2000+ Northstar Plenum Replacement steps
Cadillac
 

Cadillac Forums | Help Us Help You | Advertise | Cadillac Parts | Cadillac News | Cadillac Classifieds / (Old System)

Cadillac Technical Archive | Cadillac Dealers | Cadillac Reviews | Cadillac Dealer Reviews | Cadillac Vendors

CadillacForums.com is the premier Cadillac Forum on the internet. Registered Users do not see the above ads.
+ Reply to Thread
Page 1 of 3 1 2 3 LastLast
Results 1 to 15 of 36
Like Tree14Likes
Cadillac Tech Tips - How to fix it Discussion, 2000+ Northstar Plenum Replacement steps in Item Specific Cadillac Discussion; First I want to say Thanks for all the help and tips from this Great Board !!!! This is how ...
  1. #1
    mrvspitbulls's Avatar
    mrvspitbulls is offline Cadillac Owners Fanatic
    Automobile(s): 05 Cadillac STS
    Join Date
    Apr 2008
    Location
    KC
    Age
    33
    Posts
    137

    2000+ Northstar Plenum Replacement steps

    First I want to say Thanks for all the help and tips from this Great Board !!!!

    This is how I did this procedure...

    1) Removed gas cap

    2) Pop hood remove Top cover and bleed off pressure from fuel rail pressure relief valve

    3) Take off top of air box and air tube closest to tb, unplug maf plug

    4) Just loosen the 10mm nut that holds fuel lines down and undo lines from the black clip on top

    5) Unclamp the top line on the coolant jug (a little might come out) Lay it to the side

    6) In front just unhook one vacume line and unplug the plug going into coil pack

    7) In back just unhook the vacume lines that are in the way (I think it was 4 or 5 of them) and unplug the plug going to that coil pack

    8) Take the 4 10mm bolts out that hold the fuel rails down

    9) Carefully pull up on the fuel rails evenly, they will all pop out together, pull them straight up together you'll have to wigle it around a little but you can get enuff room to work

    10) Take the 10 10mm bolts out of the manifold

    11) Loosen the plenum bolt (The strap clamp) there are also 3 10mm bolts that hols the plenum in. You'll see them from driver side, pretty easy to get to

    12) Hold the fuel rails up out of the way and start from passanger side and lift the manifold up and out

    13) Turn manifold over replace all 8 Blue gaskets (most local parts stores have these $15-$20 for a set of 8 )

    14) Take off old plenum ( I used a big screwdriver and pryed up around the sides)

    15) Put your $30 new plenum on (the same way the old one came off)

    16) I took my shop vac and vacumed out everything so nothing would fall in engine, then just wiped it down with old shirt rag

    17) Hold fuel rails back up and drop the manifold back into its home

    18) Reasemble everything you just did. On the manifold bolts just start in the middle and work your way around, don't tighten till there all hand tight.

    Thats pretty much it. Of course inspect everything as you go.

    When i did this job all 10 of my manifold bolts were loose like all of them were just hand tight. I thought that was crazy..

    The whole job took me about an hour and a half. because i have never done this before. Stealership probably can do it under an hour. Started it up and it runs perfect.

    Hope this helps Thanks for Everything
    Attached Images
    power007 likes this.

  2. Remove Advertisements
    CadillacForums.com
    Advertisements
     

  3. #2
    Submariner409's Avatar
    Submariner409 is offline If it won't run, stick on fender vents
    Automobile(s): 2002.5 F55 STS/65500mi, 2004 Ford F150 SuperCab4x4
    Join Date
    Feb 2006
    Location
    MD Eastern Shore - Kent Island
    Age
    74
    Posts
    45,512

    Re: 03 Deville DTS Plenum Replacement steps

    Good post - the factory torque on those manifold bolts is light: 89 in/lb., or 5.5 ft/lb.

  4. #3
    tateos's Avatar
    tateos is offline Cadillac Owners Connoisseur
    Automobile(s): 1997 ETC (GAVE TO STEPSON 2011), 2000 DTS (RIP)
    Join Date
    Jul 2007
    Location
    FOUNTAIN HILLS, AZ
    Age
    58
    Posts
    1,711

    re: 2000+ Northstar Plenum Duct Replacement steps

    Just curious - can't you leave the injectors and fuel rail attached to the manifold and R and R it as an assembly? You can on a '97 - maybe 2000+ is different?

  5. #4
    andrewgrahamwebb is offline Cadillac Owners Member
    Automobile(s): 2000 sts
    Join Date
    Feb 2009
    Age
    31
    Posts
    14

    re: 2000+ Northstar Plenum Duct Replacement steps

    guys, whats the part number for the plenum?

