heavy vacuum at oil cap
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Newbie
Joined: Aug 2019
Posts: 2
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2014 glk350
heavy vacuum at oil cap
it sounded like a belt squealing so i replaced the belt ,tensioner, water pump, alternator, and both idler pulleys but squeal would return when engine reached operating temp. so i tried running engine without the belt and that is when i discovered that the engine is sucking air through the oil cap and dipstick tube. when you try to take the oil cap off it is hard to pull up as the sucking is strong but when the cap is off the noise stops what causes this and how to fix it? 2014 glk350
Last edited by wwh396; Aug 31, 2019 at 05:32 PM. Reason: added year and model
Senior Member
Joined: Jul 2014
Posts: 422
Likes: 61
From: South East US.
2015 GLK350
Some vacuum in the crankcase is normal and needed for vapor extraction. Most cars have a positive crankcase ventilation valve (PCV) that connects between the top of the valve cover to the intake and manages the vacuum level. I'm not sure what it is called by mercedes. Maybe crankcase ventilation valve, maybe centrifuge cover? You may have a problem with this valve. Or maybe not. It's hard to trouble shoot these things over the internet with terse problem descriptions. Do you have a check engine light or any problem codes?
