Novak Conversions Jeep Wrangler TJ radiator

Question on the factory exhaust system of an '04

CJP04

Member
Original poster
Joined
Mar 25, 2018
Messages
41
Location
Philadelphia, PA, USA
I plan on replacing the entire exhaust system on my '04 with the 4.0, but I'm rather confused as to its setup.

I notice on my TJ that the exhaust manifold splits into 2 pipes that converge directly in front of the oil pan, and then head to the catalytic converter. However, with all the exhaust systems I see available for purchase, just one pipe heads to the exhaust manifold. Can someone please explain this difference, please?

Also, if you can recommend (with a URL) a good OEM or after market exhaust for my TJ's particular exhaust setup, that's be great! Thanks in advance!

Here are some pictures of my TJ's exhaust setup:
 
I plan on replacing the entire exhaust system on my '04 with the 4.0, but I'm rather confused as to its setup.

I notice on my TJ that the exhaust manifold splits into 2 pipes that converge directly in front of the oil pan, and then head to the catalytic converter. However, with all the exhaust systems I see available for purchase, just one pipe heads to the exhaust manifold. Can someone please explain this difference, please?

Also, if you can recommend (with a URL) a good OEM or after market exhaust for my TJ's particular exhaust setup, that's be great! Thanks in advance!

Here are some pictures of my TJ's exhaust setup:

There were two different setups. Prior to 2000, there was a one piece exhaust manifold that went down to the exhaust, then there was one catalytic convertor before to the muffler.

Sometime in 2000 due to emissions, they switched to a system that looks like your current system, in which there is a smaller exhaust manifold, a "down pipe" of sorts (if you could call it that) that includes two pre-cats in it, then the exhaust system, one more cat, then the muffler.

You'll find around here that we don't recommend aftermarket exhaust "systems". This is because they are overpriced and a waste of money (big time). You can go to any good exhaust shop as most of us have, and they will build you a new exhaust system for much cheaper (seriously a lot cheaper).

The only exception to this would be if you need to replace your pre-cats, in which case I suggest purchasing the Walker ones, then having the rest of the exhaust system done by a reputable local exhaust shop.

The correct Walker system for your 2004 would be this one here:
https://www.amazon.com/dp/B001AGP864/?tag=wranglerorg-20

Bring that with you to an exhaust shop and tell them you want them to install that, plus a new exhaust system, and they'll do it for way cheaper than one of the pre-packaged solutions from Borla, Magnaflow, etc.
 
  • Like
Reactions: Nimbley and CJP04
There were two different setups. Prior to 2000, there was a one piece exhaust manifold that went down to the exhaust, then there was one catalytic convertor before to the muffler.

Sometime in 2000 due to emissions, they switched to a system that looks like your current system, in which there is a smaller exhaust manifold, a "down pipe" of sorts (if you could call it that) that includes two pre-cats in it, then the exhaust system, one more cat, then the muffler.

You'll find around here that we don't recommend aftermarket exhaust "systems". This is because they are overpriced and a waste of money (big time). You can go to any good exhaust shop as most of us have, and they will build you a new exhaust system for much cheaper (seriously a lot cheaper).

The only exception to this would be if you need to replace your pre-cats, in which case I suggest purchasing the Walker ones, then having the rest of the exhaust system done by a reputable local exhaust shop.

The correct Walker system for your 2004 would be this one here:
https://www.amazon.com/dp/B001AGP864/?tag=wranglerorg-20

Bring that with you to an exhaust shop and tell them you want them to install that, plus a new exhaust system, and they'll do it for way cheaper than one of the pre-packaged solutions from Borla, Magnaflow, etc.

I really appreciate that crash course to explain the difference between the 2 types of exhaust systems I'm seeing in the TJ.

With that in hand now, and your recommendations, I'll likely have a local Jeep mechanic perform a diagnostic on my Jeep's exhaust system to see where this rattling is coming from. If it's coming from the main catalytic convert or the muffler, then I'll just have him rebuild the exhaust system. If the rattling is coming from one or both of the pre-cats, then I'll purchase your recommendation and have him rebuild the rest.
 
  • Like
Reactions: Chris
I really appreciate that crash course to explain the difference between the 2 types of exhaust systems I'm seeing in the TJ.

With that in hand now, and your recommendations, I'll likely have a local Jeep mechanic perform a diagnostic on my Jeep's exhaust system to see where this rattling is coming from. If it's coming from the main catalytic convert or the muffler, then I'll just have him rebuild the exhaust system. If the rattling is coming from one or both of the pre-cats, then I'll purchase your recommendation and have him rebuild the rest.

Happy to help! Based on those photos of yours, it looks like your cats are in need of replacing soon anyways!
 
Happy to help! Based on those photos of yours, it looks like your cats are in need of replacing soon anyways!

Yeah, there's a few things under there that need to be replaced. ;)

I forgot to ask: do you recommend a specific catalytic converter, muffler, and exhaust? I assume the Walker brand?
 
Yeah, there's a few things under there that need to be replaced. ;)

I forgot to ask: do you recommend a specific catalytic converter, muffler, and exhaust? I assume the Walker brand?

Yeah, I replaced mine with the Walker brand. They work well and should last another 100k plus miles at least! As for the muffler, I run a Magnaflow. The piping is just whatever the exhaust shop used.
 
There were two different setups. Prior to 2000, there was a one piece exhaust manifold that went down to the exhaust, then there was one catalytic convertor before to the muffler.

Sometime in 2000 due to emissions, they switched to a system that looks like your current system, in which there is a smaller exhaust manifold, a "down pipe" of sorts (if you could call it that) that includes two pre-cats in it, then the exhaust system, one more cat, then the muffler.

You'll find around here that we don't recommend aftermarket exhaust "systems". This is because they are overpriced and a waste of money (big time). You can go to any good exhaust shop as most of us have, and they will build you a new exhaust system for much cheaper (seriously a lot cheaper).

The only exception to this would be if you need to replace your pre-cats, in which case I suggest purchasing the Walker ones, then having the rest of the exhaust system done by a reputable local exhaust shop.

The correct Walker system for your 2004 would be this one here:
https://www.amazon.com/dp/B001AGP864/?tag=wranglerorg-20

Bring that with you to an exhaust shop and tell them you want them to install that, plus a new exhaust system, and they'll do it for way cheaper than one of the pre-packaged solutions from Borla, Magnaflow, etc.
That “one more cat” is in the way of my ultra high clearance Ucf skid on my 01 TJ. Can it be deleted???!! So annoying. If I tighten the skid bolts all the way in it bends the exhaust up and hits tracker bar and forces up rear hanger. PITA!
 
That “one more cat” is in the way of my ultra high clearance Ucf skid on my 01 TJ. Can it be deleted???!! So annoying. If I tighten the skid bolts all the way in it bends the exhaust up and hits tracker bar and forces up rear hanger. PITA!

Yep, I deleted mine when I did the tummy tuck. Just be prepared, it's going to be a lot louder ;)
 
  • Like
Reactions: Rick Flair
Excellent is it super loud - wonder what I could do to quiet it if so? Maybe a resonator in place of it- small one?

It's not insanely loud, but it's definitely a lot louder than it is stock. You could probably have them put a small resonator in place of it I suspect. That's what I would do next time around.
 
Novak Conversions Jeep Wrangler TJ radiator