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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Any vacuum leak can set mixture codes - cracked connectors/elbows, plastic pipes or the plenum. Hard to go back and isolate what might have been the problem.
 

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2002 SLS
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Re: 2000+ Northstar Plenum Duct Replacement steps

Much thanks for this procedure.
2002 Seville SLS has been fixed!
Had to favor drivers side to remove manifold to avoid PVC tube snag.
Other than that , all went as you described.
Total time about 3 1/2 hrs, cautious and real slow during dis-assembly, re-assembly went quicker, included clean-up time.
Local Cadillac dealer for in-stock plenum (MSRP) , local auto parts for gaskets, $16.00.
Thanks again.
 

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'04 DeVille
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71 Posts
On an '04 DeVille, is there anything that is also holding the rear fuel rail in place? The front one popped off without too much effort. I can't get the rear one to budge. :(
 

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'04 DeVille
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Finally got it. It took two of us. Can't believe how much force it took.

Wow, what a difference!

Now realize that although it has only been the last few weeks that it has been running obviously rougher, it was definitely not right from when I got it. If only I hadn't transposed P0174 with P0741. :(

Thanks for all the great info in this thread!
 

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Seville
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1 Posts
Joined just to thank everyone on this thread. Completed job yesterday. Saved so much Aggravation and time by ordering the felpro intake gaskets, as the one s that came with the plenum were worthless. Runs great, wish I would have searched this site before replacing coil pack and maf sensor, but still well below dealership. I would also recommend replacing the dirty air intake tube on left side. I purchased one at the dealership for $17. Wasn't cracked until I moved it to check a little to far and it ripped. Nonetheless glad I replaced it as it was brittle and would probably needed it soon. You need special pliers , mine didn't arrive with my parts so I winged it with needlenose.
 

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2000
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4 Posts
Can someone tell me where the other end connects to? I replace a starter on my mom's 2000 this evening. I just missed this vacuum line on the pass side of the plenum. I can't find a vacuum hose/line anywhere. I know the 90 deg goes on the intake/plenum, but where in the heck does the other end hook up to.

Borrowed the pic from a earlier post...



Thanks for any help.

That is a nice place to hide a starter...

Smitty

40_zpsta89tp5n.jpg
 

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It's not the PVC line. There is another port that is near the PVC port in the Plentum. It is towards the bottom of the plentum (pass side, lower rear) by the power steering pump.

Thanks Smitty
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Re: 2000+ Northstar Plenum Duct Replacement steps

2000 What? Deville, Seville, Eldorado - it makes a difference in quite a bit of advice.

Here's the front (passenger) end of a 2000 - 2004 Northstar intake manifold. Only one vacuum connection: The PCV dirty air line, way inside the center tunnel.

.............and the vacuum diagram for the 2000 and later engine.

Maybe, just maybe, depending on car/model, that blanked off cap #13 might be used for something. Maybe a holdover from the older vacuum-operated HVAC stack doors ? Firewall hose/pipe ?

Click a thumbnail to enlarge, use your browser <-- to back out.
 

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Re: 2000+ Northstar Plenum Duct Replacement steps

2000 What? Deville, Seville, Eldorado - it makes a difference in quite a bit of advice.

Here's the front (passenger) end of a 2000 - 2004 Northstar intake manifold. Only one vacuum connection: The PCV dirty air line, way inside the center tunnel.

.............and the vacuum diagram for the 2000 and later engine.

Click a thumbnail to enlarge, use your browser <-- to back out.
Thanks for those pictures. I have search all over mom's 2000 Deville and could never find what that port(the one capped off) was for. I did stop by my local dealer and the parts guy gave me a pic of a parts break down. It showed a hose coming off that plugged port adding to my confusion. I put a new cap back on the extra vacuum port and will call this job done.

Thanks for the help!!

Smitty

Here is the picture's the dealer gave me.. It is part number 567... Nothing like that on this car..

hose1.jpg
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Re: 2000+ Northstar Plenum Duct Replacement steps

Question: Does the HVAC system - temperature and mode doors and blends - still work? That diagram shows the vacuum hose and one-way check valve that supplies operating vacuum to the ??? pre-2000 ??? HVAC stack.

