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One day I started having issues with my exhaust sounding like the MO suddenly had a big V8 dropped in it. Then it got much worse, so I was pretty certain it was the exhaust manifold. Turns out I was right. But the big problem was it was the rear manifold on my AWD MO.



After searching a few forums and not finding any info for replacing the rear exhaust manifold I decided to post my work to help someone else. From what I read a lot of people described this job as being a huge PITA, but overall I didn't think it was too bad. It did take me about 8 hours of work but with some help and better tools I think that could be cut down dramatically. Also I dont have impact guns or many power tools so that did hinder me a bit as well.

Tools needed:
Jack stands
Metric regular and deep sockets with a 3 piece 1/2" extension set.
Screw drivers
22mm open box end wrench for oxygen sensors (or special ratchet)
Regular pliers and needle nose
Allen wrench set

I started by removing the air intake manifold and top of the filter box to be able to access the upper backside of the engine. There are some much better tutorials in these forums for removing this so I'd look up those before starting. (Search spark plugs removal) while up there be sure to unplug the upper oxygen sensor.





Next I put it up on jack stands to get up so I could "comfortably" work underneath it and removed the passenger side tire and the oil filter covers. This gave me a total of 3 access points to work reach the areas needed. While in the wheel well I removed the heat shield blocking the back side of the rear cat. There are 2 small bolts I believe size 10mm, one toward the inside of the engine and one easily accessed on the outside toward the wheel well.



After getting the MO off the ground I needed to drop the exhaust so I could access the cat mounting bolts that attach to the manifold. There are 3 bolts on each front and rear cat flange and 2 nuts in between on the central support bracket. There is a single bolt holding a bracket on the cat which can be seen in this picture. Also another support bracket just behind the engine on the bottom of the cross member. Lastly, dont forget the ground wire right in the middle of the vehicle. Once you remove these you need to support it. I used a couple spare pieces of wood to do this.





Now you are ready to tackle the lovely job of removing the 2 bolts and 2 nuts on the cat/manifold flange. The bolts come up from the bottom and the nuts are screwed onto 2 studs secured into the cat flange from the top. To access the nuts you will have to remove the manifold heat shield first. This is done by removing 3 10mm bolts that secure it. This part is one of the biggest pains because i had to crawl on top of the engine and reach around the back to access the 2 top heat shield bolts. This is also a good time to unplug the lower oxygen sensor.

To remove the 2 cat/manifold flange bolts you will need a 1/2" ratchet with a 6" and 10" extension (together) with a 14mm socket in order to reach the 2 bolts from the bottom. There is just barely enough room to get up from the bottom to access these. You will also most likely need the propane torch to heat these to loosen them. I first tried soaking them in penetrating fluid with no release. The heat works very well. I came in through the wheel well with a 14mm box end wrench in order to remove the 2 nuts. This is the biggest pain of the whole job, mostly because of the lack of space. Once you get these off you can drop the cat down through the frame and out the bottom of the vehicle.




With the cat out of the way you can finally access the manifold's 6 nuts. Nissan built these right and I had no trouble removing these nuts since there was no corrosion at all. After removing the 6 nuts using a deep well socket from the star studs coming out of the block I had son trouble maneuvering the manifold out of the way. There is an extension piece on the manifold flange that has another threaded hole apparently used by another application of the 3.5L manifold. I believe the maximal used this putter flange hole. I could have removed the studs if I had some torx wrenches but I didn't so I decided to take my cutoff tool and chop this extension off. You may or may not have this issue, and for some reason I was able to get the new manifold in with this extra tab on the flange. Unsure of why this is. Perhaps I just didn't wife it enough to get it out. You can see in the pic where I started cutting.





After I cut off the tab, I was able to remove the broken manifold and re-install the new one. Just follow these directions in reverse.



I'm not sure if this will help anyone, but I have been helped so much by this forum that I wanted to be able to do what I could. Since this is my first post EVER, please don't criticize too much. Best of luck!
 

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That's a dandy! But....I hope I never need it!
 

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I lucked out and got my mechanic to do this for 180 cash. Bought the manifold from amazon for 130. Had to replace the oxygen sensor myself since my mechanic mangled mine. So another 80. Little better than 400 all in. Nissan dealer quoted me 400 for the manifold, 600 labour and a possible extra 1000 to replace the cat.


