Tip and suggestions for replacing mini-cats on 2001 XJ

I replaced the mini-cats on my 2001 XJ over the weekend. This exhaust is more complicated and expensive than the earlier Jeeps, but doesn't have the manifold cracking problem. The exhaust components are flanged and bolted similar to earlier XJ's - no welds or pipe clamps. Depending on where you buy the mini-cats, the downpipe may or may not be included.

I had a heck of a time with the flange bolts at the exhaust manifold. There are 4 bolts with 15mm heads that thread into spring nuts that snap into the manifold ears. Because the cats are in the way and there is limited clearance, I found the only way to put a socket on the bolts was with a low profile 15mm socket and the shortest universal I had in my tool box. Even then patience and force were required to keep the socket square on the bolt. If anyone has any better ideas on how to do this, please let me know.

Also, I had a heck of a time just getting the mini cats in place while getting a bolt started. Three or four hands would be nice, but I managed. If anyone has any short cuts or tips, feel free to post them.

For reference, replacement bolts and nuts are

bolts - Mopar 6505754AA x 4
nuts - Mopar 6506546AA x 4

Also, the nuts at the downpipe flange were so badly rusted (probably because they are the lowest on the vehicle, my Jeep isn't badly rusted) that I had to cut them off. If you need to replace the bolts too, they are splined M10x1.5. Dorman sells a 3/8"-16 set of splined bolts that should fit (you will need two). Part number 03127. You can drive the old ones out with an air hammer if the pipe is held solid in about 30 seconds.

Thanks posting that. I might have to do this myself on my '00. Haven't ruled out the rest of the culprits yet though. Could find the bolt part#'s in my parts catalog but not the nuts. Now when you say nuts you mean the spring nuts right? And thanks for making it easy with the intermediate pipe bolts and nuts. Figured out would just find something at the hardware store that would work. You made my life so much easier, if I have to do this too, by posting these part #'s. Now I get get what I need before I do the job. Love having part #'s

Yes on the nuts

Mini-cat flange to manifold bolts - Mopar 6505754AA x 4
Manifold spring nuts - Mopar 6506546AA x 4

I would try a nut splitter on the downpipe flange nuts or some other non-destructive way to get them off if possible. It will be difficult to get them out with the pipe still on the vehicle. And if you need to remove the pipe, I would try down by the muffler rather than the cat. There is more clearance to get an impact on those and they should come right off. The bolts at the cat are smaller and more prone to breaking, especially if you don't have a torch.

md21722 said:

Yes on the nuts

Mini-cat flange to manifold bolts - Mopar 6505754AA x 4
Manifold spring nuts - Mopar 6506546AA x 4

I would try a nut splitter on the downpipe flange nuts or some other non-destructive way to get them off if possible. It will be difficult to get them out with the pipe still on the vehicle. And if you need to remove the pipe, I would try down by the muffler rather than the cat. There is more clearance to get an impact on those and they should come right off. The bolts at the cat are smaller and more prone to breaking, especially if you don't have a torch.

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Good to know. The only part of possibly having to do the cat that makes this bearable is the fact that I need a new muffler and tailpipe also. So I might just buy a new intermediate pipe, reuse the rear cat, and call it a day. And who knows. If my OCD kicks in I might even buy a new rear cat. Was thinking about a Borla Cat back exhaust for that but will probably go stock. Not like I have a stroker or anything. Just a 4 hole injector upgrade. Just out of curiosity what did you buy for the front cat? A Walker?

I used the dealer part. By the time I priced out a NAPA Cal Cat, the dealer part wasn't much more and included the crossover pipe. While I don't specifically need a CARB cat for Colorado, my girlfriend and I are talking of moving & I also wasn't sure how good the aftermarket ones are, so I paid the extra. The dealer part is an exact original. It seems that whenever I try to save a dime it costs me a dollar. YMMV. BTW, I've since found that a 15mm swivel socket works best. I used a Snap On FSUM15A. The Gear Wrench equivalent, etc may be just as good.

md21722 said:

I used the dealer part. By the time I priced out a NAPA Cal Cat, the dealer part wasn't much more and included the crossover pipe. While I don't specifically need a CARB cat for Colorado, my girlfriend and I are talking of moving & I also wasn't sure how good the aftermarket ones are, so I paid the extra. The dealer part is an exact original. It seems that whenever I try to save a dime it costs me a dollar. YMMV. BTW, I've since found that a 15mm swivel socket works best. I used a Snap On FSUM15A. The Gear Wrench equivalent, etc may be just as good.

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So you bought a CARB Dealer Cat? What did that run you? When you say it included the crossover pipe do you mean the intermediate pipe/downpipe? The one between the front cat and rear cat? Any chance you have a part #? I can pick up a Walker for CA emissions vehicles not registered in CA at Napa, which is me, for about $205 not including tax. I can pick up the Walker CARB version of that cat for about $400 at Napa. I did notice that the warranty is better on the Walker CARB one then the other one. If push comes to shove I just want to know what my options are. By the way thank you for all the info. Would be nice to know it and not need but I am not usually that lucky.

When I priced them, the NAPA CalCat was $630-700 and the dealer part was $782. The dealer part includes the middle pipe between the mini-cats & the rear cat.

Thanks for the info. I looked at your profile and saw you are from CO. Was a student at DU about a thousand years ago by the way. I understand why you bought a CalCat. Moving and all. I am toying with the idea of buying the Walker CalCat because of the better warranty. I am not going to lie though. That for CA emissions vehicles not in CA confuses me. It is not like they build CA emssions vehicles for other states. They just get sold in other states. Right? I mean it is either a CA emissions vehicle or not. So I am confused if I should spend the extra money.

Like I said my girlfriend and I are talking of moving, she likes the weather better, and I figured just be one and done... costed more but exact factory fit so I went with it. For $205 plus any extension fittings you might as just go with the non-CA parts. Once you do the job once its not a big deal. I could do it again this afternoon and not loose any sweat over it. My timing chain was within limits and I seemed to get better fuel economy after doing the change and I don't think it was all related to the switchover to summer blend fuel which happened by the time I put it back on the road. Seems to drive the same. No extra power or power loss. Just the same as my 01 has always done for me. I'd also say that like the manifold bolts you may not need new bolts & clip nuts. I had a heck of a time at first without the low profile/swivel sockets and didn't know what to expect so I just bought new fasteners. They are so close to the head that they really don't rust out or need to be cut, too hot, so you can probably re-use your existing fasteners if you go at it with the correct tools first time around. When you are done you should be able to fit your finger between the pan & minicat part. I think mine was tweaked some years ago and that's why it was resting against the oil pan. Probably when I drove over a mobile home trailer tire that was running towards me. I think it just bent the exhaust towards the pan as it bent the tie-rod & gas tank skid.

Sorry I edited my post. Befor kinda after you replied. Forgot you were moving.

It's all good. The hardest part for you will likely be removing the three nuts at the flange just below the minicats. If you can't get the nuts off I think you'll end up removing the whole pipe to drive them out. And if you need to do that, I still suggest removing the nuts from the muffler flange as they are easier to remove. That way you can drive them out with an air hammer. The air hammer won't work well if you try to use it with the pipe still in the vehicle because you have no way to hold it tight from vibrating which diminishes the effectiveness of the air hammer.