Exhaust Manifold Problem, Please help!

I recently purchased a 2001 Jeep Cherokee that my son found and had to have. I knew it had an exhaust leak that I thought I could fix or get fixed fairly easily. However, after searching deeper into the problem, I found that the engine had been replaced with and older model, I believe to be around 91-95 based on the casting numbers of 53008405. The 2001 Jeep Cherokee has a two piece manifold with two C02 sensors. Two more C02 sensors located in the two cat converters, just below the manifolds. 91-99 4.0L engines had a one piece manifold with no C02 sensors. With that foundation laid, I have a 2 part question. Obviously, the 2001 two piece manifold will not fit the 95 engine because exhaust leaks from the bottom side of the manifold. It doesn't completely cover the exhaust port. If I install the 95 exhaust manifold, and cut out the two cat converters, what do I do about the 4 C02 sensors? Anyone else run across this problem before? Thanks in advance for any help you can give.

Before you go too far down that road, removal of catalytic converters is a federal offense. does not condone this practice.

I agree, I'm just looking for suggestions!

If it is indeed an older motor, you should be able to delete the two downstream 02 sensors, I think.

I wondered about that as well. I also thought about cutting the wiring harness from the two sensors that I would loose, and splice those onto the two senors that I would keep. One sensor two plugs. The computer would be receiving information from what it would perceive as 4 sensors and not just two.

I am a heating and cooling contractor, not a mechanic. Therefore, I am open to suggestions from those who know better. Here is one of my own solutions that I would like some feedback on...I purchased the manifold gasket for the 1995 4.0L engine, and the gasket for the 2001 exhaust manifold. I plan to have a 12ga. plate cut to the pattern of the 2001 exhaust gasket. Sandwich this plate between the two gaskets. That would taper the port opening down to the 2001 exhaust manifold size, and allow me to keep all the cat converters and C02 sensors in place. Changing the head to a later model would also fix the problem, but the older head has slightly larger valves, which translates into little better performance. I would rather keep that older head if that is possible.

If I do the plate thing, am I missing something that could cause problems later?

The big thing that will stop you is the fact that 00 & 01 went to the distributorless ignition which means it MUST have the 00+ head on an older block. The 00+ had a 2 pkece manifold with the two sensors then two cats with another two sensors like you are seeing. You have the correct head and exhaust so the leak is due to something else. Furthermore you cannot splice the sensors together as each one is programmed to see a different reading.

Sounds like a franken-car. My guess is you have an old-style head, and the coil rail is either sitting on adapters or just hanging free, sitting on top of the plugs.

It should be bolted down to bosses cast into the head. If it's not, you have the old style head, and this explains your exhaust leak.

You can't easily do away with the 4 O2 sensors, the late OBD-II system needs them.
You might be able to buy a late-model header(Banks makes the only one I'm aware of)and modify the port shape to match the earlier head. Expensive, but probably cheaper then replacing the head. Another option would be finding a used'01-up head('01 XJ, '01-'06 TJ) and do the head swap.

dave92cherokee said:

The big thing that will stop you is the fact that 00 & 01 went to the distributor-less ignition which means it MUST have the 00+ head on an older block. The 00+ had a 2 piece manifold with the two sensors then two cats with another two sensors like you are seeing. You have the correct head and exhaust so the leak is due to something else. Furthermore you cannot splice the sensors together as each one is programmed to see a different reading.

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What you are stating about the 2000+ year models is very well correct. However, this engine does have the older model head, because the exhaust ports on the head are much larger than the 2001 (2 piece) exhaust manifold that is bolted to it. I can reach under and stick a pocket knife blade between the port and manifold. So I am quite sure where the exhaust leak is, 6 of them to be exact. Also, the mechanic that installed this engine, has set it up as a distributor-less engine. That is why I was fooled in believing that it was the original. The casting numbers on the block and head however, tell a very different story. With the exception of the exhaust leak, this engine runs very well. Thank you for your comments, and views on this issue. All of these posts are read and appreciated.

tbburg said:

Sounds like a franken-car. My guess is you have an old-style head, and the coil rail is either sitting on adapters or just hanging free, sitting on top of the plugs.

