Duramax Head Gasket Replacement: ‘04.5 LLY

Duramax Head Gasket Replacement

When GM introduced the Duramax diesel in 2001, it was truly a
state-of-the-art engine. Since its introduction, the Duramax has
gone through LBZ, LLY, LBZ, LMM, and LML designations, with a
number of revisions along the way. While all iterations are fairly
reliable, the older ’01-’04 LB7 engines and ‘04.5-’05 LLY’s are
starting to show their age. Blown head gaskets are fairly common
in these earlier year trucks, as wear and tear, aftermarket tuning,
and high mileage are all contributing factors to failure.

To get the down-low on replacing Duramax head gaskets the right way, we tagged along with Jason Carrier at Xtreme Diesel Performance in Chico, California, to see how it was done. The truck in question was a ‘04.5 LLY, which thanks to heavy towing and a hefty tune, was in need of a new head gasket. The truck had started using coolant, a little at first, and then almost a quart a week. It was clear something needed to be done ASAP before anything else got hurt, so the truck was immediately put under the knife.

One thing to remember about a head gasket job on a Duramax is that it’s very labor-intensive. Book time is nearly 40 hours of labor, which means that there’s usually nearly $4,000 in labor alone. Since it’s not something you want to do twice, Carrier walked us through some tips and tricks during the installation that will ensure the engine’s gaskets will last for decades to come. DW

The first step to a Duramax head gasket replacement involves draining the coolant, and removing the upper fan shroud. Luckily, the radiator is still one thing that can be left in place.
Xtreme Diesel owner Jason Carrier is always careful to put everything back exactly how it came off, including the fan belt. “Belts have a wear pattern, just like tires,” notes Jason.
Virtually all of the engine accessories have to be removed in order for the cylinder heads to come off. This includes the alternator, a/c compressor (which can just be moved to the side) as well as the idler bracket and pulleys (shown).
To save time, Carrier removes systems in one piece whenever possible. Although it doesn’t look like it, the driver’s side charge pipe can be completely snaked around everything without taking anything off of the driver’s side head.
By now all of the coolant should have drained out, which means that the upper hard hose and coolant crossover can be removed.
With the front of the engine starting to come apart, it was time to move on to the passenger’s side wiring harness. This must be (carefully) removed in order to gain access to the upper valve cover of the engine.
Next, Carrier removed the EGR system. If you look closely, you can see a good amount of buildup, which will all have to be cleaned off before the system is reinstalled.
With the EGR and wiring out of the way, it was time to start working on the injectors, lines, and upper valve covers.
Before the upper valve cover could come off, the engine’s injector lines, injector harness, glow plugs, and injectors all needed to be removed. An injector puller is one of the few specialty tools that’s needed for the job.
After the upper valve cover is removed, the lower valve cover can be taken off, which exposes the engine’s valvetrain.
Once he completed the passenger’s side, Carrier moved on to the driver’s side of the engine, where it was wiring, glow plugs, lines, and injectors all over again. With both valve covers off, it was now time to start removing the engine’s valvetrain, starting with the rocker arm assembly.
The pushrods are the next valvetrain part to be removed, which are then cleaned and kept in the same order for re-installation.
It’s been a long road, but it’s time for the cylinder head to be removed! Notice that the back bottom bolt on the driver’s side can’t be removed without it hitting the firewall. Carrier says that the trick is to just loosen that bolt, then pull it out at the same time the head is removed.
Time for the heads to be removed! Both the driver’s side and passengers’ side heads are taken off, leaving the engine a bare-bones short block plus turbocharger.
Upon close inspection, it was easy to see the distorted area where the factory head gasket blew, and had been leaking large amounts of coolant.
“Never reinstall the factory heads without having them checked and surfaced,” Carrier says. Both cylinder heads were sent off to Terrill’s Aluminum Cylinder Heads in Chico, California, to be checked for cracks, cleaned, and surfaced. Both heads came back with only minor work needed, and looked as good as new.
With the engine bay looking quite bare, it was time for the decks to be cleaned on the block, and both heads and gaskets to be reinstalled.
For reinstallation, Carrier uses a complete head gasket kit available through Merchant Automotive, in Zeeland, Michigan. This kit includes two multi-layer steel (MLS) gaskets, as well as all the other assorted gaskets and hardware needed to complete the job. Carrier notes: “There’s a right and left side head gasket, and you definitely don’t want to get in a hurry and mix those up.”
Also included in the Merchant kit are a new set of head bolts, which will replace the decade-old factory hardware. Customers can also upgrade to ARP studs, but Carrier stated that it “…wasn’t needed in this application.”
“It’s a lot easier to assemble one side at a time so you can stay focused,” notes Carrier. “A lot of people over-torque bolts or studs, but I’ve found that the factory torque-angle method is more than adequate,” contunes Carrier.
With the driver’s side head torque down, it was time to move on to the passenger’s side. Once both cylinder heads were on, it was time to re-assemble the valvetrain.
“You can’t just bolt on the rocker arms and go,” notes Carrier. “All of the valves need to be re-adjusted to factory lash specs before assembling the rest of the engine.
With the valvetrain installed, both upper and lower valve covers can be installed, as well as the engine’s injectors. “The injectors and glow plugs are one of the first things I install, so additional debris can’t get into the engine,” notes Carrier.
With the newly machined heads, valve covers, and valvetrain installed, it was starting to look like an engine again! Unfortunately, the complexity of the Duramax engine meant there was still a long way to go.
Remember about the first 15 disassembly steps? Well, everything that came off now needed to go back on. “Everything installs in a certain order and lays in a certain way on the Duramax engine,” says Carrier. “If it doesn’t feel right when you’re putting it back on, you’re probably doing something wrong,” he says.
In this second shot, you can see exactly how many components need to be re-installed for the engine to operate again. After about 3-4 hours of work from the valve cover-on point, the engine was ready for a final few intake and exhaust pieces and coolant.
“The factory intake on the LLY is very restrictive, so we always recommend an intake upgrade whenever we work on them,” says Carrier. “This S&B piece is a vast improvement compared to the stock version, which chokes out the turbo under high loads,” says Carrier.
With the intake and exhaust back on, it was time to hit the road. “With head studs, you might want to re-check and re-torque them if needed, but with the bolts, we could just let the engine warm-up and then go,” continues Carrier. “The LLY’s don’t have the injector problems that LB7’s do,” notes Carrier, “So after the head gasket fix, this should be a reliable truck for years to come.”

Why does it take so long??

A lot of people are incredulous that a Duramax head gasket job can take so long, so we kept track of everything that needed to be removed or disconnected and reinstalled in order to replace the head gaskets. Ready? In no particular order…

Valve covers
Exhaust manifolds
A/C compressor
Wiring harness
Fan shroud
Charge pipes
Intake crossover
Coolant bridge
Injector lines
Fuel lines
Idler pulley
Rocker arms
Glow plugs
Fuel rails
Fuel filter
Engine drivers/computers

Whew! Now you know why it takes so long.

Merchant Automotive

S&B Filters

Terrill’s Aluminum Cylinder Heads

Xtreme Diesel Performance

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