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Old 12-19-2012, 09:57 PM   #1
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Default more vacuum pressure after lim gasket change?

First want to say thanks to everyone who is on this site...the info has been great and helped me through so many fixes with my car including the lim gasket change I recently did...so I have a 2005 sle at 142000 miles I have just done the lim gaskets and a new uim and egr luckily it was only an external coolant leak from both gaskets...it seems after the change that there is a lot more vacuum throughout the motor I am getting a slight hissing sound from the air box and when turning the car off it does the same until it is depressurized?..also when I take the oil cap off with the car running it kind of stumbles and seems like a huge vacuum leak same even with the dipstick...common sense would tell me this is a good thing but prior to the change it never did this...the car runs great no check engine and I sprayed throttle body cleaner after breplacement just to check...seems fine no change at idle....so has anyone e
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Old 12-19-2012, 10:02 PM   #2
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Originally Posted by ak1920 View Post
First want to say thanks to everyone who is on this site...the info has been great and helped me through so many fixes with my car including the lim gasket change I recently did...so I have a 2005 sle at 142000 miles I have just done the lim gaskets and a new uim and egr luckily it was only an external coolant leak from both gaskets...it seems after the change that there is a lot more vacuum throughout the motor I am getting a slight hissing sound from the air box and when turning the car off it does the same until it is depressurized?..also when I take the oil cap off with the car running it kind of stumbles and seems like a huge vacuum leak same even with the dipstick...common sense would tell me this is a good thing but prior to the change it never did this...the car runs great no check engine and I sprayed throttle body cleaner after breplacement just to check...seems fine no change at idle....so has anyone e
experienced this after a lim gasket change is it due to the engine sealing better or did I screw something up
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Old 12-19-2012, 10:21 PM   #3
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I would have to say somethings not right. I have done lots of intake reseals and have never had one that would stumble when the oil cap is removed. The hissing sound would be a vacuum leak. You should put your year, make, model, and engine size in your signature. That way the people that are possible going to help you know what you have. This would make it easier. Thank you.
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Old 12-19-2012, 11:20 PM   #4
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The biggest cause of a whistle/screech that changes when you removed the oil cap is usually caused by a bad/missing o-ring on the pcv valve.
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Old 12-19-2012, 11:32 PM   #5
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The biggest cause of a whistle/screech that changes when you removed the oil cap is usually caused by a bad/missing o-ring on the pcv valve.

More vacuum is a good thing, but only in the intake manifold, not in the crankcase. Rjolly is probably on the right track with telling you to check the PCV valve. Positive Crankcase Ventilation = no vacuum in crankcase.
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Old 12-20-2012, 09:46 AM   #6
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Sounds like it'* BAD, stuck open. $0.02
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Old 02-10-2013, 07:43 PM   #7
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The missing O-ring on the PCV valve will also cause a a very loud squeal, sounds like a belt. If you were to take the dipstick, or oil cap off it goes away due to vacuum pressure in the crankcase. Good luck mang!
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