Duramax Head Gasket Replacement

[DmaxMaverick]

That little hose section behind the fan pulley is the turbo coolant supply. I've replaced mine twice, as well as a bunch of others. Not too complicated or difficult (replaced one in an RV park in less than an hour, once). I prefer the OEM spring clamps, as well, but used screw clamps the last time I replaced the line. I double-clamped it (4 clamps, 2 at each end), and it hasn't leaked since. I reused the OEM spring clamps the first time, and it began weeping rather quickly. As far as I know, mine wasn't/isn't pressurizing the coolant system, such as with a head gasket leak. GM/Duramax surely could have located the soft connection in a better place.

[More Power]

That little hose section behind the fan pulley is the turbo coolant supply. I've replaced mine twice, as well as a bunch of others. Not too complicated or difficult (replaced one in an RV park in less than an hour, once). I prefer the OEM spring clamps, as well, but used screw clamps the last time I replaced the line. I double-clamped it (4 clamps, 2 at each end), and it hasn't leaked since. I reused the OEM spring clamps the first time, and it began weeping rather quickly. As far as I know, mine wasn't/isn't pressurizing the coolant system, such as with a head gasket leak. GM/Duramax surely could have located the soft connection in a better place.

Thanks... Second the notion that GM could have located that hose somewhere with a little better access...

I may try a double screw clamp. The end with the best access is the one oozing.

By the way... And for everyone else, that hose is a 10mm internal dimension coolant hose. It looks like it may be 3/8", but 3/8" is a little small. The hose can be saved by squirting a little coolant on the pipe it is attached to and once the clamps have been loosened, work/move the hose all the way to the left (as you're facing the front of the engine). That should get you enough latitude to remove the coolant pipe that carries coolant to the turbocharger, or replace the hose/clamps if need be.

[More Power]

It's now been a little over 2 years, and the truck has accumulated nearly 13,000 miles since my daughter and I replaced the head gaskets, injectors and injector fuel lines, and resealed the injector cups, resurfaced the head decks and set the valve lash in my 2001 GMC's Duramax 6600. The truck continues to run great, and there has not been a single issue with the head gaskets or any other aspect of the tear-down and re-assembly (other than a minor fuel and coolant leak after the initial startup the first day after the service - that were easily taken care of). None of the head gasket service videos that I've seen online talk about how successful their repairs were over time. A rather important point, considering the "dubious" repair procedures shown in the videos... So, other than to share a little of Montana with you, that's the reason for this update - to talk about the success of the head gasket replacement project that was completed in June of 2021 - done the right way.



Nearly a hundred miles from home, this pic was snapped on Thursday, August 10th looking north from an overlook situated above the southern end of the beautiful Flathead Lake here in western Montana. Just over the hill and to the left a couple of miles is the small town of Polson, Montana. However, our destination that day was to the right in this photo, on the eastern shore of the lake, to a public facility called Finley Point State Park. We had rented a cabin there for a few days. This trip was possible because the new head gaskets have made the truck a reliable member of the family again.

Flathead lake is among the largest freshwater lakes in the country, being 28 miles long, up to 15 miles wide, and 370 feet deep at its deepest point. The scenic value of this natural wonder is awe inspiring, especially when set against the glacially carved and rugged Mission Mountain Range just off camera to the right. This mountain range reminds me of the glacially carved topography found in Yosemite. Flathead Lake is the result of a very large glacier that had scooped out the lake bottom during the last ice age. This elevated overlook where the truck is sitting is a "terminal moraine" that had been bulldozed into place by that glacier, and which also defines the southern boundary of the Continental Ice Sheet that once covered all of Canada and a northern fraction of what would become the US's lower 48.

We were here, partly, to kayak and to try our hands at fishing. Flathead Lake contains Lake Trout up to 40", good sized Lake Whitefish, Kokanee salmon and several other species (bass, perch, etc). My experience with fishing the lake was pretty limited, but the Zimmerman bait/tackle shop in Ronan, MT set us up with a selection of the right gear, and showed us a chart with water depths describing where each species would be located. This time of year, the bigger fish are all in deeper water, so my daughter and I jigged for Whitefish using artificial lures in about 100-150 feet of water - offshore from Blue Bay. I caught one and had several others on the line. The Whitefish we battled were about 2+ lbs and about 24" in length. Though the limit was a hard-to-imagine 100 per day, we were just catch-release fishing. We found the Whitefish to be hard fighters when using light tackle, and when in a kayak!

We had beautiful weather this trip, and the many cherry orchards around the lake had produced a bountiful crop - there were many open fruit stands all along the roadways. The large Bing cherries were delicious! My daughter even fed a few cherries to a Whitetail doe and fawn just a few feet off the front porch of our rented cabin.

See my signature below for a link to a page that describes our printed and bound Duramax Diesel Service Guide book, which includes a number of service procedures for the Duramax 6600 - including a head gasket replacement project. Do it once, do it right.