Nice post thanks for the info :) coulda used this a month ago.
 

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Thanks for the post. It looks like I'm going to be doing this in 5 to 7 days (shipping time), I just purchased a Dorman rear exhaust manifold with all the goodies for $124. I have a Nissan service manual for my Murano and it makes it look so easy to do until you crawl under and see how much room you don't have to work with. Plus it never states about taking off the intake, every thing is done from the bottom. Which there isn't enough room for me to get in there, so I decided I was going to look for a mechanic to do the work. But after reading this post, I think I am going to give it a try. Removing the intake is the way to go, don't know why that isn't in the manual. Oh by the way, our local Nissan dealer quoted me $1400 to do it. Again thanks for the post.

Damon
 

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it is unnecessary to remove the UIM. everything is accessible from underneath. the only thing you need to do up top is disconnect the bank1 sensor1 o2 and unclip it from its retainer. i thought it was going to be a pain as well. but it really isn't all that bad. these cars aren't all that old. most of the fasteners should break loose. my advice; spray all fasteners with lubricant the night before. or as early as you can without driving the vehicle. also, for the 2 nuts holding the cat to manifold, double up on the wrenches to give leverage and break them free. use extensions approx. 2' long to get at the manifold nuts. because of the torque reduction caused by the extensions, you'll need to use a cheater bar for those probably. you'll get it. mine was pretty rusty under there. more rusty than you'd expect for an 04 vehicle. and i had no issues. just don't strip anything. if the 14mm socket feels a bit sloppy on there because of rust/corrosion, try a 13mm (example). if it's a bit snug, tap the socket on with a hammer. the tapping will shock the fastener and give a better chance of it breaking loose. use anti-seize on all the fasteners that you reinstall. and check that the big plug on the dorman manifold is tight before installing
 

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Finished my project today... :) . Changed spark plugs, valve cover gaskets, and rear exhaust manifold. I think I saved over $2200, compared to what the dealer quoted me. Just took it for an test drive, and everything was great, better acceleration and no exhaust leak noise..... :) . Thanks for the post, it all worked out great. Kaya, your right everything is accessible from the bottom. Once you remove the heat shields everything opens up and easy to get to. drgb, great post it gave me the push to do it myself, very detailed and great pictures. Also by removing the intake manifold you get to replace your spark plugs and valve cover gaskets. The other cool thing is................... I got to buy more tools required for the job and didn't have to justify it to the Misses........ :). Again great posts.


Thanks
Damon Chango
 

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feels good getting the job done on your own eh!
and keeping a good bit of money in the pocket helps too! haha
 

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My niece has a 04 MO with this problem. I threw a patch on it today so she could make it to payday, but I'm ordering the part tonight. While I was under there and looking at how I was going to get the manifold out I was thinking a lot what you guys were - what a pita this is going to be.
Being car forum savvy sure helps when you need info!
I'm a Subaru mech, but I work on a lot of different stuff. Just did a headgasket on a 2000 Isuzu NPR diesel. Not difficult, just messy and the cast iron head weighs close to 150lbs.
So this should be easy peasy, barring broken studs etc.
Thanks for making this thread OP!
 

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A big thanks to OP

First - DRGB - thanks for taking the time to create this thread, would not have done this without your pictures and notes. The picture you have of the cracked manifold is eerily similar to mine - cracked in the exact same place, virtually same crack pattern.

I was able to do this 100% from underneath, did not take the intake off or anything under the hood. 2007 Murano AWD.

Some notes from my experience to help anyone else out:

The heat shield that mounts to the manifold with the three 10mm bolts was one of the biggest bears to deal with. To a lesser extent putting them back on the new one was also a bit of a hassle.

I wound up having to basically tear the heat shield apart to get the old one off. There is only one lower bolt, and two uppers. I used a long pry bar to tear through the heat shield metal where the lower bolt goes through so I could then rock the shield back and forth to eventually crack the upper ones through as well. They were so rusted and seized, and with no access to them without taking the intake manifold off, there was not other option. Took a good hour plus just to get through that, but it did work. The new manifold comes with a new shield, so there was no loss in sacrificing the old one.

