The exhaust manifold was cracked on our Jeep. This is quite common for the 4.0 inline 6 on the Jeeps. It looked as if it had been repaired numerous times before through some welding, but we found several hairline cracks at the spots where the pipes merged.

We replaced it with a solid exhaust manifold from Ebay and not the kind with the flexible couplings on it. One of our friends who used to be a Jeep mechanic said he repaired just as many manifolds with the flexible couplings than without. In fact, the flexible parts were known to break. I could have bought a higher performance exhaust manifold from SummitRacing.com, but I just bought a cheaper upgrade that looked like it would last. It was still quite an improvement over the stock manifold which is a 6-2-1 design (going from 6 pipes to 2 to 1 and then to the exhaust) to a 6-3-2-1. We coated the exhaust manifold with Duplicolor Engine Enamel & High Heat (DE 1613 Gloss Black), however to our suprise the paint actually started burning off the exhaust manifold when we started the engine.

We had followed the directions for the paint and the conditions outside when we painted it were considered okay according to the label. I guess we were unlucky, but I was deeply disappointed with the product. Luckily you cannot see the exhaust manifold very well in my Jeep since the intake manifold covers it almost completely.

The rest of the exhaust system was also damaged. The exiting pipe on the muffler had shaken loose on the inside of the muffler, it produced an unbearable shaking noise at idle. The catalytic converter was also broken, the inside honeycomb was loose. I had several options on how to replace it. There's a guy, Kolak, who sells exhaust systems for Jeeps. He has a really good reputation, but to be quite honest his estimates were outside of my budget. So I ended up going with a Dynomax Cat-back system (part #WLK-17403). Please note, as you can see in the product number, this is actually manufactured by a company called Walker. They sell the exact same system. The kit contained a new muffler and a new tailpipe. I covered most of the tailpipe with some of the left over Duplicolor engine enamel paint. Since the tailpipe does not get as hot as the exhaust manifold, I figured I wouldn\'t have the same issue as I did with the paint burning off on the exhaust manifold, and indeed it worked nicely. We replaced the original catalytic converter with a universal 2.25" Magnaflow carsound highflow cat. The new exhaust system is quite a bit louder, but still quiet compared to most aftermarket exhaust systems. It has a nice little rumble at idle and a bit more kick if you give more throttle.