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Discussion Starter #1
Both exhaust manifolds on my 01 3.3l are cracked. The passenger side has been cracked for a long time, probably 7-8 years and 100k miles. It was never too bad and would close up when the engine warmed up. The drivers side broke about 3 years ago and the crack is big and noisy but I haven't driven the truck much for the past 2.5 years. Bottom line both are broke and need replaced.

Has anyone replaced the exhaust manifolds themselves? I plan to do this before winter. I'm looking at the dorman parts because they are cheap, but how is the quality? Also, can you access everything from the top or do it need to come from the bottom?
 

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I replaced the right one with a Dorman from Rock auto. Took about 2 hrs and make sure you use penetrating oil on the studs first.
 

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Dorman manifolds are good and they have a lifetime warranty. The passenger side is the easier of the two to replace. You can access the manifold nuts from the fenderwell. You'll probably have to get under the vehicle to disconnect it from the exhaust front pipe. A large prybar can be used to pull the exhaust toward the passenger side to get enough clearance to remove the manifold from the studs and then the manifold can be removed from the top side. The driver side is a bit tougher. Assuming you don't have the supercharged engine, you have to deal with the EGR passage pipe between the top of the manifold and the EGR valve. Be very careful as these pipes are discontinued and often the EGR valve will break inside the end of the pipe when trying to remove it. The pipe nut on the bottom also tends to rust to the pipe. If you want to remove the exhaust manifold from the top, you may be able to do it if you remove the intake plenum, but it's been so long since I've done a left side manifold that, honestly, I forgot how I did it!. Also, don't be surprised if the manifold shield bolts break or round off when trying to remove them, as that's pretty routine. Fortunately, Dorman gives you new shields.
 

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Depending on your mileage, I would replace both catalytic converters at the same time. To gain access to the manifolds to remove them is 95% of the same work to get to the cats. And it's a pain in the arse. I got all my parts from Rock Auto when I did mine. (02 Xterra)
 

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Depending on your mileage, I would replace both catalytic converters at the same time. To gain access to the manifolds to remove them is 95% of the same work to get to the cats. And it's a pain in the arse. I got all my parts from Rock Auto when I did mine. (02 Xterra)

185k and I thought about it. If they were 50 or so a piece I would just replace them. But I'm not really ready to drop $400 dollars just because it's convenient now.
 

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Discussion Starter #6
Dorman manifolds are good and they have a lifetime warranty. The passenger side is the easier of the two to replace. You can access the manifold nuts from the fenderwell. You'll probably have to get under the vehicle to disconnect it from the exhaust front pipe. A large prybar can be used to pull the exhaust toward the passenger side to get enough clearance to remove the manifold from the studs and then the manifold can be removed from the top side. The driver side is a bit tougher. Assuming you don't have the supercharged engine, you have to deal with the EGR passage pipe between the top of the manifold and the EGR valve. Be very careful as these pipes are discontinued and often the EGR valve will break inside the end of the pipe when trying to remove it. The pipe nut on the bottom also tends to rust to the pipe. If you want to remove the exhaust manifold from the top, you may be able to do it if you remove the intake plenum, but it's been so long since I've done a left side manifold that, honestly, I forgot how I did it!. Also, don't be surprised if the manifold shield bolts break or round off when trying to remove them, as that's pretty routine. Fortunately, Dorman gives you new shields.

Reviving this because in getting ready to start buying exhaust parts including manifolds.

I was under the hood today to spray PB Blaster on manifold stuff an I noticed that I don't have an EGR tube or valve. It seems there is just a big cap/plug over where the egr tube would go.

Have you (or anyone else) had to deal with any broken studs holding on the manifold? What recourse do you have? Are you usually able to turn the rest of the stud out or do you need to drill and retap the head? Where can I find studs?
I
 

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The 3.0L engines only had 8MM studs and they would break all the time. When they came out with the 3.3L, they went with 10MM studs which hardly broke, but instead the exhaust manifolds would crack! I won't say it never happens, but they "usually" don't break. New ones can be ordered from Nissan; there are a couple of different length studs used. As far as removal of a broken stud, it all depends if it breaks flush with the head or if there is enough of the stud remaining to get an extractor on it or even weld a bolt to it to help remove it. If it breaks flush, then it will have to be drilled out. Hopefully, you won't encounter that problem!
The supercharged engines didn't have the EGR passage pipe; it was only the non-SC engines that had them. I'm not sure which one you have. If you have a non-SC engine, then somebody probably deleted the EGR valve and passage pipe and plugged them off.
 

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Discussion Starter #8
I am 2001 (built late 00) Non-Supercharged. Ive had the truck since 70k miles. I'm surprised someone deleted the egr before then. Was that a common thing to do or were the valves known to go bad early? What would the benefit be of deleting it?

So there were different length studs in the six locations that hold the manifold on?
 

