This is my first rodeo with a TJ with a 4.0. I'm sure I'm not the first to run into this. Probably not the last. Just trying to share the knowledge. Pictures included as I can.
The story starts with a cracked exhaust manifold. A well known problem and one that came with the 1999 TJ I bought a few months ago. I sourced a new and improved one with the flex pipes to prevent future cracks. I finally got around to replacing it recently. First problem, the manifold bolts were rusted to the point I was surprised they came out at all. So, had to get a bolt kit. Yesterday they came in and I went to put it together. After struggling to get proper torque on the bolts, I thought I had it ready to go. It was past dark by the time I got to fire it up. After few seconds cranking, it fired up, and immediately went to the rev limiter, 5K+! I shut it down and checked everything. Couldn't figure out why so I tried it again. Same thing happened. I tried to see what it was doing and then saw the exhaust glowing so I shut it down again. After doing some research, I came up with a couple possibilities. Vacuum leak and improperly installed intake. I ruled out the vacuum leak as I had recently smoke checked everything and already replaced worn out boots. Today I was able to look at the intake manifold better and found the lower side to have a gap. When I got everything apart again, I found out why. I had not gotten the intake on the alignment dowels/pins correctly. What was worse, I had cracked the manifold in a couple places.
In conclusion, make sure to get the manifold attached properly before torqueing down. Or you will be waiting on parts, again.
Cheers
The story starts with a cracked exhaust manifold. A well known problem and one that came with the 1999 TJ I bought a few months ago. I sourced a new and improved one with the flex pipes to prevent future cracks. I finally got around to replacing it recently. First problem, the manifold bolts were rusted to the point I was surprised they came out at all. So, had to get a bolt kit. Yesterday they came in and I went to put it together. After struggling to get proper torque on the bolts, I thought I had it ready to go. It was past dark by the time I got to fire it up. After few seconds cranking, it fired up, and immediately went to the rev limiter, 5K+! I shut it down and checked everything. Couldn't figure out why so I tried it again. Same thing happened. I tried to see what it was doing and then saw the exhaust glowing so I shut it down again. After doing some research, I came up with a couple possibilities. Vacuum leak and improperly installed intake. I ruled out the vacuum leak as I had recently smoke checked everything and already replaced worn out boots. Today I was able to look at the intake manifold better and found the lower side to have a gap. When I got everything apart again, I found out why. I had not gotten the intake on the alignment dowels/pins correctly. What was worse, I had cracked the manifold in a couple places.
In conclusion, make sure to get the manifold attached properly before torqueing down. Or you will be waiting on parts, again.
Cheers
