Engine sucking air from oil cap...why?
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Engine sucking air from oil cap...why? I noticed that there is a considerably strong vacuum/suction when I remove the oil filler cap while the engine is on. The engine while then very slightly start to idle rough just like when you disconnect a vacuum hose. The same thing when I remove the dip stick.
Is this normal?
Maybe this is not related but its worth mentioning just in case...I'm getting the oil light anytime the engine is warm and idleing. Gotta keep the the rpm at or above 1k for the light to disappear. Also a hit a huge rock a while back punctured my oil pan. Thank God I didn't loose any oil while engine was running as I pulled over soon as I hit the rock. JB welded it and its beautifully held up, so not getting any leaks from there.
So yeah, about the suction...any ideas?
Is this normal?
Maybe this is not related but its worth mentioning just in case...I'm getting the oil light anytime the engine is warm and idleing. Gotta keep the the rpm at or above 1k for the light to disappear. Also a hit a huge rock a while back punctured my oil pan. Thank God I didn't loose any oil while engine was running as I pulled over soon as I hit the rock. JB welded it and its beautifully held up, so not getting any leaks from there.
So yeah, about the suction...any ideas?
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If it's a LS1 GTO the air for the crankcase ventilation comes from a hose connecting the passenger valve cover to the TB. Have you replaced the TB or installed some sort of "catch can"?
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Its a fly by TB thou, stock. Aussie so a little different. Here is a pic...
Last edited by Freefallin; Aug 14, 2014 at 10:17 AM.
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The vacuum comes from the intake manifold and it's supposed to do that so it clears blow-by out of the block. Try putting everything back on and just disconnect that hose where you have the arrow. You should feel vacuum on the end of the hose and if the part it goes into is clear you should be good to go and how it should work.
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The vacuum comes from the intake manifold and it's supposed to do that so it clears blow-by out of the block. Try putting everything back on and just disconnect that hose where you have the arrow. You should feel vacuum on the end of the hose and if the part it goes into is clear you should be good to go and how it should work.
Engine do require it. I can't speak to why you didn't notice it on others but all engines have piston blow-by. Besides being bad for the oil and thus the engine, that blow-by pollutes. Old cars used to have a "draft tube" that just discharged it to the atmosphere. Modern cars take air from after the MAF (and thus is accounted for by the computer), pull it through the crankcase taking the blow-by with it and then dumping it into the intake manifold behind the TB blade where there's vacuum when the blade is closed/partially closed and the hydrocarbons get burned in the engine.
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Good vid, the source of your high vacuum is your connection to TB I wonder how much oil is socking in to the motor.
You can reduce the volume of vacuum by reducing the inside diameter of the hose, these can be accomplished by pushing another piece of hose into existing one, please note vacuum is not a bad thing, it is when too much oil is absorbed by it and introduced into the combustion chamber.
You can else connect your vacuum source from the intake manifold rather than the TB or the intake track as is on the LS2, in which these condition was corrected when using the Fast intake manifold.
Good vid, the source of your high vacuum is your connection to TB I wonder how much oil is socking in to the motor.
You can reduce the volume of vacuum by reducing the inside diameter of the hose, these can be accomplished by pushing another piece of hose into existing one, please note vacuum is not a bad thing, it is when too much oil is absorbed by it and introduced into the combustion chamber.
You can else connect your vacuum source from the intake manifold rather than the TB or the intake track as is on the LS2, in which these condition was corrected when using the Fast intake manifold.
The best way to remove oil from the intake is not to restrict it but to use a coalescing filter in the path between the valley cover and manifold. There are many "catch cans" commercially available but IMHO all of the ones I've seen are too small and don't contain material to condense oil vapor efficiently. They also cost a lot for what they are. Most seem to get picked by how "pretty" they are. I made a large one for my GTO out of PVC filled with stainless Chore Boys and tucked it out of sight in front of the driver's side wheel so the bay isn't cluttered up with more crap. It's so efficient that it condenses water vapor out too.
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You have a problem, that's not normal. Check the inlet hose at the frt of the valve cover above the oil cap. Pull it off and see if it stops this. If it does the hose is blocked or the ylave cover inlet where hose goes on is blocked. That engine is badly sludged up, most likely the inlet where the hose goes in is blocked.
