Curses for the factory pre-cats

Hey dudes-
Had to change my intake manifold gasket today on my 2001 4.0. Cali emissions

I even did the work at the jeep dealership I work at, air tools and everything. I did 6.5 hours of work and didn't finish.

-Sheared the studs on the downpipe
-Precats are so big, and the flanges are so big, that the middle 4 bottom bolts are basically impossible compared to a normal 4.0. (No pre-cats)
-The two collector flanges for the 2 piece header is a POS... mine was totally loose, likely contributing to my bad exhaust tick
-The two huge O2 sensors further block access to bolts
-Looked up the possibility of buying a new precat assembly, as mine is severely rusted- $1250. (CA smog)

I seriously wish I had a 99! (Or a 2000 with no cats up there.)

Sheared-

Untitled by Sean Mitchell 707, on Flickr

Before-

Untitled by Sean Mitchell 707, on Flickr

During

Untitled by Sean Mitchell 707, on Flickr

The horribly muddy, caked, heat baked and rusted pipes-

Untitled by Sean Mitchell 707, on Flickr

After cleaning the best I could-

Untitled by Sean Mitchell 707, on Flickr

And going back together.

Untitled by Sean Mitchell 707, on Flickr

Still not finished, as I ran out of time when we had to close the shop. Yay! More work tomorrow.

Columbus

The pre-cats are a nightmare. I was getting low efficiency cat converter codes about a year after I bought my Jeep. Luckily, I live in CT so I was able to replace them with a Walker set-up for about $300. They have been fine since, but the pre-cats sure make 0331 head swaps a bit more of a PITA than earlier heads. Combine that with the fact that I live in the salt belt and they become a huge headache.

Got tired of replacing donut on my '79 258 cu. in. J. Cherokee Mod. #17 between exhaust man./down pipe as per the rusted nuts/studs there.., so I drilled that issue out, and replaced with S.S. nuts/bolts. Worked great. Seems that while you are at it, (it might someday come in handy), to install a engine block coolant heater into one of your freeze plugs at this point in your work. Seems the various sites that discuss the best year via surveys have the consensus that the '99 XJ is all around the best, depending on the set-up, and options package, blah, blah, blah.

You all don't have a wire wheel motor, or hand held units to remove all of that slag? There are exhaust tapes, and even some high temp. paints that might enhance your manifold project.., sheesh.

Do you have any on the shelf OEM parts for us RENIX folks there in your parts department? Not chinese oem parts, but real parts? IF you do, pm me.., that is.., if you are going to stay there at that dealership. Think about it.., you could charge us a handling fee.:idea:

If you want to purty up the manifolds, set up an electrolytic derust tank and cook them for a day or two, then use a manifold dressing or paint on them.

For the hardware, rather than going all stainless I would use stainless studs/bolts and brass nuts. Studebaker used brass nuts on their manifold studs and when misguided mechanics haven't replaced them with steel, it makes disassembly so much easier. Even if the studs have rusted to the point where you can't unscrew the nuts, you can just blow them off with a torch, then rethread the studs with a die or replace as appropriate.

N8N_99xj said:

If you want to purty up the manifolds, set up an electrolytic derust tank and cook them for a day or two, then use a manifold dressing or paint on them.

For the hardware, rather than going all stainless I would use stainless studs/bolts and brass nuts. Studebaker used brass nuts on their manifold studs and when misguided mechanics haven't replaced them with steel, it makes disassembly so much easier. Even if the studs have rusted to the point where you can't unscrew the nuts, you can just blow them off with a torch, then rethread the studs with a die or replace as appropriate.

Click to expand...

Me thinks the Cat internals won't take kindly to the electrolytic tank chemicals.

No chemicals, just water and washing soda. But I was assuming separating manifolds and cats before cooking them...

Look into some flex head gearwrenches or possibly these miracle workers: http://www.sears.com/craftsman-9-16...0914572000P?prdNo=28&blockNo=28&blockType=G28

Not sure either one will solve your problem, but they might.

Glad I found a 99. That looks like a nightmare.

kastein said:

Look into some flex head gearwrenches or possibly these miracle workers: http://www.sears.com/craftsman-9-16...0914572000P?prdNo=28&blockNo=28&blockType=G28

Not sure either one will solve your problem, but they might.

Click to expand...

Nope, required a standard depth 3/8ths drive 14mm. Then a universal joint, and 2 extensions. But since the flex drive likes to hang downwards, you can't place the socket on the bolt from the top. So I would have to get on my back, slide the socket over the bolt, and then set the extension just right so I could jump back up to the top of the engine bay, and either put my air ratchet on it, or a ratchet. Slow, SLOW work. Horrible.

I finally got it back together. Took me just another 45 minutes. I retorqued all manifold bolts, then installed all the crap on top.

It runs pretty awesome now. No noises. I just need to do another torque check now that it has gone through a heat cycle.