Hey all,

I've got the patent cherokee "whistling/gurgling under load with mild loss of power" symptoms that point screaming flashing lights at a cracked exhaust manifold as these flying boxes are wont to do, but! I noticed something while under her scoping it out that gave me pause: The front pipe appears dented. I can't find any reference photos, so I wanted to run this one by you before I take her to the muffler shop (CA Emi$$ions means I'm not going to risk scungling this one up home-gaming it, I'm getting her done all professional like.) Here's what it looks like:







So, here's the questions, given my cursory from-the-bottom inspections of the manifold didn't reveal any visible cracks or breaches:

1) Is this stock and the pipe is just oddly shaped from the OEM, or has something come along and dented my front pipe?

2) If this is indeed damage, does it seem severe enough to be causing the cracked manifold symptoms I'm getting above?

Much love and thanks for the advice, hopefully I can save some cash going into the shop with my big boy pants on.

 

Annnd answered my own question with these threads: It's the factory dimple for the 4X4 driveshaft, which my RWD doesn't have. Mystery solved, cracked manifold it is.

https://www.cherokeeforum.com/f2/exh...pe-dent-32071/
https://www.cherokeeforum.com/f2/den...st-pipe-47202/

 

OR is it this:
"The "Dent" in the pipe just past the collector donut seal provides 1-2 psi backpressure. Jeep designed it this way to give the HO 4.0 a fatter torque curve, down low in the RPM range. it also helps gas mileage, and gives the motor a nice feel.
It is NOT a defect.
It is NOT for clearance.
It DOES looks like crap, and sloppy engineering, I agree.
Removing it will cause two things:
A slight bog in the lower RPM range.
A slight decrease in gas mileage.
The backpressure keeps a little more exhaust in the upper section of the header just past the exhaust valve which forces the motor to extract a little more heat (power) from the freshly burned fuel/air charge coming out of the cylinder.
If you check the factory .pdf file for the 93' and 2000', you will find a test for backpressure and how it is done by removing the first Oxygen sensor....specifically, "1-2 psi while running is correct"....and is necessary for proper motor functioning. It is also the best and quickest test for plugged cat converters.."

Either way the dent is OEM.

 

Very informative, thank you! Yeah that's very likely it, and the symptoms I'm having I don't think match a blocked cat or other exhaust blockage (and the cat was replaced recently due to failure and rattle.) All signs point to a cracked manifold, so I'll have the shop examine and likely replace with an ATP 101212.

 

My 99 2wd had that dent. Most will have that dent.