Jim Bigley

PS - The name "Flathead" came about because of a native tribe that once inhabited this area. Their custom was to bind boards against the heads of younger members of their group, thus modifying their skull shape over time. This was similar to what was practiced by a few native tribes found in both North and South America.

Today, the southern half of Flathead Lake and continuing south for another 50 miles is all within the boundary of the beautiful Flathead Indian Reservation. There is much to see and do within the Reservation, and I encourage those visiting this area to take advantage of the opportunity. Fishing on the reservation requires a reservation permit - available at any license counter here in western Montana or online.

I've known and even worked with a few natives from this area - going back to when I was a teen, and up through the 1990's when I assisted their tribal college to complete the setup and repair of some science tech I was trained for at the University of Montana. We met and talked with a handful of natives during this August 2023 visit. They're still the real deal... This area is a bright spot among Indian reservations. It's beautiful here. You'll be blessed for having visited.

[arveetek]

Thanks for sharing, Jim! You definitely live in a beautiful part of the country. I've never been able to visit Montana, but it's on my to-do list.

Casey

[More Power]

I've mentioned here before that Youtube can be a fun place to hang out or learn something you didn't know. However, when it comes to working on your Duramax 6600, a little common sense can go a long way. Back in 2021, I did a search on YT about Duramax 6600 head gasket replacements... I found the most popular video in the list of those I watched to be one where the mechanic was using a horrible technique to prepare the block deck for new gaskets... Here's a screen grab. Yikes!



The above image would be appropriate if he was grinding off a half inch of body filler - but this is not appropriate prep for new head gaskets. To compound the problem, there is absolutely no attempt to prevent carborundum grinding grit and debris from falling into the lifter galley, onto the piston crowns or into the cooling passages. This is NOT how GM specifies the heads and block decks are to be prepared...

The next image shows what IS recommended by GM - to help prepare the Duramax 6600 head and block deck surfaces.



This is a 3"x4" steel block that was machined flat on a milling machine. GM recommends using a light oil (I used WD-40) with 600-grit wet/dry paper on the pictured steel block to prepare the cast iron block and aluminum head deck surfaces. I also stuffed the lifter galleys and piston crowns with clean shop rags, and any accumulating oily sludge was prevented from entering the cooling passages. Our Service Guide linked-to below shows how this is done.

The Duramax 6600 head gaskets require a certain smoothness for both the block and head deck surfaces. The design of the head gaskets require this smoothness, and the differing temperature coefficient of expansion between the aluminum heads and cast-iron block demands it. 600-grit provides that smoothness, when used with an absolutely flat steel block.

I had a local fabricator make this block for me, but you could create your own by using a 4" length of 3" steel angle iron. Then make it flat by using a series of coarse/fine grit wet/dry sand paper sheets on glass or a flat counter top. Round the edges before completing the job - so they can't dig into the aluminum heads.

The job of preparing the heads and block isn't that difficult and it goes pretty fast. Jim

[a5150nut]

I have found if i watch 5 or 6 YT Videos i can find something in one and something else in another. They all seem to leave out a little something that was critical or that made things easier.
But for the price you cant beat it

[More Power]

I have found if i watch 5 or 6 YT Videos i can find something in one and something else in another. They all seem to leave out a little something that was critical or that made things easier.
But for the price you cant beat it

You're right. Though, discernment comes with experience. The video mentioned above was about an hour long - for a project that takes 40+ hours to complete (GM labor rate), so there's a lot left out - a lot of questions unanswered. And, certainly most of the hard parts of the job are left out - the same hard part(s) are left out in each video (I have a theory for why that's so). I watched several other videos for this topic, but found none gave the complete story - a proper story. The video channels all produced content that relied on the viewer to already have a good understanding of auto mechanics in general and Duramax head gasket replacement in particular - when in reality none do. These engines and fuel injection systems are complicated - risk of failure is significant, and the video creators never give the viewer a long-term follow-up. What's the price of failure or chronic nagging complications?

I know a local Duramax owner who abused his stock Duramax till coolant leaked/poured out in several places (i.e. head gaskets, water pump seal, coolant surge tank overflow, etc). He then hired a local shop to build him an "indestructible" 1000-hp monster - forged pistons, aftermarket rods, big injectors, dual CP3 pumps, twin turbos, etc. It only lasted a couple of months, after the truck owner spent $20K on it. Knowing the story, I blame the shop for the eventual outcome and partly on not properly managing expectations... An idiot behind the wheel can ruin just about anything. In the end, it boils down to experience...

[More Power]

I watched a Duramax engine-related video short last evening that was created by a white haired guy in a professional looking shop. The video focused on a Duramax 6600 engine sitting out of the truck with its heads removed. In that video, the white haired guy pointed to the top of a Duramax piston that had been partially melted by what he described as an injector failure. He said this extreme heat had damaged the piston crown and caused the piston to swell in the cylinder, resulting in both piston damage and cylinder damage.