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Here's a link to the part diagram of a 2001 Frontier VG33E EGR system so you can see for yourself:

https://www.nissanpartsdeal.com/par...ier/egr-parts.html?Filter=(1=KC;2=VG33E;4=4WD)

I can't tell you what the reason was; some people think it improves performance, which it might do to an extent, but at the cost of potential accelerated wear to the pistons. The EGR system is used to reduce NOX emissions, but does so by helping to control pre-ignition by controlling combustion temperatures by adding inert gas to the mix. Another possibility is that they had to remove the plenum for some reason and the EGR valve broke inside the end of the passage pipe and they didn't want to deal with fixing it correctly.

As far as the exhaust studs, there are two different length studs. Refer to part codes 14004A and 14004AA in the part diagram linked below:

https://www.nissanpartsdeal.com/par...er=(1=KC;2=VG33E;4=4WD;5=XE)&Diagram=140_B002
 

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Discussion Starter #10
Thanks.

You're sure ALL vg33e frontiers had the EGR?

Manifolds will be here this weekend. I'm still thinking about just taking it to someone to do them.
 

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I just replaced the passenger side the other day and I'm about to put the drivers side one on today, I got the dorman manifolds from oreillys...

Was wondering which catalytic converters will fit with these? Rock auto sent me what was supposed to be a bosal but it came in a magnaflow box with all the warranty paperwork and hardware so I think they sent me a magnaflow... but it doesn't quite seem to fit with the heat shield mount on the dorman manifold, it will dent the outer heat shield/ shell of the 'magnaflow' so i think im going to send it back...
 

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I always go with Walker when it comes to catalytic converters.
 

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Do you have the dorman manifolds as well?
My manifolds are still factory originals, but the front converters are Walkers. The Dormans should be the same as the Nissan manifolds.
 

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I found this thread interesting on EGR valves on the 3.3L-V6. It looks like some VG33E engines around 2000-2001 did not have EGR valves, likely the Federal emissions vehicles, and some did, likely California emissions vehicles. It also seems to suggest that they all had EGR valves later on. The ECM's also seem to be specific to EGR vs. non-EGR models. The supercharged, VG33ER engines, don't have EGR's:

Is EGR present on all engines, or just some? [Archive] - Nissan Xterra Forum
 

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Discussion Starter #17
I did some googling when I first saw I didn't have an EGR valve and saw a little bit of info about early trucks not having it from the factory. I figured that had to be the case because I don't have any codes related to it and never have. Deleting the EGR would throw a code if something tricky wasn't done to make the system think it was working normally. I didn't find anything that said there was an easy solution to this.

I also think my intake plenum is different because I dont believe there is even a place to bolt the EGR valve.

Back to exhaust manifolds, I took the heat shields off of them today so I could better access the studs with Blaster. The studs don't look all that rusted so I'm hoping I'll be ok there. The studs on the cats are another story but that's an easier fix than busting one off in the head. I'm becoming increasingly worried that I'll end up replacing both upper cats and the o2 sensors. I wasn't really looking to spend THAT much on this truck. We will see how well it all comes apart.

Mfoley, you said you dropped the front driveline to get the drivers side out/in. I really don't want to do that, what are they alternatives? Remove the plenum to get them out the top? Can I just remove the front drive shaft and have enough room to pull the cat and then the manifold out the bottom?

Something Else that has me worried... With my heat shields off it's very obvious my passenger side is cracked. I didn't do an extremely detailed inspection but I didn't see any cracks on the drivers side and it is MUCH louder than the passenger. I need to look a little harder now to make sure I don't have some other problem. Any thoughts?
 

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I might have worded it wrong but I just unbolted the drive shaft going into the transfer case, 4 bolts with nuts on them pulled back the yolk and let it hang down. this allowed me to drop both cats out the bottom at the same time. mine were and still are rusted together on the drivers side.. I also didn't want to spend as much time and money basically rebuilding this thing.. I am having fun though I want to figure out what is causing mine to lose power. I might end up having to buy cats too, I mean at 215,000 they're probably worn out..

Oh yeah and my passenger side was cracked in like 3 spots, drivers side like basically all the way in half, but only at the bottom I didn't see it until I pulled it out.
 

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For whatever reason, the passenger side or right bank manifolds on VG engines are always the most prone to cracking, whether it's a Frontier, old Maxima or Quest. On the 3.0L's on the earlier Hardbody/WD21 Pathfinders, the were always the most prone sides for exhaust stud breakage.
 

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Discussion Starter #20
I might have worded it wrong but I just unbolted the drive shaft going into the transfer case, 4 bolts with nuts on them pulled back the yolk and let it hang down. this allowed me to drop both cats out the bottom at the same time. mine were and still are rusted together on the drivers side.. I also didn't want to spend as much time and money basically rebuilding this thing.. I am having fun though I want to figure out what is causing mine to lose power. I might end up having to buy cats too, I mean at 215,000 they're probably worn out..

Oh yeah and my passenger side was cracked in like 3 spots, drivers side like basically all the way in half, but only at the bottom I didn't see it until I pulled it out.

So on the drivers side you were able to unbolt the cat from the manifold and pull both cats out the bottom still connected to each other with just the front driveshaft off.

My passenger side looks like you describe and I'm assuming the drivers side will also. I see nothing on top of it but it's very obviously leaking somewhere. It's hard to get eyes on the bottom of it, I can barely see all the nuts!
 
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