Also remember the lower O rings on the injectors need to seal vacuum. A leak there might seem like the manifold cause it's like, an inch away. I wouldn't expect that to whistle though.

 

My noise was reduced and my idle was a bit smoother, so I guess I found my problem.

Looks like I have a gasket to replace.

Thanks again for the pointers.

 

yes it turned out to be the intake gasket ($430) later caz i couldnt figure it out...

 

With the engine cold, start at the middle bolts and work toward the ends and snug them all up carefully. May end up not needing to replace the gasket.

 

Thanks for the advice, but no such luck. Aside from the one bolt I was able to turn in 1/8th turn or so, I can't budge any of the other bolts.

I'm mulling over replacing the gasket myself or taking it to the stealership. I was quoted $421 which is about the same as Snwboarder673 reports paying.

 

That's some major $! Why the dealer? Even in my little town we have more than three or four guys making an honnest living twisting wrenches. (doesn't include me). It IS a tad involved, You get into lots of stuff. It's a good time to check stuff like wiring, vac. lines, motor mount, PS pump and belt come off. ect. (that might end up being the starting price)

You're are positive it's the manifold? You found a spot you can spray a little shot of starting fluid and the engine sound changes, AND you are sure it's not a lower O ring on an injector?

 

Well, no such luck there either. I live in a resort/retirement area and I think if there was a shop that wasn't trying their hardest to rip off tourists and retirees that the owner would have been provided with cement overshoes by the competition by now .

Compared to the $1249 intake gaskets cost for my wife's Century (3 years ago)(I didn't even consider wrenching on that thing), $421 seemed like a bargain.

However I am leaning towards doing it myself because after 5 months/1000 miles of owning this thing, I have decided I really like it and will probably eventually have to rebuild it or put a crate motor in it as it has 156,000 miles on it. May as well get used to working on it now.

I also have been reading about changing the injectors to Neon 784's. After looking at all the crud on the old injectors in a pictorial "how to", and guessing that due to my high mileage that mine are probably worse, it looks like a good idea to do both jobs at the same time. I think cleaning out the holes in the intake where the injectors go will be a lot easier with it removed.

 

156k miles really isn't a whole lot considering some of these guys have put over 500k on their original engines

 

Well, you could make some phone calls anyway. I might be a little out of touch. Mostly a wild guess, but with all the right stuff on hand a guy who has done it before might do it in three hours. Just a guess. I did mine a few months ago and spent a weekend on it.

I'm no help on the injectors. I put 703's in my 90, but those years came with notoriously crappy injectors. If the 2000 has single hole, you might benefit by going to four. (the day I finished with mine, I heard they came out with six hole in something) Anyway you might ask notop...(46?)

Btw, you have the 0331 head, (also notorious). You really don't want to blow a hose and overheat. (I guess that "tupy" mark would be under the oil cap...........V)

"The heads that had trouble were the early #0331 heads (1999-2001WJ/TJ, 2000-2001XJ) before they were revised in late 2001 (revised heads have the "TUPY" foundry mark.) "

I guess there is no single part of the manifold job that is too tough. My header pipe flange bolts where easy, but they often can be a real hassle. At least if a stud brakes, it's on the manifold you are taking off. I was lucky the manifold bolt I broke off in the head was up front where I could drill it.

I changed mine because I had a vacuum leak AND exhaust was blasting out at the rear. Then I found my vacuum leak was an injector O ring. Mostly at least.

And yea, ^X2. I'm running fine at 264K. I actually got 19 on a Hwy. trip recently. Big storm, 6 hrs of rain. I'm wondering if the humidity let my Renix ECU advance the timing a bunch. Anyhow, that 4.0 IS amazing!

 

Changed mine out last week in the driveway with basic hand tools. The worst part if it all is trying to access the bolts on the bottom side. It takes a variety of sockets and extensions, all of the bolts are 14mm but you will need both deep and shallow sockets.

The basics of getting it done:
Remove the electric fan (2 8mm bolts) to have better access to the power sterring pump bolts
Loosen and remove the serpentine belt
Remove the 3 bolts that mount the pwr steering pump to the intake, 15mm
Remove the airbox, 2 bolts and 1 nut 13 mm and have some long extensions to make it easier
Disconnect the throttle cable and trans kickdown cables from the throttle body
Start removing the bolts for the intake/exhaust manifolds, 8 bolts and 2 nuts all 14mm. The nuts are on studs at the very front and rear of the exhaust manifold. the back one requires profanity to get to it. Ok profanity doesn't help it come loose but flowers won't either and we have to stay manly.
The exhaust pipe will limit how far the manifold will move away from the head but it does not have to be removed.
After everything is loose pull the intake back away from the head and then work the exhaust manifold back away from the head to access the old gasket. the rear of the exh man will not come away far enough to get the gasket out without a little persuasion form a big pry bar. Just don't damage the surface of the aluminum head. It only takes a tiny gap to slide the gasket out.
Clean the surfaces of the kead and manifold with some brake cleaner prayed on a rag.

Reinstallation:
Using the prybar to again create a small gap between the exh man and the rear locating stud, slide the end of the gasket in and onto the stud.
Lower the front end of the new gasket and slide it onto the front locating stud.
Push the exh man back into place on the locating studs and reinstall the front and rear nuts finger tight to hold the manifold and gasket in place.
Position the intake and start installing the bolts.
Once all of the bolts are in place and finger tight then it is time to start torqing them down in sequence.
Looking at the intake from the drivers side fender the bolts are number as follows.
1 - top of intake, 3 bolt from the front 24 ft/lbs
2 - bottom, 3rd from front 24 ft/ lbs
3 - bottom, 2nd from front 24 ft/lbs
4 - bottom, rear bolt (not the nut) 24 ft/lbs
5 - bottom, front bolt (not the nut) 24 ft/ lbs
6 - front nut 23 ft/ lbs
7 - rear nut 23 ft/lbs
8 - top, 2nd from front 24 ft/lbs
9 - top, rear bolt 24 ft/lbs
10 - top front bolt 24 ft/lbs

Reintstall everything else the same way it came off and you should be good to go. With the proper tools on hand it should take the first time installer around 4-5 hours. the most time consuming part is constantly switching different length extensions and socket to access the bolts.

 

Nice write-up!!

 

X2^. Of course it's a little more involved to get it in a bench. With a swivel socket on about 18 inches, (or more), of extension that rear nut actually isn't as bad as the rearmost bolt underneath. No big deal in any case.

 

And make darn sure the intake manifold is fully seated on the locating dowels before tightening it up.

 

It sounds like the same problem I have. My question is, is there a test you can do to see if air is coming out from the manifold bolts being loose? Besides being annoying, will that whistling sound cause any damage?

 

It isn't air coming out, it's air being sucked in. Spray the suspect area with throttle body cleaner. When you hit the leaking area the idle speed will change.