Individual common-rail injectors can fail in ways that cause it to become a fierce blowtorch - a piston melting blowtorch. But, in my opinion, an injector failure wasn't the root of the problem in that video short. What he didn't point out was that other pistons also showed evidence of extreme scorching, produced by excessive fueling, which resulted in EGT temperatures well in excess of 1300 degrees F (maybe even 1500 degrees F). This scorching always produces a distinct and pronounced star pattern on the piston crowns - the melted piston in the video had that scorched star pattern on it. Think about what a Saturn 5 launch pad must have looked like after a moon shot.

My opinion, based on the images, was that the truck owner installed high-flow injectors and ran with a big program that put a lot of fuel into the engine. He then raced or pulled with it, which produced a combustion temperature that the piston(s) couldn't cope with.

The point... I believe the video producer didn't correctly diagnose or describe the problem... I found it curious that the shop owner didn't take the time to show the viewers what the other pistons looked like, and how he characterized their appearance. The video only showed an adjoining cylinder very briefly and incidentally - curious... Truck owners (and video viewers) need to know the whole story of what happened, to help them avoid a problem like that shown in the video. This must have been at least a $10,000 repair.

By way of comparison, here's what a normal Duramax piston crown looks like in a stock daily driver with 140,000 miles on it. There's only the faintest of star pattern on the outer rim, with no star pattern on the bowl.



In closing, a common-rail injector that fails in a way that allows it to spray unregulated amounts of fuel will likely set a cylinder balance code, will smoke at idle (and above), will run rough and excessive blow-by will huff white smoke out the oil fill pipe with the cap removed - if the engine is run long enough to damage a piston/cyl. I'm not sure how this would affect fuel rail pressures at idle, but I suspect there also may be low rail pressure codes. In other words, a Duramax owner should have ample warning that a serious problem exists - possibly even before damage has been done. An exception to this might be when a Duramax is being used to tow heavy while out on the highway, and the driver simply can't pull over/stop immediately due to safety concerns - he has to keep going. In this situation, it becomes a choice between dollars and sense.

Maybe someone who has experienced this sort of problem with their truck can help fill in the blanks on symptoms. Jim

[More Power]

https://youtube.com/shorts/pySyCI1lR...HunvXKqYnAoKzp

I know that the debate regarding whether to choose head studs or head bolts for a Duramax 6600 will likely never be completely resolved, but here's another voice that addresses the question...

I like Gale Banks. I've met him personally a couple of times, had dinner with him, and we've talked on the phone/email. But... Now, to be fair, the image he uses in this video of block deck bolt thread failure is NOT of a Duramax 6600. I don't know what engine is represented by that pic. You can see in the image in a previous post (of mine) what the block deck actually looks like in a Duramax 6600. The bolt holes are much different, and far less likely to fail like that shown in the Banks video.

Still... I believe Banks would be running studs and selling his own stud kits if he thought studs were either necessary or even just a better choice. Studs are a fairly expensive option. Gale is a businessman...

[Robyn]

I agree.
But Gale Banks has not been known for peddling "Goody yum yum" parts simply to make $$$$
Gale has always worked to deliver fixes to real problems......

I have never met Gale buy have used some of his parts....Always top shelf stuff

[More Power]

I agree.
But Gale Banks has not been known for peddling "Goody yum yum" parts simply to make $$$$
Gale has always worked to deliver fixes to real problems......

I have never met Gale buy have used some of his parts....Always top shelf stuff

I believe that if Banks thought (or could show that) head studs provided a justifiable benefit, he'd be selling his own - "he is a businessman" after all.

Still... I wish Banks hadn't used a non-Duramax 6600 block deck pic to try to make a point about weak threaded holes in a block deck. That pic wasn't necessary. In my opinion, Banks' opinion/in-house testing is enough to make the point. I trust him.

Studs, however, do have one real advantage over TTY head bolts... Studs are reusable. But... you can buy 3 sets of TTY bolts for the cost of one set of ARP-2000 head studs. This reusable advantage might be important for racers who are inside their engines on a regular basis, but not so much for a grocery getter, commuter, or RV/boat hauler.

As discussed in our Duramax Service Guide, the fire-ring on these head gaskets tend to Brinell (create an impression in the aluminum head decks) over time due to the clamping load of the head fasteners. Both the factory TTY bolts and the ARP studs are torqued to the very same level - 125 ft/lbs. I measured the final torque of the TTY head bolts using a torque wrench during the final TTY angle sweep during installation. And, I installed a set of ARP head studs during another of the Duramax head gasket projects I did a couple of years ago. So... studs aren't being used to add more clamping load, because that would create a deeper fire-ring impression into the aluminum head decks.