Attention: TDR Forum Junkies 
rbattelle
TDR MEMBER
This is not a hard job, by any means, but I thought I'd post a little "how to" since it's common for these to leak a bit. Mine began leaking during cold weather after 65k miles.
Thanks to HOBrian for his tips.
Before you begin, remember that you're about to perform open heart surgery on your expensive engine. So cleanliness is important! I cleared out plenty of room on my bench to put the rocker box and the valve cover while I worked on them.
You'll need the following tools:
-Some plastic bags to store bolts as you remove them. This will prevent losing any bolts.
-Some fresh clean engine oil to lubricate the o-rings. A little squirt bottle is convenient.
-Various sockets (10mm and 8mm, to be specific). You're going to need smaller size tools - 3/8" and 1/4" drive - to make it easier to access bolts at the back of the engine.
-In*lb torque wrench.
-Shop towels (preferably the lint-free variety).
-Q-tips are handy for cleaning up o-ring grooves.
For safety, disconnect the negative terminal of both batteries before beginning.
Disassembly
1. First, remove the plastic vanity cover from the top of the engine (photo 1). It uses 4 M8x1. 25 bolts with 10mm heads.
2. Remove the hoses from the breather filter (photo 1). I've provided arrows which indicate the breather hoses removed, the front 2 valve cover bolts, and the first injector electrical connector.
3. Unbolt the valve cover. There are 6 bolts, all M8x1. 25 with 10mm heads. Each has an o-ring around it for sealing. The cover should come of pretty easily. It uses a reusable rubber o-ring that sits in a groove in the cover itself. Set the cover aside in a clean place. I took a little time and cleaned up the top of the cover, which was pretty filthy.
Now you're looking at the job: the valve train is open, and the rocker box is in place (photo 2). I've provided arrows that indicate the 7 bolts securing the rocker box (the one at the front and way at the back are not visible in the photo, but the arrows are provided nonetheless). The 5 bolts in the middle are long-length, the two on the ends are short. All are M8x1. 25 with 10mm head. The last photo also provides an overview of the rocker box itself, in case you're not clear on what exactly we're after here.
4. Remove the injector solenoid wires (photo 3). These are integral to the rocker box, so they'll remain attached to the box. In addition, the nuts are captive to the wires, so there's no fear of losing one!
I recommend writing yourself a note describing the proper positioning of the wires, even though they'll pretty much only go back together one way. These are not going to be separated from the rocker box, but just in case it's worthwhile to know precisely where each wire goes. Notice they alternate colors: yellow-orange-brown-red-yellow-orange-brown... and so on. The nuts use an 8mm socket (not sure what the threads are).
5. Disconnect the 3 injector pigtails alongside the rocker box (photo 4).
6. Remove the 7 rocker box bolts referred to earlier (photo 2).
7. It's nice to have an assistant here, although it's not necessary. Simply pull the box up off the cylinder head, ensuring the injector wires don't snag on anything. I found it useful to wire-tie the breather tubes out of the way.
8. Here's where I screwed up: I forgot to get a photo with the box removed. Sorry about that.
Just like the valve cover, the o-ring for the box is reusable (theoretically), and it sits in a groove machined into the underside of the box pretty tightly - you'll need to carefully pry it out with a small screwdriver.
Installation
9. Clean up the o-ring groove and apply a little engine oil to it. Then put the new o-ring in place and apply a little more engine oil to the o-ring itself. This will prevent the ring from twisting if you slide the box a little when reinstalling it.
10. When you're satisfied that the new o-ring is installed and lubricated properly, carefully lower the rocker box back onto the head. Again, this is where an assistant is very valuable (but not strictly necessary). Reinstall the 7 rocker box bolts and torque to 18 ft*lb (216 in*lb). I torqued to 205 in*lb and called it a day. Torque evenly from the center bolt and work out gradually. I torqued in 2 stages: 100 in*lb, then 205 in*lb.
11. Replace the injector wires. It will be pretty obvious which wires go to which injector, but if you get confused refer back to the notes you wrote earlier. The torque specification on these nuts is 13 in*lb, which is almost nothing. I used a little 1/4" ratchet and gently snugged them up.
12. Plug the 3 injector harness connectors back in (removed in step 5, photo 4).
13. Give the valvetrain a quick lookover to make sure you didn't leave rags, tools, or bugs in there.
14. Apply a little engine oil to the o-ring in the valve cover. Unless you're replacing it, it's not necessary to remove the o-ring from the valve cover (it probably won't just fall out on its own).
15. Again, it's useful to have an assistant help you replace the valve cover atop the rocker box.
16. Check the condition of the o-rings on the valve cover bolts. Replace them if they looked damaged (mine were fine). Apply a little engine oil to the o-rings before sliding the bolts into place.
17. Torque the 6 valve cover bolts (starting from the center 2) to 18 ft*lb. I used the exact same procedure I did for the rocker box bolts.
18. Reconnect the breather filter hoses.
19. Reinstall the plastic vanity cover. Torque specification is 18 ft*lb.
That's it! If all went well, whatever leaks you had should stop. Note, however, that it will take some time before all that engine oil you applied to the o-rings has a chance to leak off. Don't be surprised to notice the area a bit "wet" with oil for awhile.
It's an easy job. Cummins did a nice job designing the assembly. The hardest part is getting your tools access to the bolts at the very back of the engine under the cowl. Most of my stuff is 1/2" drive, which is difficult to fit between the cowl and the top of the engine.