Putting the new shield on is a PITA as well, as there really is no room to get your hand up in there from below to access the upper bolts. As it turns out, I discovered it is possible to do, just lots of patience. I was able to get a 1/4" ratchet up in there to turn the two upper bolts a 1/16th of a turn each click, and even put antiseeze on them just in case down the road. Another tip - put the O2 sensor in temporarily while you get the upper bolts started, just so that one of the bolts doesn't slip out of your fingers in to the O2 hole and wind up stuck in the cat - which then requires you to start over, taking the CAT out to get the bolt out, etc. Don't ask me how I learned this tip. ;)

Disconnecting and reconnecting O2 sensor plug is a little bit of fun as well without removal of the intake, but with patience it is possible. Removal is pretty straightforward, re-installing a bit of fun. If you need reference for how the clip/release works, just look at the one on the front cat - they are exactly the same, and I found figuring out how to engage/disengage the release & lock was much easier with practice on the front one which is much more accessible.

Biggest and most valuable tip and is mentioned by others earlier in this thread - TORCH. Not optional. At least not for me. PB Blaster, etc. was of absolutely no use what so ever. I used a MAPP torch which will work with patience. If you have access to an oxy/acetylene setup, it would make it much quicker and easier. I had to get the bolts that connect the flex to the converter glowing red before they would budge. And I swear they were 13.5mm, since 14mm was way too loose, and 13mm I could not even air hammer on. I think the metal used is just of poor quality and the oxidation and rusting has made the head shrink slightly from the 14mm original size.

The converter to manifold bolts on the other hand are made of some serious metal, and didn't appear oxidized much at all. Make no mistake though, they are likely siezed also. In this case, it requires a lot of torch time with a MAPP setup, and it's pretty tight up there and you need to make sure the heat isn't melting near by seals, tubes/wires, etc. There is a lot of metal mass between the manifold and cat flanges at this joint, and the whole thing has to be glowing red before they will budge with 150K of heating/cooling/oxidation. A bigger wrench or more air for the impact really isn't the key here, it will just lead to stripping the head or cracking the bolt. Get 'em hot enough, and they will spin right out.

If you haven't changed your spark plugs, etc. and the manifold is due to come off anyway - I'd encourage you to do so. I had replaced the plugs within the last 10K miles and had no reason to take the manifold apart again so soon, which is why I spent a little more time fighting with the shield and O2 sensor plug to avoid this. Otherwise, it's really of no advantage to do so.

In replacing the exhaust from the resonator back through the muffler/tips, I found it peculiar that the exhaust is not support from the factory (at least no on my Mo) from the downstream cat all the way to the pipe above the rear control arm. This makes no sense - 7-8' of exhast just floating underneath, stressing those two hangers quite a bit. I'm pretty sure its all OEM, and no sign of something missing like it fell off at some point, etc. I added a hanger mid way just to strengthen things a bit.

All in all, it took me a solid day to replace the manifold, cat, as well as the exhaust from the resonator through to the rear muffler/tips assembly. Not a fun job at all to be honest, but not technically challenging either, just frustrating getting the old parts to break loose.

Anyway, to anyone else who takes on the challenge - Good luck!
 

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I do almost all my own repairs, but my time is valuable to me and I was concerned about seized bolts breaking off necessitating a trip to a professional shop anyway.

I was able to get this done for $850.00 at a shop I trust who used all Nissan OEM parts. He charged 8 hours labor as part of that fee.

Everyone's comfort zone is different but I wasn't tackling this myself. While he worked on that car I was free to work overtime at my job or work on one of my other car projects which weren't so menacing.

Just food for thought.
 

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There is a youtube on removing the rear bank1 cat "the easy way". It worked for me but the two nuts on top of the cat snapped 1 box end wrench but also broke loose at the same time. I didn't need to remove my exhaust manifold. Removed the passenger side tire and raised it up enough to get to everything. I always spay the nut and bolts with good penetrating lube and let it soak for a day. Then crank it just long enough to heat the exhaust. It can be a frustrating endeavor. If you haven't worked on exhausts, and don't have the proper tools, checking around at muffler shops is not a bad idea.
It can be done if you're good with wrenches. Nice pictures. Good thread.
 
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