Am I misinterpreting your pictures in Post #46 - your Deville does NOT have this right angle vacuum connector ? If it does not, then you're OK - the 2000 and later HVAC doors are controlled by electric actuators, not vacuum. That diagram shows a pre-2000 Northstar line drawing - the early engine beauty cover is the giveaway.

"borrowed the pic" may be the problem - these engines underwent many changes over the model years. Unless we stay within the narrow confines of each generation of re-design we all stumble over small details.

Engine beauty cover - here's what a 2000 and later should look like - disregard the air intake and coolant surge tank - Deville is different from my Seville. Same as yours - look closely ? Same oil fill cap (5W-30) and ignition coil cassette - gray ?
 

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Yes, cover look just like that. I guess what puzzled me was there was a small piece of rubber on the plugged hole on the plentum. But the end was torn off. So I was thinking it was not a plug or cap and just a vacuum hose that was broken off..

I think the mystery is solved.

Thanks Sub for taking the time to help me.

Smitty
 

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2003 Deville
2003 Deville, 2003 Passat GLX, 2003 Silverado 2500HD
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69 Posts
Thanks to all the guys and gals that created and added to this thread...made the intake gaskets / plenum gasket replacement a breeze. Takes a bit of time to clean all the various gasket mounting faces, parts and such, but guaranteed a dealer and/or local shop wouldn't take that kind of time and energy to ensure a thorough job like we as owners do. Its all about pride in your ride!!
 

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2001 STS
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18 Posts
Big thanks for posting this, mrvspitbulls. Cleanliness and care throughout your described procedure yielded a very nicely running car - a new to me '01 Seville STS (123K miles) that came from Copart for $125 that started but barely ran - until I did this fix. The P00171 and P00174 codes cleared immediately, and the car now runs like a striped a$$ ape. I vacuumed often and used clean rags for every swipe. I used a brass brush to carefully clean up old marks around each intake port. I had to thoroughly clean oil off each manifold gasket seat and then use a little spot of gasket maker to hold each cheesy intake manifold gasket in place. Next time, I'd spend the extra money for the tightly fitting Fel-Pro gaskets, for sure.
 

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Re: 2000+ Northstar Plenum Duct Replacement steps

Thanks Rob for a fantastic tutorial on replacing the plenum gasket, the photos are such a great help! Many, many thanks!
 

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So I've been lurking on this site for awhile now as I have 04 DTS. I found the Plenum gasket was leaking so I googled it and here I came again, anyway. I managed to pull the old Plenum gasket out ripped in a few places. I bought the $20 Dorman gasket set and figured wth., I'm going to try to re install it without pulling the intake. So I removed the two lines from the fuel rail and a few other vac. lines and pigtails. I removed the clamp from the new Plenum, rolled the bottom of it back slid it down where it belongs then stuck a few fingers through the housing between the Plenum a Throttle body and pulled back on the bottom of the gasket, tapped on the bracket holding it and it slide right in place. It was a breeze. I think if I had soaped it up first it would have slid in easier. Car runs great now! This site has helped me a few times so I thought I'd share, for twenty bucks I figured why not risk the gasket. The worst part was installing the clamp back on the Plenum gasket.
 

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Hey Rush, thanks for this!
I too have a 04 DTS.
I'm very interested in trying what you did but I'm a NOOB! Or BECAUSE I'm a NOOB and it seems like much less intrusive.
I'm thinking of buying the OEM part just in case it helps having to do it less often.
Would you be able to, please, explain a little better what you DID have to remove?
Ideally with a (or some) pictures pointing at the "two lines from the fuel rail and a few other vac"?
Can big fingers do it?
How did you do the worst part: "installing the clamp back on the Plenum gasket"?
Anything else that would help?
Thanks,
Cat
 

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2005 DeVille
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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. :highfive:

Hope this helps Thanks for Everything
Great instructions! All done in 2 hours, and the only real difficulty was getting the blue gaskets to stay where they are supposed to. I lubed them with oil from the manifold and after warming in the sun, stayed where they should. The front drivers side manifold bolt was a pain, but all in all I surprised myself! Great instructions!
 
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