I'm meticulous, so the job took me about 2. 5 hours, including cleaning up the valve cover. It's easily a 1-hour job if you're less of a perfectionist.
Thanks to HOBrian for his tips.
Before you begin, remember that you're about to perform open heart surgery on your expensive engine. So cleanliness is important! I cleared out plenty of room on my bench to put the rocker box and the valve cover while I worked on them.
You'll need the following tools:
-Some plastic bags to store bolts as you remove them. This will prevent losing any bolts.
-Some fresh clean engine oil to lubricate the o-rings. A little squirt bottle is convenient.
-Various sockets (10mm and 8mm, to be specific). You're going to need smaller size tools - 3/8" and 1/4" drive - to make it easier to access bolts at the back of the engine.
-In*lb torque wrench.
-Shop towels (preferably the lint-free variety).
-Q-tips are handy for cleaning up o-ring grooves.
For safety, disconnect the negative terminal of both batteries before beginning.
Disassembly
1. First, remove the plastic vanity cover from the top of the engine (photo 1). It uses 4 M8x1. 25 bolts with 10mm heads.
2. Remove the hoses from the breather filter (photo 1). I've provided arrows which indicate the breather hoses removed, the front 2 valve cover bolts, and the first injector electrical connector.
3. Unbolt the valve cover. There are 6 bolts, all M8x1. 25 with 10mm heads. Each has an o-ring around it for sealing. The cover should come of pretty easily. It uses a reusable rubber o-ring that sits in a groove in the cover itself. Set the cover aside in a clean place. I took a little time and cleaned up the top of the cover, which was pretty filthy.
Now you're looking at the job: the valve train is open, and the rocker box is in place (photo 2). I've provided arrows that indicate the 7 bolts securing the rocker box (the one at the front and way at the back are not visible in the photo, but the arrows are provided nonetheless). The 5 bolts in the middle are long-length, the two on the ends are short. All are M8x1. 25 with 10mm head. The last photo also provides an overview of the rocker box itself, in case you're not clear on what exactly we're after here.
4. Remove the injector solenoid wires (photo 3). These are integral to the rocker box, so they'll remain attached to the box. In addition, the nuts are captive to the wires, so there's no fear of losing one!
I recommend writing yourself a note describing the proper positioning of the wires, even though they'll pretty much only go back together one way. These are not going to be separated from the rocker box, but just in case it's worthwhile to know precisely where each wire goes. Notice they alternate colors: yellow-orange-brown-red-yellow-orange-brown... and so on. The nuts use an 8mm socket (not sure what the threads are). 5. Disconnect the 3 injector pigtails alongside the rocker box (photo 4).
6. Remove the 7 rocker box bolts referred to earlier (photo 2).
7. It's nice to have an assistant here, although it's not necessary. Simply pull the box up off the cylinder head, ensuring the injector wires don't snag on anything. I found it useful to wire-tie the breather tubes out of the way.
8. Here's where I screwed up: I forgot to get a photo with the box removed. Sorry about that.
Just like the valve cover, the o-ring for the box is reusable (theoretically), and it sits in a groove machined into the underside of the box pretty tightly - you'll need to carefully pry it out with a small screwdriver. Installation
9. Clean up the o-ring groove and apply a little engine oil to it. Then put the new o-ring in place and apply a little more engine oil to the o-ring itself. This will prevent the ring from twisting if you slide the box a little when reinstalling it.
10. When you're satisfied that the new o-ring is installed and lubricated properly, carefully lower the rocker box back onto the head. Again, this is where an assistant is very valuable (but not strictly necessary). Reinstall the 7 rocker box bolts and torque to 18 ft*lb (216 in*lb). I torqued to 205 in*lb and called it a day. Torque evenly from the center bolt and work out gradually. I torqued in 2 stages: 100 in*lb, then 205 in*lb.
11. Replace the injector wires. It will be pretty obvious which wires go to which injector, but if you get confused refer back to the notes you wrote earlier. The torque specification on these nuts is 13 in*lb, which is almost nothing. I used a little 1/4" ratchet and gently snugged them up.
12. Plug the 3 injector harness connectors back in (removed in step 5, photo 4).
13. Give the valvetrain a quick lookover to make sure you didn't leave rags, tools, or bugs in there.
14. Apply a little engine oil to the o-ring in the valve cover. Unless you're replacing it, it's not necessary to remove the o-ring from the valve cover (it probably won't just fall out on its own).
15. Again, it's useful to have an assistant help you replace the valve cover atop the rocker box.
16. Check the condition of the o-rings on the valve cover bolts. Replace them if they looked damaged (mine were fine). Apply a little engine oil to the o-rings before sliding the bolts into place.
17. Torque the 6 valve cover bolts (starting from the center 2) to 18 ft*lb. I used the exact same procedure I did for the rocker box bolts.
18. Reconnect the breather filter hoses.
19. Reinstall the plastic vanity cover. Torque specification is 18 ft*lb.
That's it! If all went well, whatever leaks you had should stop. Note, however, that it will take some time before all that engine oil you applied to the o-rings has a chance to leak off. Don't be surprised to notice the area a bit "wet" with oil for awhile.
It's an easy job. Cummins did a nice job designing the assembly. The hardest part is getting your tools access to the bolts at the very back of the engine under the cowl. Most of my stuff is 1/2" drive, which is difficult to fit between the cowl and the top of the engine.
I'm meticulous, so the job took me about 2. 5 hours, including cleaning up the valve cover. It's easily a 1-hour job if you're less of a perfectionist.
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