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Cadillac STS Forum - 2005 through 2012 Discussion, Intake Manifold Bolts in Past Cadillac Vehicle Discussion; Finally checked mine, and yep, all ten were loose. At least three weren't even finger-tight. Tip: You have to have ...
  1. #31
    mckellyb is offline Cadillac Owners Enthusiast
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    Re: Intake Manifold Bolts

    Finally checked mine, and yep, all ten were loose. At least three weren't even finger-tight.

    Tip: You have to have either a 10mm crow foot or 1/4" socket/u-joint/extension for this to get under the fuel rail. A 3/8" drive isn't getting under there.

    I could not find my 1/4" u-joint, so I'm getting another. The crow foot wrench worked, but a 1/4" drive would have been SO much easier and quicker.

    I can't believe they cover up such a pretty engine with plastic. I'm sorely tempted to leave it off.

  2. #32
    chazglenn3's Avatar
    chazglenn3 is offline Cadillac Owners Connoisseur
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    Re: Intake Manifold Bolts

    Thanks for the tip, Kelly. I don't think I'm in the mood to remove the fuel rail. I need to get a 1/4" torque wrench and a new swivel. Off to Harbor Freight after work!

  3. #33
    mckellyb is offline Cadillac Owners Enthusiast
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    Re: Intake Manifold Bolts

    Besides all the obvious reasons to keep these snug, let me add one.

    I'm 99.5% certain tightening these eliminated a slightly rough idle, which was only sometimes. After a couple of days, I might be 100% certain on this. It seems worse in the afternoon, for some reason.

  4. #34
    EChas3's Avatar
    EChas3 is offline Cadillac Owners Master
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    Re: Intake Manifold Bolts

    Burnt pistons anyone?

  5. #35
    Dj Brady is offline Cadillac Owners Member
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    Re: Intake Manifold Bolts

    Quote Originally Posted by EChas3 View Post
    Burnt pistons anyone?
    :nod: Running lean = no bueno

  6. #36
    chazglenn3's Avatar
    chazglenn3 is offline Cadillac Owners Connoisseur
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    Re: Intake Manifold Bolts

    Found 8 out of 10 loose...much smoother idle.

  7. #37
    caddyfat2 is offline Cadillac Owners Fanatic
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    Re: Intake Manifold Bolts

    I checked mines today and what do you know? I found 6 that were loose. They were'nt that bad but loose nonetheless. I tightened them down in less than 5 minutes. I didn't torgue them down just tightened as tight as I could so I guess I'll have to check them again in about 2 months. Now I can put another 72k miles on my beast. Hurray.

  8. #38
    EChas3's Avatar
    EChas3 is offline Cadillac Owners Master
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    Re: Intake Manifold Bolts

    You may have over-done it. The recommended torque isn't much.

    Anyone else... take care. The spec is barely more than finger-tight.

  9. #39
    caddyfat2 is offline Cadillac Owners Fanatic
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    Re: Intake Manifold Bolts

    Quote Originally Posted by EChas3 View Post
    You may have over-done it. The recommended torque isn't much.

    Anyone else... take care. The spec is barely more than finger-tight.

    Yes Echas3 you are correct but my train of thought on that was make them a little tighter seeing the factory spec didn't work because everybody who checks them finds them loose. I will keep an eye on them.

  10. #40
    caddyfat2 is offline Cadillac Owners Fanatic
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    Re: Intake Manifold Bolts

    Quote Originally Posted by EChas3 View Post
    You may have over-done it. The recommended torque isn't much.

    Anyone else... take care. The spec is barely more than finger-tight.

    Yes Echas3 you are correct but my train of thought on that was make them a" little tighter "seeing the factory spec didn't work because everybody who checks them finds them loose. I will keep an eye on them.

  11. #41
    caddyfat2 is offline Cadillac Owners Fanatic
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    Re: Intake Manifold Bolts

    UPDATE: It is now two days since I tightened up the intake bolts and now my car runs as smooth as silk. Before you were able to tell it was running but now you can't even tell it's running it's so smooth. It hasn't idled so smooth since I purchased it 4 years ago. Wow what a difference.

  12. #42
    mckellyb is offline Cadillac Owners Enthusiast
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    Re: Intake Manifold Bolts

    Another update.

    I re-checked mine yesterday, after finally getting a 1/4" drive U-joint, and they were all tight. Granted, I'd tightened them just a week ago, but still.

    Let me caution everyone, there is one on the driver's side, middle of the engine front-to-back, under a part of the fuel rail which prevents using a socket on it. I had a crow-foot wrench, but was still damned unpleasant. Take your time on it is all I can say.

    Probably should've tried a box-end wrench, but the crow-foot was doing something. Not much, but a little.

    Oh, and I'm pretty certain my MPG is up about 1 MPG. This car gets driven the exact same way, every day, and I'm in the low-22's on the VIC (vehicle information center). Idle is definitely smoother.

  13. #43
    1crock is offline Cadillac Owners Member
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    Re: Intake Manifold Bolts

    Y'all might be interested to know this problem is not unique to the STS. My '96 Suburban had the same problem and so have a handful of other vehicles with a plastic lower intake. The answer is to use LocTite on them and the problem won't come back. I did that when I changed the intake gaskets on the Suburban. You can do it on STS (or anything else) by removing the bolts one at a time. The message here is, check them on anything you drive.

    Caddyfat2, as an engineer I cringed when I read your "...as tight as I could..." Torque values are not used to make sure the bolt won't come loose, there are several engineering considerations involved including proper gasket seal and even strength of the parts. I really encourage you to correct what you've done with the proper torque. IF you don't want them to come loose again, LocTite is your answer.

  14. #44
    desilpj is offline Cadillac Owners Member
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    Re: Intake Manifold Bolts

    Found 2 bolts loose. Idle is smoother now. If not already mentioned, using a 1/4" drive with a universal and extension, lets you tightened all the bolts.

  15. #45
    MacMuse's Avatar
    MacMuse is offline Moderator
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    Re: Intake Manifold Bolts

    I swear I might stick this thread to the first page.

    I took mine in for a thermostat problem yesterday (still under CPO) and asked about the manifold bolts. They scoffed, of course, but ran a leak test and found ... wait for it ...





    a leak.






    they replaced 8 runner seals and a brake booster vacuum host. Ye gods what a difference. Light pedal acceleration from 0-40MPH appears to be much smoother. And I've had a noticeable hesitation when lightly accelerating from a cruising speed of 33-39mph that seems to be gone now as well.

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