It should be bolted down to bosses cast into the head. If it's not, you have the old style head, and this explains your exhaust leak.

You can't easily do away with the 4 O2 sensors, the late OBD-II system needs them.
You might be able to buy a late-model header(Banks makes the only one I'm aware of)and modify the port shape to match the earlier head. Expensive, but probably cheaper then replacing the head. Another option would be finding a used'01-up head('01 XJ, '01-'06 TJ) and do the head swap.

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YES! YOU ARE CORRECT! The coil rail is wired on with bailing wire from valve cover bolts on top to some other bolts underneath. I had it in my head that I needed to put some bolts in those holes, and take off that wire......Until I read your post, I never thought about studs being casted into the later model heads. Changing the head to a later model, just may be the best solution! At least that puts things back to a more original state. Thank you for this post!

You can definately see how much material was removed from the 91-99 manifold when they went to the 2 piece setup. Is it possible to just get one of the earlier manifolds then drill a hole and weld in a couple of O2 sensor bungs?

You cound probably mod a single piece manifold, adding an O2 sensor bung on each side of the "Y" connection, thereby giving you a front and rear O2 read. You can get O2 bungs from exhaust shops, or on line from places like Summit or Jegs. I'm not sure how well it would work putting the 2 downstream sensors behind the single cat. It might work.

As for the coil rail, search in mod tec. there are a lot of people who have converted the late model motors to run the earlier head, and have made conversion brackets to hold the rail in place. Search for "0331" or "cracked head". A lot of the '00 models had head problems that destroyed the motor, also probably why your motor was swapped.

You may want to PM a moderator to move this thread into mod tec. The MJ forum is for the trucks, and they quite making the trucks long before they installed the coil rail. You'll get a lot bigger response in mod tec.

tbburg said:

You cound probably mod a single piece manifold, adding an O2 sensor bung on each side of the "Y" connection, thereby giving you a front and rear O2 read. You can get O2 bungs from exhaust shops, or on line from places like Summit or Jegs. I'm not sure how well it would work putting the 2 downstream sensors behind the single cat. It might work.

As for the coil rail, search in mod tec. there are a lot of people who have converted the late model motors to run the earlier head, and have made conversion brackets to hold the rail in place. Search for "0331" or "cracked head". A lot of the '00 models had head problems that destroyed the motor, also probably why your motor was swapped.

You may want to PM a moderator to move this thread into mod tec. The MJ forum is for the trucks, and they quite making the trucks long before they installed the coil rail. You'll get a lot bigger response in mod tec.

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I agree with this method. Putting two together before the cat, and two together after the cat should work. You may just need to extend the 02 sensor wiring to reach where needed.

dave92cherokee said:

You can definitely see how much material was removed from the 91-99 manifold when they went to the 2 piece setup. Is it possible to just get one of the earlier manifolds then drill a hole and weld in a couple of O2 sensor bungs?

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Yes, that is possible! What I would do is drill the hole, then weld a grade 8 nut over the hole so that the c02 sensor could be replaced if needed later. That does solve that problem, but as you can see by your images, the single manifold attaches to one exhaust pipe. I have two cat converters that has to attach to that single manifold, and I'm not sure how to make that happen. I guess I could get the older manifold and let the muffler shop figure that part out. He could make a "Y" piece to attach the cat converters. I will ponder on that idea as I stop by the muffler shop and ask Steve if he can make it for me. Thanks for that idea, it may get the car going again sooner than looking for a late model head. So far I have had no luck locating one. The scrape yards are not willing to part with the head from a good running engine.

dasbulliwagen said:

I agree with this method. Putting two together before the cat, and two together after the cat should work. You may just need to extend the 02 sensor wiring to reach where needed.

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Thank you for the comments. I also recently realized that I started this thread in the wrong area of this forum. I wasn't sure how to move it, or if I should start it again in another location. However, the feedback that I have been getting here from the "MJ" owners has been very positive, and everyone seems to be truly concerned about my problem. The responses have all been great ideas, and has caused me to stop and think out the possibilities of each one of them. So far I can't recall reading anything that is beyond the possibilities of a legitimate solution to this problem. Some solutions costs more than others, but they all have there validity.