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Old 11-24-2013, 01:39 PM
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Join Date: Jun 2008
Posts: 463
Can these things really cause significant vacuum leaks?

I happened to find the article below while searching for the elusive source of a possible vacuum leak in my 81 380sl. According to the article, vacuum leaks can be caused by a valve cover gasket, oil cap gasket, and even the rubber grommet on the dipstick.

Has anyone ever heard of or experienced these things affecting the idle on a 116 or 117?

Pelican Technical Article: Mercedes Benz - Fixing Common Vacuum Leaks

Thanks in advance for your usually enlightening replies
1981 380SL
Chassis: R107.045
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Old 11-24-2013, 05:04 PM
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Join Date: Jan 2012
Posts: 5,980
It isn't so much an intake manifold vacuum leak as it is unmeasured air. In a air flow type fuel injection system, unmeasured air will let the engine run lean.
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Old 11-25-2013, 11:16 AM
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Join Date: Jun 2008
Posts: 463
Thanks for the response. But i can't imagine how "unmeasured" air entering the crankcase from the dipstick or filler cap could affect the fuel injection system, since (1) there's plenty of air in the oil pan already, (2) the oil isn't pumped under vacuum into the crankcase or onto the cam shafts and rockers, and (3) gravity returns it to the oil pan.

In fact, I assume that's why the air isn't measured in the first place; i.e., it doesn't figure into the combustion mixture, unless there's something far more wrong with the system -- e.g. a cracked head.
1981 380SL
Chassis: R107.045
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Old 11-27-2013, 09:47 PM
82 380SL & 96 SL500
Join Date: Jun 2008
Location: Southern Illinois
Posts: 245
I don't buy it....

If that were the case, removing the oil filler or dipstick while idling would immediately screw up the cars idle.
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Old 12-03-2013, 12:43 AM
Join Date: Dec 2005
Location: Northern,Ca
Posts: 707

I am wondering how the oil system is connected to the fuel system, other than PCV. The logic has me stumped. Oil leaks don't affect how an engine runs until pressure gets low.

84 280sl
82 300d euro
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