Exhaust Sucking Air + Others???

Posted by boostedzxtt, Jan 7, 2007
Newbie Forum - Beginner/newbie/general DSM modification questions. First mods, how to run 10's when you haven't run 12's yet, any tech question that doesn't fit in another tech forum.

  1. boostedzxtt

    boostedzxtt Probationary Member

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    Recently I replaced a Valve Cover Gasket on a 91 TSI AWD, because it was leaking oil. Then I found out the valve cover was cracked and that was causing the leak. This is the least of my worries right now though. After installing the gasket I drove the car around the block and it ran without problems, so I thought I'd just look for a valve cover.... untill I started it up today. The car is idling horibbly and it seemed to be coming from the valve train, but it is so loud that I can't even narrow it down to a certain area. Plus if you hold your hand over the muffler you can litteratly feel it sucking in, instead of blowing the exhaust out. Keep in mind that the car was running fine the day before. Anyone have any idea what this could be? Also I will check the codes later today or tomorrow.
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  2. exile

    exile Proven Member

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    I am basing my answer on an old-guy V8 trick.

    Typically when your exhaust is sucking in air it means that you have a blown head gasket.

    The "trick" is to hold a dollar bill up to the muffler and if it sucks and blows it's most likely a blown head gasket. Try a compression test to confirm this.
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  3. CTP_MADDOG

    CTP_MADDOG Probationary Member

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    i agree with exile
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  4. Stainbox12

    Stainbox12 Proven Member

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    Those v8 owners must have a lot of money then. Wouldn't it be the same with a piece of paper? :p
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  5. Locke

    Locke N/T DSM Wiseman

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    A chipped or bent exhaust valve can cause this, damaged seat, damaged spring, exhaust cam out of alignment (jump time, broken dowel), etc...

    I would do a compression and poor mans leak down test, and check the cam alignment. Having to remove the head would be likely, to repair the issue.
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  6. sawnuoff

    sawnuoff Proven Member

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    if there is noise coming from the valve cover i would check the timing,sounds like all the valve lifter are ticking like crazy, belt maybe off a tooth or more.
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  7. Locke

    Locke N/T DSM Wiseman

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    Cam time being off by one tooth wont cause clash. It would have to be several teeth off to cause valve noise.
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  8. boostedzxtt

    boostedzxtt Probationary Member

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    Alright thanks for the help so far. I've just done a compression check and it reads as follows 152, 149, 130, 125, on a cold engine seems like its probably the head gasket. Plus I found a large vacuum leak after the maf on the intake so the leaness might of not helped in the situation.
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  9. exile

    exile Proven Member

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    boostedzxtt, if you have a chance, I'd remove the head before ordering another head gasket, just in case that isn't the issue. I'm not really sure why a blown head gasket would make a loud noise, I could understand how skipped timing could however.

    You shouldn't drive the car until you have this issue fixed, if you skipped by a tooth or two it's still possible to drive (it would drive like sh** as you described) but it makes it easier to skip more teeth which could ruin the entire engine.

    Check vfaq.com and do some research on checking your timing. You're on the right track however, low compression.. noise.. air sucking inward from the exhaust all point towards those two things.
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  10. Locke

    Locke N/T DSM Wiseman

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    To be sure, add some compressed air to the cylinders, one at a time, and listen and look. (poor mans leak down) should help determine exactly whats going on. Also check the cam alignment. These are free/easy thing to do before spending to much more time/money. Just in case.
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  11. PSI NRG

    PSI NRG Proven Member

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    Is the car blowing any white smoke out of the exhaust? Usually if you pop a head gasket coolent will leak into one of the cylinders and burn causing white smoke. I thought the dollar trick or whatever was to determine if the valve seals were leaking not the head gasket?
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  12. boostedzxtt

    boostedzxtt Probationary Member

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    no, actually It does not smoke at all. That is what through me off also. But I'm already pulling the head. I ran out of light tonight, but tomorrow I'll finish pulling it, and I'll check the valve seats and head gasket.
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  13. Locke

    Locke N/T DSM Wiseman

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    the dollar trick is for checking valve seating issues
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  14. boostedzxtt

    boostedzxtt Probationary Member

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    well I got the head off last night (So much Ice and Snow I couldn't work on it the last few weeks) The head gasket is fine. I see no "visable" cracks. I am not 100% certain, but it almost appears that one of the valves hit the piston, but keep in mind it's hard to tell, because that valve looks like it seats fine. What do you guys think it is? BTW compression before the teardown was roughly 150-150-130-125.
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  15. boostedzxtt

    boostedzxtt Probationary Member

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    okay, just got a suggestion from a mechanic. He said that it was possible that there was valve float and due to worn springs and the valves may have hit the piston (and if that did not bend them, they wouldn't close fast enough to get a high compression reading) It makes sense if you think about it.
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