  6. #5
    charniw is offline Cadillac Owners Member
    Automobile(s): Aurora 4.0
    Join Date
    Jun 2009
    Age
    57
    Posts
    1

    re: 2000+ Northstar Plenum Duct Replacement steps

    Plenum: 12555840

  7. #6
    JimHare's Avatar
    JimHare is offline Cadillac Owners Connoisseur
    Automobile(s): 01 Eldo ETC, 02 Deville SOLD!
    Join Date
    May 2004
    Location
    Salem, NJ
    Age
    61
    Posts
    1,815

    re: 2000+ Northstar Plenum Duct Replacement steps

    I'm halfway done my job at the moment - taking my time, and being careful not to break any plastic..

    One thing I noticed - my fuel lines are stainless steel, and they're held on by a small bracket just to the right and down off the TB. The rails would not come up out of the way until I managed to get the rail bracket loose, which of course involved removing a clp around a big ol' cable next to the fuel lines, then moving the cable out of the way so I could get a deep-dish socket (13mm?) on the nut holding the rails. Once the rails were loose, I could move them up and out of the way from the other side of the car, and then lifted the manifold out completely.

    The plenum was indeed cracked.

    Have attached another pic of the fuel rails that I had to jimmy out of the way. Anyone with a newer NS will probably have these rails to work with.

    Tomorrow after work I'll be picking up the intake manifold gasket set ( I forgot to order one when I ordered the plenum. Did remember the TB gasket though, which oddly enough cost more than the plenum did.) I'll be putting things back together and hope to finish tomorrow night or Saturday morning if the weather holds.

    As others have noted, this is not a difficult job. Getting the steel fuel lines loose took me longer than I thought, because I tried to think my way through removing the manifold without doing it - but there is no way to move the front and rear fuel lines if that bracket isn't loose. And I didn't want to kink any thing...
    Attached Images

  8. #7
    holgatelbi is offline Cadillac Owners Member
    Join Date
    Mar 2006
    Posts
    9

    re: 2000+ Northstar Plenum Duct Replacement steps

    2000 Seville SLS Plenum boot & intake seal replacement.
    Getting 0171 & 0174 lean codes and 0101 MAF code.

    Stealership wanted $560 & said it was a 4 hr job. Took me 2-1/2 going slow & $73 for parts (8) 12557497 & (1) 12555840

    I have to thank all that have contributed to this thread & the regulars that help us weekend warriors all the time. I followed MRVSPITBULLS directions almost to a tee & had zero problems with this repair. And I'm a carpenter with just enough tools to get me in trouble. Working in a stone driveway & not a garage it took me total of 2 1/2 hrs. That was going slow so not to screw up this marvelous piece of engineering called the NORTHSTAR.

    The only changes or deviations I made were the following:

    1. I blew off the whole area with the air hose prior to any disassembly, hoping to avoid dirt getting where it shouldn't.
    2. Move step #5 up to step #2.5. I fought to remove airbox & tube (I'm a carpenter) w/o removing Radiator overflow.
    3. Per Jim Hare - loosening the bolt that holds the metal fuel lines near TB helps give you more movement in fuel rails.
    4. I found an extra plenum bolt sleeve precariously sitting right next to an intake port when I removed the plenum. I checked to see if I had dropped it. But, I had 10 bolts & 10 sleeves in my hold cup. Sleeve must have come from the factory. Had it fallen into the port while I removed the plenum - I would have never known it & probably would have blown the head apart.
    5. Per SUBMARINER409 - oil on injector "O" rings helped reassembly.
    6. Not trying to make me seem like a dumby, but was I surprised to find a starter buried under all of this mess!!!!! Should I have replaced it while I was in there? I didn't. Car has 83K on it & never (touch wood) had a starter issue.
    7. A good cleaning of all mating surfaces & vacuuming out of all ports before reassembly.

    That's about it - pretty uneventful procedure - thank God. Runs smooth & strong again.
    And thanks again for all the help this forum provides.
    Ashtrayhead likes this.

  9. #8
    Submariner409's Avatar
    Submariner409 is offline If it won't run, stick on fender vents
    Automobile(s): 2002.5 F55 STS/65500mi, 2004 Ford F150 SuperCab4x4
    Join Date
    Feb 2006
    Location
    MD Eastern Shore - Kent Island
    Age
    74
    Posts
    45,512

    re: 2000+ Northstar Plenum Duct Replacement steps

    Here's another heads-up: the "plenum"-to-throttlebody mounting plate has 3 nuts which are welded to the plate. You must remove the 3 long bolts which go through the throttlebody casting in order to remove the entire plenum - a while back someone in CF tried to loosen the nuts and had a hell of a time.

