exhaust manifold – The Jeep Guru

Exhaust Manifold Replacement Jeep Cherokee

After removing the old manifold and finding it too broken to repair, I ordered another one form my parts supplier Crown Automotive. I get great service from Crown and they supply quality parts. Their parts are near duplicates of the original Jeep parts and I can order with the Jeep part number.

I received my boxes early in the morning. However, one of the boxes was crushed. The box with the gasket was damaged as were the main manifold gasket and the air filter I had ordered. The doughnut gasket was fine as were some of the other parts in the box. I returned the damaged parts.

I compared the manifold to the original just to make sure it looked the same. It seemed well made but with some kinda sloppy welds. Just like the original.

I began by installing the EGR pipe in the new manifold. I had to heat the old manifold to get the EGR pipe out and the fitting at the end still did not want to swivel. I screwed it in the manifold and lined it up with where it would need to point to attach to the intake.

I cleaned off the head using a Scotch Brite wheel mounted in my drill. Luckily I had a spare gasket so I installed that. I then mounted the new manifold. It is way easier to get to the mounting bolts with the intake out of the way.

I then cleaned up the manifold mounting surface and sat it in place. Since it is very hard to get the bottom manifold bolts started, I tried setting them in place and loose hoping I could slip the manifold in behind the thick washers. I forgot about the dowels that the manifold has to slip over. So, I had to pull the manifold back out and pull the bolts.

Once the manifold was seated into place, I began the tedious task of getting all the bolts lined up and started into their threaded holes. The ones on the bottom were very hard for me. Once I finally got them all in I remembered to finish hooking up the EGR line. I had slipped the tube into the hole as I set the manifold in place but not started the nut.

I tried every possible angle and I could not get the nut to start. It would go in a thread or so and then pop back out. I tried from above and below. The tube looked aligned but it was obviously just a hair off. And with it seized in the exhaust I could not move it much to try to align it.

After struggling for an hour or so, I gave up and pulled both manifold back out. I found I could easily thread the pipe in with the manifold laying on the floor. I hoped that if the exhaust end freed up that I could attach it in place in the truck. So, I heated the nut cherry read and sprayed AFT on it until I could spin it around on the tube. I bolted the exhaust back in place and tried again. I tried it with the nut started in the intake but then it would not thread in the exhaust. I tried it with the nut started I the exhaust and it would not start in the intake. I wiggled the intake around every way I could but I could never get the nut to start.

So I took both manifolds off again. While I had the exhaust out this time I decided to remove the air warming tube because I don’t use it and it is really in the way for getting to the bottom bolts. I laid the manifolds on the floor and hooked up both tubes. I tightened the nuts almost snug but where the tube would still move a bit.

I then set the entire assembly in place as a unit just like I had taken it out. Putting the back nut on the exhaust mounting stud was a real struggle that involved some yelling and throwing wrenches before I finally worked my hand into the correct position. Eventually I was able to get all the bolts started into their threaded holes. I snugged up the EGR tube nuts and hooked up the down pipe to the new manifold.

I was tired and sore by that time so I called it a night and I will finish tightening the bolts later. Then I will have to hook back up all the vacuum and electrical connectors.
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Broken Exhaust Manifold Jeep 4.0

I have been hearing an exhaust leak in my off road Jeep Cherokee for a couple of years. Knowing that the 4.0 manifold is likely to crack, I did not think much about it. However, the noise has been getting worse and I am starting to see some indication that the leak was causing some cooling problems under the hood.

So, I decided to take a look to see how bad the crack was. I began by using a mirror and a flashlight. I pulled the air box to get more room. I was able to look over the front four runners pretty well and found no visible cracks. I know that the later HO manifolds tend to crack where the two section join. But this is the older style manifold that has one main tube and the runners are welded to it. No matter how I twisted the mirror, I could not see the back two runners.

So I decided to pull the intake and take a look. In some ways the old Renix manifold is easier to remove and in some ways it is not. One of the things that makes it easier is that the whole injector wiring harness can simply be unbolted at the firewall and stay with the manifold. There is no need to disconnect the individual injectors.

I did have to disconnect the three sensors below the engine. The O2 sensor, the block temperature sensor and the knock sensor all had to be disconnected to let the wiring harness stay with the manifold.

I had to remove the power steering pump from the bracket to access the bolt that holds the bracket to the manifold. Then I removed the fuel and vacuum lines. I was not able to get the EGR line to break loose so I had to remove the intake and exhaust manifolds as a unit.

Once I had them out and on the shop floor, I was able to get the EGR line to break free from the intake. I immediately saw severe cracking on the last runner near the O2 sensor bung.

I flipped the manifold over and saw cracking around the number five runner as well. I pulled on the pipe sand the last two runners separated completely from the manifold.

I had planned to re-weld the cracks but after seeing how broken up the pipes were and how brittle the surrounding metal was, I decided to order a replacement. I looked into getting a header but there are few to choose from for the older engine. I also thought about retrofitting the HO manifold but that would have meant redoing the down pipe back to the catalytic converter. I decided to simply replace it with a stock type manifold from Crown.