause is bad valve stem seals but mine are new as are the valve stems.  Normal driving on flat roads I see no smoke.  is there a way that the extreme vacuum could be pulling oil from the crankcase other than threw the valve stems?  I only have about 150 miles total since rebuild.  Temp is 180 F.  Do I just drive it and put miles on it to see if it gets better???

ja17

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Re: smoke on acceleration after coasting
« Reply #1 on: December 27, 2020, 17:48:15 »
It could be that your engine is not broken-in. What was done on the total rebuild? What oil are you using to break in the engine? My advice is to put more miles on it and monitor the engine oil level and transmission fluid level if it is an automatic.
Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1982 300TD Wagon turbo 4spd.
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback

wjsvb

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Re: smoke on acceleration after coasting
« Reply #2 on: December 28, 2020, 02:53:05 »
Unlikely, but possible, is that a valve stem might be scored or a stem seal is faulty.  Have you pulled the spark plugs?
jon

67 250SL early
12 Jeep GC (gone but not missed)
69 300SEL 6.3 Euro project (gone but not forgotten)
81 280SL Euro 4spd

wayne R

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Re: smoke on acceleration after coasting
« Reply #3 on: December 28, 2020, 06:30:47 »
I agree with Joe here,so i will give a few tips on breakin here now, hope its not to late for you  Wjsvb,
but break in is most critical, in the the very start  and first 100 to 300 miles.
Fill oil filter about at least half full,
Only use mineral 5/30 or 10/30 engine  break in oil that has a  additive ZDDP or Zinc,premium brand filter and oil.and camshaft additive.
Prime the oil pump to avoid dry start up.
On startup for for first and after runs, drive with short 1 to 2 mile drives of varying speeds up to about 2000revs than continue
the same  up to  about 3000 revs  varying speed  and revs total of about 5 to 8  miles then  return home and switch off.
Let cool down that day , than do the same next  few days until you have completed about 100 miles.
Never on start up drive away and cruise for  say 3000revs for 100 miles at same speed and revs.---
Im not a expert ,i leant this from a General motors and toyota dealership service manager back in 1976 to1989,
that rebuilt hundreds of engines all his life ,i was sales manager of the same dealership in New Zealand.

Mike Hughes

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Re: smoke on acceleration after coasting
« Reply #4 on: December 28, 2020, 21:41:22 »
Use only regular petroleum based oil when breaking in an engine.  Synthetic oils are too "slick" and prevent rings from breaking in properly, which will result in excess oil consumption.
- Mike Hughes  -ô¿ô-
  1966 230SL Auto P/S
  Havana Brown (408)
  Light Beige (181)
  Cream M-B Tex (121)

Benz Dr.

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Re: smoke on acceleration after coasting
« Reply #5 on: December 28, 2020, 23:20:13 »
Smoking after a rebuild isn't normal. Assuming you used new parts I'm going to ask a few questions.

Did you use new pistons or just new rings?

Did you use shims under your cam bearings?

How much thread do you have showing on your ball studs?
1966 230SL 5 speed, LSD, header pipes, 300SE distributor, ported, polished and balanced, AKA  ''The Red Rocket ''
Dan Caron's SL Barn

1970  3.5 Coupe
1961  190SL
1985   300CD  Turbo Coupe
1981  300SD
2013  GMC  Sierra
1965  230SL
1967 250SL
1970 280SL
1988 560SEC

mastercraft10

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Re: smoke on acceleration after coasting
« Reply #6 on: December 30, 2020, 16:08:00 »
Thats what I thought about the faulty seal.  I have pulled the plugs and they look good, no real carbon deposits but the ceramic near the tip is black.  all look the same.

mastercraft10

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Re: smoke on acceleration after coasting
« Reply #7 on: December 30, 2020, 16:15:53 »
Thanks Joe, that's what I hoping, is that it's just not broke in.  I used the oil that was recommended on this site plus the zink additive.  This was a good running engine so I thought I would "freshen" up with new rings, valve stems and seals, all new bearings etc.  The work was all done by a trusted engine builder here in Denver.  I'm not in a big hurry so I think I will put some miles on it  and see what happens.

mastercraft10

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Re: smoke on acceleration after coasting
« Reply #8 on: December 30, 2020, 16:21:14 »
Thanks Wayne, I printed out your instructions and will follow threw as instructed.  It's pretty close to what I've done but I have run the engine up to about 3000rpm a few times.

LJHAMILTON

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Re: smoke on acceleration after coasting
« Reply #9 on: September 15, 2021, 13:29:07 »
Having a similar problem after a complete rebuild. Have about 500 miles on it since than. My mechanic suggested it was a leaky valve seal on the exhaust side. Did your problem clear up after driving more miles. Thanks