Rear Main Seal

A common issue with Jeeps is a rear main seal leak. You know you have it when you see drops of oil on your driveway that are just behind the engine. You've tried the quick fixes such as using high-mileage oil or adding STP Stop Leak to your oil, but you still have an an oil leak. Fortunately, the rear seal on Jeeps is a two piece seal that can be changed without removing the engine or transmission. This article shows the process that I used when changing the seal on my 2000 Jeep Wrangler TJ.

This repair took me about 15 hours over a three day period. Most people will be able to go much faster because they won't be taking pictures and recording the steps. Even so, I would still set aside two days for the project so that the oil pan gasket has time to dry.

Here are the steps described in this article:

• Remove the battery
• Remove the starter
• Drop/Push aside the exhaust
• Remove the oil pan
• Remove the rear main cap
• Replace the rear main seal
• Put it all back together

The parts/materials that you'll need are:

• Two piece rear main seal which can be found at your local auto parts store
• A one piece oil pan gasket
• Some RTV sealant to seal the ends of the rear seal and to help hold the oil pan gasket on

There are no special tools for this project. Just your standard set of sockets, both SAE and metric, various socket extensions to help reach the exhaust manifold bolts, a drift to help remove the seal, etc...

Step 1 - Disconnect The Battery

As with most projects that involve you with your hands wrapped up in the engine, you'll want to disconnect the negative (black) battery terminal. I would also tape the negative terminal with electrical tape to reduce the chance of any mishaps.

Step 2 - Jack Up the Jeep

Jack up your Jeep and put it on jack-stands. You are going to be under the Jeep for a long time so make sure everything is good and solid.

Step 3 - Remove the Starter

You could probably get by without doing this step, but some of the oil pan bolts are difficult to get to when the starter is in. Since there are only 3 bolts and a screw to worry about to remove the starter I would recommend doing this to give yourself more room to work. Please refer to the starter replacement article for details about removing your starter.

Step 4 - Remove the Exhaust

This step may differ for different Jeeps depending upon how your exhaust is installed. In my case, there are no flange nuts at the catalytic converter so I kept the exhaust completely together and just pushed it aside. This isn't a bad way to go because it minimizes the chances of an exhaust leak. In other Jeeps, it might be possible to remove the exhaust pipe from the catalytic converted and from the exhaust manifold.

Before proceeding with the exhaust removal, you will need to remove the transmission cross-member to give you better access to the oxygen sensors and to provide more room to move the exhaust. Refer to the removing your transmission cross-member article for details. The remaining steps assume you've removed the cross-member.

Once the cross-member is out of the way, unplug the rear oxygen sensor wire. This sensor is the one behind the catalytic converter. The wire leads to a holder and clamp that is on the transmission, it was easier to remove clamp from the wire than to remove the O2 sensor.

Tie the sensor wire to the exhaust with a tie-wrap to avoid damaging the wires.

Next, unplug the oxygen sensor that is front of the catalytic converter. This sensor also has a wire connector that can be removed. Tie wrap the wire to the exhaust pipe.

Now, we need to remove the exhaust manifold. The picture below shows the manifold for a 6-cylinder. Notice there are four bolts that will need to be removed. These bolts took me and a friend about 3 hours to get out because the nuts on the upper side are difficult to get a good grip on.

Here is a picture of what the bolt and nut looks like once removed. Notice there isn't much to grab with an open or box-end wrench. They are supposed to not require a wrench on the top, but in my case the tab bent up because the bolts where stuck on so hard. Definitely, spray the bolts and nuts with some kind of rust loosing spray before going after them. We used a combination of vice grips for two of them and a box end wrench for the others. This was probably the biggest time-sink of the entire project. As a hint, since the cross-member is out, you can adjust the angle of the engine by raising or lower the transmission to give a little better access to the top nuts. If you're lucky, the anti-rust spray will work and the bolts will come right out.

Once the exhaust manifold bolts are out, remove the exhaust bracket at the tailpipe to allow the exhaust to be pivoted on the center bracket. Once the tailpipe bracket is removed the exhaust can be rested on the floor. I don't have a picture of the middle bracket, but it might also help to remove it. I was able to move the exhaust around while it was connected to the middle bracket, but when I reinstalled the exhaust, I ended up removing the bracket to make it easier.

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