  10. #9
    AMGoff's Avatar
    AMGoff is offline Cadillac Owners Connoisseur
    Automobile(s): '03 Seville STS, '89 Eldorado, '89 Grand Wagoneer
    Join Date
    Aug 2007
    Location
    South Jersey
    Age
    41
    Posts
    2,153

    re: 2000+ Northstar Plenum Duct Replacement steps

    Fantastic write up... Ended up having to replace mine last night and did so easily after a single glance of your breakdown. The whole process took about an hour - including all 8 upper intake seals and a vacuum line (preventative measure) and would have been done even quicker if I weren't so pedantic about cleaning all the various bits. ;-)

    Two small notes from my own experience... First, I found no need to disconnect the coolant line from the tank - it just wasn't necessary. Second, with the three plenum bolts pulled back a ways through the TB, I found the manifold was much easier to lift out from the driver's side rather than the passengers'.

    Nonetheless... This was most helpful

  11. #10
    Submariner409's Avatar
    Submariner409 is offline If it won't run, stick on fender vents
    Automobile(s): 2002.5 F55 STS/65500mi, 2004 Ford F150 SuperCab4x4
    Join Date
    Feb 2006
    Location
    MD Eastern Shore - Kent Island
    Age
    74
    Posts
    45,512

    Re: 2000+ Northstar Plenum Duct Replacement steps

    Some manifold and plenum pictures for 2000+ reference. Click my username, open the profile. 2 albums, 6 pages of 2000+ Northstar parts - many of the entire intake system.

  12. #11
    Ghostsoldier's Avatar
    Ghostsoldier is offline Cadillac Owners Fanatic
    Automobile(s): 2000 Eldorado ESC; 1974 Dodge Monaco 440 Police package
    Join Date
    Apr 2009
    Age
    51
    Posts
    190

    Re: 2000+ Northstar Plenum Duct Replacement steps

    Here's my take on the plenum gasket replacement. Keep in mind I don't know all the technical names for certain items, but I've tried to supply enough pics to make this easy for the common car guy doing his own repairs....my thanks to mrvspitbulls for his tutorial, which I used and modified a little for this tutorial:

    1)Remove the gas cap.

    2)Remove top cover and bleed off pressure from fuel rail pressure relief valve.



    If needed, this is the time to spray and clean the top of the engine to keep debris from falling inside the block/intake/injector holes.

    3)Loosen clamp on overflow tubing and remove hose. Loosen nuts on clamp studs, pull tubing up and fold tube/hose to front of engine.






    4)Unplug MAF sensor plug. Remove clamp at the throttle body (TB) throat. ‘Snap’ out the air box and air tube assembly, and lay aside.










    5) You should have unobstructed view of the TB.


    More to come....

    Rob

  13. #12
    Ghostsoldier's Avatar
    Ghostsoldier is offline Cadillac Owners Fanatic
    Automobile(s): 2000 Eldorado ESC; 1974 Dodge Monaco 440 Police package
    Join Date
    Apr 2009
    Age
    51
    Posts
    190

    Re: 2000+ Northstar Plenum Duct Replacement steps

    More....

    6) Remove front valve cover vent hose and rear PCV valve and hose; unplug the coil packs (beware the safety clips—I broke mine).








    Remove the four 10mm studs holding the fuel rails to the intake manifold (the same ones also hold the overflow tube in the front)




    More to come....(this thread limits me to 15 pics per post)....

  14. #13
    Ghostsoldier's Avatar
    Ghostsoldier is offline Cadillac Owners Fanatic
    Automobile(s): 2000 Eldorado ESC; 1974 Dodge Monaco 440 Police package
    Join Date
    Apr 2009
    Age
    51
    Posts
    190

    Re: 2000+ Northstar Plenum Duct Replacement steps

    7) OPTIONAL STEPS: I chose to remove the TB to clean it, because mine was filthy…you may not have to do this, and can skip to Step 8. But if you choose to do so, it is a good time to do it while everything is disconnected. I unplugged the orange doohickey….



    …the throttle cable….


    …the vacuum line….




    …the top hose…


    ….and the electric wire cable from the TB body and bracket, to get extra work room and to avoid breaking anything important.



    I removed the 3 bolts holding the TB to the engine…






    You can see the welded nuts on the plenum gasket here which do not move.


