Customer 
Duramax has had several classifications since its launch, including LBZ, LLY, LBZ, LMM, and LML. Several changes were made along the road. All versions are rather dependable, however the older LB7 engines from 2001 to 2004 and the LLYs from 04 to 2005 are beginning to show their age. These earlier model vehicles frequently have blown head gaskets because of excessive mileage, aftermarket tune, and general wear and tear.
We started with learning the inside scoop on changing Duramax head gaskets correctly. The vehicle in question was a ‘04.5 LLY that required a new head gasket because of excessive hauling and a high tune.
The truck had begun to use coolant; it was almost a quart every week at first. The truck was taken under the knife right away since it was obvious that something had to be done quickly to prevent any further injuries.
One thing to keep in mind is how labor-intensive replacing the head gasket on a Duramax is. With a book time of around 40 hours of effort, the labor alone often costs close to $4,000.
1. Draining the coolant and removing the top fan shroud are the initial steps in replacing the Duramax head gasket. Fortunately, one item that may still be left in place is the radiator.
2. Take care to replace everything just as it was taken apart, even the fan belt. Similar to tires, belts too exhibit a wear pattern.
3. To remove the cylinder heads, almost all of the engine’s accessories must be taken off. This comprises the idler bracket and pulleys (shown), the alternator, and the air conditioner compressor (which is just movable to the side).
4. Eliminate systems in their whole system whenever feasible to save time. Despite appearances to the contrary, everything can be fully wrapped around the driver’s side charge pipe without removing anything from the driver’s side head.
5. It should be possible to remove the top hard hose and coolant crossover at this point as all of the coolant should have drained out.
6. It was now time to tackle the wire harness on the passenger’s side of the engine, as the front was beginning to fall apart. This has to be (gently) removed in order to reach the engine’s upper valve cover.
7. Then take off the EGR system. There appears to be a significant quantity of buildup, which has to be removed before the system is reinstalled.
8. It was now possible to work on the injectors, lines, and top valve covers once the EGR and wiring were removed.
9. The engine’s injector lines, injector harness, glow plugs, and injectors had to be taken out before the upper valve cover could be removed. For this task, one of the few specialized instruments required is an injector puller.
10. The engine’s valve train may be seen once the lower valve cover has been removed, following the removal of the upper valve cover.
11. Now work on the driver’s side of the engine after finishing the passenger side, repeating the process with the wiring, glow plugs, lines, and injectors. Now that both valve covers were removed, the engine’s valve train needed to be disassembled, beginning with the rocker arm assembly.
12. It has been a lengthy journey, but the cylinder head has to be taken out! It is evident that the driver’s side back bottom bolt cannot be removed without contacting the firewall. The secret is to simply undo the bolt and extract it concurrently with the head removal.
13. It’s time to take off the heads! With the removal of the passenger and driver’s side heads, the engine is reduced to a simple short block with a turbocharger.
14. The deformed region where the stock head gasket broke and substantial volumes of coolant leaked was easily visible upon close inspection.
15. We always advise against reinstalling factory heads before having them examined and surfaced. We received both cylinder heads and had them surfaced, cleaned, and inspected for cracks. After just minimal adjustments were made, both heads returned to their original appearance.
16. It was time to clean the decks on the block and replace the gaskets and heads as the engine bay appeared to be quite empty.
17. Employ a full head gasket kit for reinstallation. Two multi-layer steel (MLS) gaskets and all the other gaskets and hardware required to finish the project are included in this package.
18. This kit also comes with a fresh set of head bolts to replace the factory hardware that is ten years old. ARP studs “weren’t needed in this application,customers can still upgrade to them.
19. It was now time to go to the passenger’s side head torque once the driver’s side had finished. After the installation of both cylinder heads, the valvetrain needed to be put back together.
20. The rocker arms cannot be simply installed and removed. Before putting the engine’s remaining components together, each valve must be re-adjusted to meet factory lash specifications.
21. The engine’s injectors and upper and lower valve covers may be added after the valvetrain is in place. One of the first things we install is the glow plugs and injectors to prevent further junk from entering the engine.
22. It was beginning to resemble an engine once more with the installation of the freshly machined heads, valve covers, and valvetrain! Sadly, there was still more work to be done due to the Duramax engine’s complexity.
23. Do you recall the first fifteen stages of disassembly? All that had been taken off now had to be put back on. On the Duramax engine, everything fits and installs in a certain order. You’re most likely doing something incorrect if it doesn’t feel comfortable when you put it back on.
24. This second image shows you just how many parts must be replaced in order for the engine to start up again. After working on the engine for three to four hours from the valve cover-on point, the engine was prepared for the last few intake, exhaust, and coolant components.
25. Every time we work on an LLY, we always propose an intake upgrade because the stock intake is highly restricted. When compared to the factory version, which chokes out the turbo at heavy loads, this S&B component is a huge improvement.