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Blue smoke at cold start

Tiny
SEVAG P
  • MECHANIC
  • 1994 PORSCHE 911
  • 3.6L
  • 6 CYL
  • 2WD
  • MANUAL
  • 45,000 MILES
Hi,

I rebuild an air cooled Porsche engine, new factory (mahle) cylinders and pistons installed, complete seals and gaskets replaced, now during cold start blue smoke appear for a while then disappear, engine run in after rebuild about 70 miles, is it the new rings still doesn't seated properly? Manual doesn't mention after engine rebuild how many miles should be engine break in.

Thank you.
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Sunday, January 26th, 2020 AT 11:53 AM

2 Replies

Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
They should not smoke at all after they are rebuilt. Clearly some may burn out some residual oil from the assembly process but that is just until after they warm up.

If it goes away after it is warm, I suspect the valve guides and seals are leaking. Normally when this is the issue the leak is very small and once the seals warm up they stop and the smoke goes away. Also, if you shut it off and restart it, it will not smoke because the seals are warm.

If it were me, I would replace the valve stem seals and retest it. If this doesn't do it then it is the rings.

https://www.2carpros.com/articles/blue-smoke-from-engines-exhaust
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Sunday, January 26th, 2020 AT 3:18 PM
Tiny
SEVAG P
  • MECHANIC
  • 405 POSTS
Hi,

Then engine doesn't need further break in, because we just drive about 70 miles?
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Sunday, January 26th, 2020 AT 8:51 PM

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