    I removed the long bolts, and pulled the TB away from the block.


    You can clean or replace the rubber TB o-ring at this point (I just cleaned mine)


    I cleaned the TB inside and out with carb spray and a rag, as well as the block mounting area.



    More to come....
    Rob

  15. #14
    Ghostsoldier's Avatar
    Ghostsoldier is offline Cadillac Owners Fanatic
    Automobile(s): 2000 Eldorado ESC; 1974 Dodge Monaco 440 Police package
    Join Date
    Apr 2009
    Age
    51
    Posts
    190

    Re: 2000+ Northstar Plenum Duct Replacement steps

    8) Loosen the 13mm bolted clamp that holds fuel lines down and undo lines from the black clip on top. I accidentally broke the plastic clip (no big deal), and removed the bolt holding the fuel lines secure.



    This was the hardest part of the job for me, because that bolt was directly under the taut wiring harness, and it was a pain to get the wrench in that space. It has to be loosened, though, or you won’t be able to raise the fuel rails high enough to lift the intake free.







    9) Be sure to unplug the vacuum line from the rear of the intake; I forgot to, and broke the nipple off…after a little repair work, I fixed it, but it would have been avoidable had I thought to unplug the hose.





    10) Carefully pull straight up on the fuel rails evenly, and they will all pop out together; you may have to wiggle it around a little, but you can get enough slack in the rails to work the intake out from under them.





    11) Remove the ten 10mm bolts from the manifold.


    You should now have loose fuel rails, and an unbolted plenum gasket and intake manifold.


    These are the bolts you should have (right-to-left): 1 fuel rail clamp bolt, 3 TB bolts, 10 intake bolts, and 4 fuel rail clamp bolts.


    12) Hold the fuel rails up out of the way, and starting from the passenger side, break the intake seal bonds and lift the manifold up and out from the front of the engine.


    13) Now is the time to check the starter connections and that doohickey plug; also, cleaning the intake valley (with a shop vac) and the intake port seal surfaces (with a rag) is a good idea.


    More to come....
    Rob

  16. #15
    Ghostsoldier's Avatar
    Ghostsoldier is offline Cadillac Owners Fanatic
    Automobile(s): 2000 Eldorado ESC; 1974 Dodge Monaco 440 Police package
    Join Date
    Apr 2009
    Age
    51
    Posts
    190

    Re: 2000+ Northstar Plenum Duct Replacement steps

    14) Turn intake manifold over, remove the 8 old seals, clean the mounting surface, and press-in all the new blue rubber gaskets; be sure to align the small tabs on the seals in their appropriate intake manifold slots.







    15) Remove the old plenum by loosening the clamp, then use a screwdriver to pry the old plenum gasket off of the intake…it can be really stuck tight (use carb spray).




    Clean the intake throat, and inside the chamber now (if needed).

    16) Here’s the source of the P-codes and crappy performance…a huge, 3” tear in the bottom of the old plenum gasket (which I understand is quite common in these engines), sucking in extra air.





    17) Install your new plenum to the intake (it goes on the same way the old one came off); leave the clamp loose for adjustment to the TB/block during re-installation.







    18) Hold fuel rails up again, and push the manifold back into its home; install the manifold bolts by starting in the middle, and working your way around and outwards. Don't tighten them snug until they are all hand-tight.



    19) The rest of the re-assembly is the opposite of removal….just be sure to reconnect everything you’ve taken loose or removed, check and double-check all your bolts and connections.

    20) Clear the PCM codes and start the engine. Your idle should be back to normal (750-800 rpm), and there should be no surging or skipping. Congratulations….you’ve just repaired the faulty plenum gasket on your Northstar!

    Here’s a shot of the parts I used for this repair: The plenum gasket and the Felpro intake seals.





    And there there you have it, my shade-tree tutorial with photos....I hope this helps others with the same issues!

    Rob
    eyeu81, eyeu81, Doola36 and 9 others like this.

Quick Reply Quick Reply

Register Now

Please enter the name by which you would like to log-in and be known on this site.
If you do not want to register, fill this field only and the name will be used as user name for your post.

Please enter a password for your user account. Note that passwords are case-sensitive.

Please enter a valid email address for yourself.

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Bookmarks

Cadillac Posting Rules

  • You may not post new threads
  • You may post replies
  • You may not post attachments
  • You may not edit your posts
Read about Lincoln | Buick | Kia Forte Forum
Need products for your Cadillac? Check out your options at the links below:

custom floor mats | Cadillac Chrome and Black Chrome Wheels | window tinting