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August 23, 2019, 04:47:02 PM

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Author Topic: '07 JK left side exhaust manifold replacement  (Read 38985 times)
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« on: June 10, 2011, 07:54:24 AM »

Recently I found that I had an exhaust leak in my engine compartment. When the engine was cold, I could hear and smell an exhaust leak. After the engine warmed up, it would seem to go away. After reading about other JK owners with cracked exhaust manifolds I looked into it…

Apparently, JK’s have a common tendency to develop cracks in the exhaust manifolds. Primarily on the drivers side (left side). According to what I have read, some manifolds have developed cracks after as little as 10k! Clearly this would be covered under warranty. Unfortunately my JK is well out of warranty and the manifold is not covered under the Federal Emissions Warranty according to Manassas Chrysler/Jeep. Those of you with a “Lifetime Powertrain” warranty will of course want to call and inquire.

Before you start, disconnect the negative terminal from the battery.

Remove the #4 and #6 spark plug wires at the spark plug end and lay them to the side.

In order to see the area where the cracks usually develop, you have to remove the two piece heat shield on the exhaust manifold. The lower half of the heat shield is held on with one 10mm nut that screws onto a stud mounted to the manifold. Remove the nut and the lower half of the shield using the 10mm wrench.

The upper portion of the shield is held on by two of the exhaust manifold to cylinder head mounting bolts. Using the 10mm swivel socket and long extension, remove the two 10mm bolts and then remove the upper portion of the heat shield. This is what you will probably see if you suspect an exhaust leak.

I decided to do the write-up for anyone thinking of saving themselves some cash, for those who might just want to try it for themselves and for beginners. It’s a pretty easy job to replace the manifold using only hand tools. However, as we all know, there is Murphy’s Law to consider. If one of the bolts that hold the exhaust manifold to the cylinder head strips or breaks off in the cylinder head, it WILL be a royal PITA to fix and could possibly involve removing the cylinder head to extract the broken bolt or repair the stripped threads! PLEASE weigh these possibilities carefully before you decide to do this yourself. It could get pretty darn expensive if you cannot dig yourself out. At this point, if you decide not to DIY, at least it will confirm if you have a problem or not. It's a simple matter to reinstall the two bolts, the heat shield and take it to someone who can take care of it for you.

Here we go:
Unfortunately, I didn’t take photos until everything was going back together.

Tool list:
3/8” ratchet
24” 3/8” extension
3/8” x 10mm swivel socket
3/8” x 15mm swivel socket
Inch pound torque wrench
Vise grips (or another set of hands)
10mm wrench
Small wire brush
Permatex Anti-Seize (or high temp anti-seize of your choice)
PB Blaster (or penetrating oil of your choice)
Gum Cutter (or solvent of your choice)

Parts list:
Exhaust manifold PN/4666024AD
Exhaust manifold gasket PN/4892409AA

Foot pound torque wrench

Taking your time, it will probably take around 2 hours or less if everything goes well. If you encounter seized or broken bolts….who knows.

Spray the bolts and clip nuts holding the exhaust pipe to the manifold the night before if you can. I didn’t bother spraying the manifold bolts.

Again, if you haven't already, remove the negative terminal from the battery.

Remove the two 15mm bolts holding the exhaust pipe to the manifold from underneath the jeep using the long extension. If you are not lifted, you will want to raise the jeep up to make this easier. It’s a little bit of a pain to get to the bolts but there is just enough room to do it.

The nuts for the exhaust pipe bolts are held in place by clips.

One of mine was stubborn. It twisted in the clip and was spinning as I tried to loosen it. Fortunately, there was enough room to clamp the nut to the manifold flange with a pair of vise grips.

If you haven't already, remove the #4 and #6 spark plug wires at the spark plug end and lay to the side.

Now remove the remaining 10mm exhaust manifold bolts with the long extension and the 10mm swivel socket.
The rearmost bolt closest to the firewall is fairly difficult to get to. Make sure you try your best to get in to it as straight as possible. If you put the swivel in too much of a bind you could possibly break the head of the bolt off. I read of several people who either found the bolt broken or broke it during removal (it was unclear to me). Once the bolts are removed the manifold will wiggle out easily.

Carefully clean around the cylinder head exhaust ports. I used Gum Cutter on a rag and wiped most of the carbon off easily. You just want to make sure the surface is clean. Make sure nothing falls down into the exhaust ports while they are exposed.

Take a peak at the upper catalytic converter while you’re at it. It should look uniform and in one piece. If it’s broken in pieces or appears melted you’ve got a problem.

Use the Gum Cutter on a rag and wipe down the face of the exhaust manifold where the ports are and where the exhaust pipe contacts the collector.

The manifold gasket from Mopar is high quality and should only be installed one way. The side that faces the manifold is clearly marked.

Now is a good time to clean up all of the bolt threads with a small wire brush and apply a thin coat of anti-seize to the threads. Also make sure the 2 clip nuts are in good shape as well. I had to reform the metal clips to hold the nuts securely.

Place the manifold on top of the exhaust pipe opening and close to the cylinder head. Carefully slip the gasket in between the exhaust manifold and cylinder head. Using one of the 10mm bolts, line everything up and start the bolt into the cylinder head being careful not to cross thread it. Start it by hand or use just the socket to start it. Just put a couple of turns on it until the manifold and gasket are supported. Carefully start the other 10mm manifold bolts except for the two that retain the upper portion of the heat shield.

Starting in the middle of the manifold and working your way out, snug the bolts to the initial torque of 25 inch pounds.

Place the clip nuts on the exhaust manifold flange and line them up with the holes. Now take a 15mm bolt and thread it up through both flanges into the clip nut above. It takes a bit of contortion but you can do it. It may be easier to do it from underneath with the long extension if you have help up top.

Thread each bolt in evenly a little at a time so you don’t cock the flange on the exhaust pipe. If you do, the exhaust pipe may not seal properly to the bottom of the exhaust manifold. Snug the bolts up nice and tight and torque to 30 foot lbs.

Install the upper portion of the heat shield with the last two 10mm bolts and, working again from the middle out, torque all 10mm manifold bolts to 200 inch pounds.

Install the lower portion of the heat shield on the manifold stud with the 10mm nut.

Install #4 and #6 plug wires.

Reconnect the negative terminal from the battery.

Start the engine and check for exhaust leaks. Listen closely, see if you can smell exhaust and run you hand around the spots where it could leak before everything gets too hot.

Test drive and you’re done. Hopefully you have saved yourself a couple hundred bucks.


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