2000+ Northstar Plenum Replacement steps - Page 3

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Cadillac Tech Tips - How to fix it Discussion, 2000+ Northstar Plenum Replacement steps in Item Specific Cadillac Discussion; 2004 Seville SLS Update: R&R Intake Plenum Gasket, TB gasket, and Intake Manifold Gaskets. Also, cleaned TB. Notes: No tear ...
  1. #31
    Closet Boy's Avatar
    Closet Boy is offline Cadillac Owners Fanatic
    Automobile(s): 2004 SLS
    Join Date
    Jun 2005
    University Heights, Ohio

    Re: 2000+ Northstar Plenum Replacement steps

    2004 Seville SLS

    Update: R&R Intake Plenum Gasket, TB gasket, and Intake Manifold Gaskets. Also, cleaned TB.

    Notes: No tear in plenum gasket; however, was oddly worn. See pic below.


  2. #32
    Chris_2011 is offline Cadillac Owners Member
    Automobile(s): 93 STS
    Join Date
    Feb 2011

    Re: 2000+ Northstar Plenum Replacement steps

    Thanks very much for the tutorial! I replaced the intake plenum on my 02 SLS today. My car wasn't setting any codes but had a rough idle once the engine was warm.

    Quote Originally Posted by redfishsc View Post
    I ordered the Dorman plenum/gaskets from RockAuto, and the blue gaskets were NOT useable. They were the right "size/shape" but they would not seat firmly into the recess. Even if you managed to put them in and keep them there, they'd start falling out when you shimmied the intake back into place.

    I tried ONE of them, and since it didn't seat, I didn't touch the old gaskets. I left them in place. Cleaned them with WD40, cleaned the aluminum head where the intake bolts on with carb cleaner so that it was shiny again, and seems to be fine.
    I had the exact issue that you had with the Dorman gaskets - I also left on the original gaskets.

  3. #33
    notdel is offline Cadillac Owners Member
    Automobile(s): 04 Deville
    Join Date
    Mar 2012
    Lumberton, NC

    Re: 2000+ Northstar Plenum Replacement steps

    Quote Originally Posted by Chris_2011 View Post
    I had the exact issue that you had with the Dorman gaskets - I also left on the original gaskets.
    +1 on this tutorial. I replaced my plenum today and also had to replace the 90* elbow on pass side of intake manifold. As for the Dorman set from RockAuto, I had only one blue gasket not seat properly so used a little silicone RTV to hold in place. All is well. Runs like a Cadillac again!!

  4. #34
    B1G-AL's Avatar
    B1G-AL is offline Cadillac Owners Member
    Automobile(s): 1972 Eldorado, 2000 Deville, 2004 CTS, 2006 SRX
    Join Date
    Jun 2011

    Re: 2000+ Northstar Plenum Replacement steps

    I just did this and my Deville is running much better...however after doing the job my gas pedal is now sticky and does not smoothly press down like it did before. What could have caused this?

  5. #35
    MoistCabbage's Avatar
    MoistCabbage is offline Cadillac Owners 10000+ Posts
    Automobile(s): Crimson 2001 Seville STS, 1990 Seville (RIP)
    Join Date
    Sep 2010
    East Boston MA.
    Try cleaning the TB and make sure the throttle cable isn't binding.

  6. #36
    GetOffMyLawn is online now Cadillac Owners Fanatic
    Automobile(s): 2002.5 STS & 2012 XTS4; previously '96 '01 '03 STS
    Join Date
    Oct 2010

    Re: 2000+ Northstar Plenum Replacement steps

    Just got done with this procedure on my 2002.5 STS, idles so smooth again I had almost forgotten, and my PCM codes all went away. Here's a complete parts list with RockAuto links and my notes - everything is cheap, you might as well replace it all while you're in there. Tools were standard screwdriver set, ratchet set, and ratcheting wrench sets (you'll definitely want a 10mm ratcheting wrench for the 4 fuel rail bolts).

    Parts List:
    Useful Procedure Notes:
    • I'm not the only one who's found the Dorman gaskets that come with the plenum to be imperfect fits - might as well spend the extra $10 for the Fel-Pro and not worry about it
    • If you're careful and patient, you can leave the steel fuel rail connected - after disengaging a plastic clip that held the lines to the throttle body bracket and the nut for the rail itself, the assembly swung out of the way 90 degrees with no resistance or kinks. Total dis-assembly was much less intensive than the factory instructions - I was able to do it just disconnecting air/vacuum-type lines and electrical plugs, nothing liquid or mechanical.
    • Clean the throttle body from both sides, especially the plate edges and interior hinges - once you've got the intake off, you just have to unplug the MAP and another pigtail connector, and you can move the TB to the side of the engine bay (carefully) without having to unhook the throttle cables. I used a toothbrush to get it mostly spotless.
    • Plenum was oddly worn like Closet Boy's above, and some of the intake manifold gaskets had worn themselves completely flush/flat, as had the TB gasket - there was ample carbon buildup around each of those seals that deserved thorough cleaning - hand-cleaning the seal surfaces was by far the most time-consuming part of this procedure.
    • I took off the Overpressure Relief Valve on the intake manifold to clean it, as there was a very significant carbon buildup on that as well
    • I failed to find a reasonably-priced device (under $100) to accurately measure the super-low torque values specified by the factory instructions, so I very carefully winged it when reassembling - YMMV.

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