1997 STS Ghostly Noise from Vacuum Leak? - Page 2
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Northstar Engines and System Technical Discussion Discussion, 1997 STS Ghostly Noise from Vacuum Leak? in Cadillac Engine Technical Discussion; Well, work your way back. We know that the PCV valve works and I believe you said that the line ...
  1. #16
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: 1997 STS Ghostly Noise from Vacuum Leak?

    Well, work your way back. We know that the PCV valve works and I believe you said that the line is clear. There has to be an obstruction somewhere between the cap and the PCV valve I would think unless there is something missing at the cap. My '03 engine is too difference to try to compare. My neighbor bought my '97. If no one can come up with anything, maybe I can get a peak at it some day.

  2. #17
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    krimson_cardnal is offline Cadillac Owners Enthusiast
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    Re: 1997 STS Ghostly Noise from Vacuum Leak?

    iconokrass - Are you experiencing any other "classic" vacuum leak symptoms? Ebrake release when putting car in gear? Dash vents working properly? I'll be looking at my 96NorthStar and try and see if this is what's been plaguing me. Not sure, but it should be a similar set up as my DeVille - any one? Sounds like the connection in picture 3 is the problem child. K_C

  3. #18
    iconokrass is offline Cadillac Owners Member
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    Re: 1997 STS Ghostly Noise from Vacuum Leak?

    Don't have access to the car at the moment. What is an "ebrake?" What should I be looking for in the vents--just that I get air from all of them when it is on?

  4. #19
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    krimson_cardnal is offline Cadillac Owners Enthusiast
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    Re: 1997 STS Ghostly Noise from Vacuum Leak?

    Emergency brake. It releases on a shift into gear via a vacuum actuated switch - at least on my 96DeVille. your's could be electronic, not sure. Same w/ vents. W/ A/C on and the dash vents open. This too is vacuum operated. I have a vacuum leak some place. Intermittent at that. Ebrake and dash vents some times work??? Driving me crazy. As soon as I'm done stripping paint I'm pulling the beauty cover on my NorthStar and have a look-see. K_C

  5. #20
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    krimson_cardnal is offline Cadillac Owners Enthusiast
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    Re: 1997 STS Ghostly Noise from Vacuum Leak?

    Pulled the beauty cover and see your connection. That hose comes off the intake and goes to the PVC. Connection at the intake end is secure. Your's seems to be faulty if it isn't holding the hose securely. I didn't pull mine, but it is on there tight. Guess would be there's a nipple under there the cap presses on to, might be busted. It is part of the manifold, so if the bit busted isn't on the hose end it's on the manifold end - possibly time for a new manifold. Take a close look inside that cap and see what you can see. K_C

  6. #21
    roger greeb is offline Cadillac Owners Member
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    Re: 1997 STS Ghostly Noise from Vacuum Leak?

    yep pcv and dont expect to buy the fittings at advance, o rielly's nor autozone...i made my own...from tubin on the shelf..mine split on my 97 sls. cant believe u didnt experience a huge missfire...

  7. #22
    krimson_cardnal's Avatar
    krimson_cardnal is offline Cadillac Owners Enthusiast
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    Re: 1997 STS Ghostly Noise from Vacuum Leak?

    Thanks Roger. I think the problem iconokrass is having is on the end were it connects to the manifold. His connection seems loose. What's under that cap the PVC hose connects to at that end? K_C

  8. #23
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    Re: 1997 STS Ghostly Noise from Vacuum Leak?

    Try clamping it with a nylon wire tie. Cheaper and easier than a new manifold.

  9. #24
    iconokrass is offline Cadillac Owners Member
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    Re: 1997 STS Ghostly Noise from Vacuum Leak?

    You know, I don't ever use the emergency brake, so I can't answer that question. On the vents, I'll have to check.

    I did an interesting test last night... I pulled the hose again and made absolutely sure it was clear (e.g. I could blow through it with ease.) I then pulled the pcv valve and made sure I could pull air through it. And, finally, I left the pcv valve out of the equation and put the cap on the firewall end directly into the socket the pcv valve came out of and fired the engine. And I had the same problem... The cap on the near end still collapsed and made hissing and other sounds as it did in the photo when the pcv valve was in place.

    I believe I understand that the point of the pcv valve and the tube running to the intake manifold is basically to vent and burn off exhaust gasses that blow past the rings into the crankcase during the combustion process by shunting them back into the combustion chamber. That means, to me, that there must be a clear line of access for the gasses that starts in the crankcase itself and runs up through the assembly at the firewall that apparently houses the cam(s) and then through the pcv valve, along the tube and into the intake manifold, making a circle of flow. I can see that by creating a port at the intake manifold (where the tube coming from the pcv valve It occurs to me, however, that if the pressure builds in the crankcase from exhaust gasses being pushed into it and that pressure (and the gasses) must be relieved

    From what I have learned on this forum, this suggests to me that the blockage must actually be past the pcv valve and actually inside the engine itself.

    ??

  10. #25
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    Submariner409 is offline If it won't run, chrome it
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    Re: 1997 STS Ghostly Noise from Vacuum Leak?

    If I remember correctly, you should be able to look into the 3/4" PCV "socket" in the cam cover. Shine a pencil beam flashlight in there and see if the oil splash baffle in the cam cover has collapsed and is blocking off the PCV and its vacuum source. You might be able to push the baffle back open with a Philips screwdriver.

    Back 8 months or so in this forum there's a thread titled "A River Runs Through It..." or something close. It's a treatise on just that oil baffle and what can happen to it. Check it out.

  11. #26
    iconokrass is offline Cadillac Owners Member
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    Re: 1997 STS Ghostly Noise from Vacuum Leak?

    I fixed it...

    I grabbed the little bastard by his neck and wrapped a hose clamp around him. That shut him up good!

    However, I noticed a split in the connector, so I assume I'll be hearing from him again soon...

    Thanks for all your help. I was particularly interested in the idea of looking through the socket for the pcv valve to see if there is some kind of blockage there and when I do I'll report back.

    You know, I had a mechanic look at it before and he couldn't figure out what the noise was, so I'm sure you guys saved me serious money (not that it should have cost me that much, but it would have...)

    Thanks so much!

  12. #27
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    krimson_cardnal is offline Cadillac Owners Enthusiast
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    Re: 1997 STS Ghostly Noise from Vacuum Leak?

    Hey, a fix is a fix. You saved a bundle for sure. So the cap part was at fault. Bet that hose clamp holds perfectly well. K_C

  13. #28
    Ranger's Avatar
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    Re: 1997 STS Ghostly Noise from Vacuum Leak?

    I grabbed the little bastard by his neck and wrapped a hose clamp around him.
    Glad you got "him" taken care of.

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