Jeep Wrangler JK: How to Repair Cracked Manifold
The exhaust manifolds on your Jeep are known to crack. You can replace them or try the following for a quick fix.
This article applies to the Jeep Wrangler JK (2007-Present).
The exhaust manifolds on your Jeep are in a pretty hostile environment. They get extremely hot, then water splashes on them and they instantly cool down. When you consider there is a lot of weight from the exhaust that hangs from them, it is no wonder they crack. Usually I don't recommend quick fixes, but this one is an easy and lasting one. It is easy to do yourself as long as you are committed to getting in there and getting it done. Once you get the heat shields off, it is actually really easy. Plus, the best part is it's really cheap and you may experience a better performing engine! You may have to replace the manifold later, but to get it fixed now, this is a great way to do it.
Materials Needed
- Penetrating fluid spray
- 3/8" drive ratchet and long extension
- U-joint for 3/8" ratchet
- 10mm socket
- Wire brush
- Brake cleaner spray
- Quiksteel or Thermosteel
Since you must remove two manifold bolts plus one nut, caution is required. If you break any of these, a simple repair will turn into a major one.
Step 1 – Remove heat shield
The heat shields cover the crack, so they must go. Remove the two bolts that hold the upper shield in place with a 10mm socket and a very long extension with a U-joint. The lower shield is held on by a 10mm nut. Soak it with penetrating fluid and allow to set before trying to crack it loose.
Figure 1. Exhaust heat shields. 
Figure 2. Removing bolt with extension and U-joint. 
Figure 3. Lower heat shield nut.
Pro Tip
Allow the penetrating fluid to soak in as long as possible to do its job.
Step 2 – Clean cracked area
It is very important to clean really well the area where the crack is. A wire brush will get the loose stuff off. Consider spraying down the whole area with brake cleaner.
Figure 4. Cracked manifold. 
Figure 5. Manifold cleaned with wire brush.
Pro Tip
The better the prep, the better the repair.
Step 3 – Apply sealer
Both Quiksteel and Thermosteel are Blue Magic products that fellow Jeep enthusiast recommend. Follow the directions when applying. The first thing to do is mix the sealer really well. If you don't, it will not set up and make a mess you don't want to deal with. Then apply it to the cracked area as thick as possible. You can use your finger or a flat blade screwdriver. Work it in to the crack, so it really gets in there and seals it.
Figure 6. Thermosteel sealer. 
Figure 7. Quicksteel sealer.
Once applied, it has to cure for at least several hours. Overnight is better. Start your Jeep and let it run for a few minutes, then stop. Do this several times so the sealer gradually gets heated up more and more. You will be able to smell it for several days until it really gets cured.
Pro Tip
Waiting overnight is the best, as is the slow heating up after done. Your patience will be rewarded!
Step 4 – Reinstall heat shields
Reinstall the heat shields. Start with the bottom one held on with the nut. Just snug it up. Then put the two bolts back in the head, being very careful to get them started without being cross-threaded. Torque them to 22 ft/lbs. Now you are done and not only will your Jeep be quiet, but the oxygen sensor will not pick up what it thinks is a lean condition. Enjoy!
Pro Tip
Since you are there, apply anti-seize compound to the bolts and nut so they come out easy next time.
Related Discussions
- Has Your Exhaust Manifold Cracked - JK-Forum.com
- Is Cracked Manifold Covered Under Warranty - JK-Forum.com
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- Fix Manifold Cracks with Thermosteel - JK-Forum.com
