Duramax Head Gasket Replacement

[More Power]

5/31/2021: Well, I'm into it. Pulled the truck into the cleaned-out garage yesterday, and began the dis-assembly. A lot of prep work had to be done before hand...

In the meantime... Update 8/7/2024...



This video is an introduction to Duramax 6600 diesel service - and is the first in a series that will eventually show how to do what's necessary to complete a fuel injector replacement, cylinder head gasket replacement, water pump replacement and much more. But first, let's talk about what tools, tips and supplies you'll need to do the work in the best way possible.

If you're interested in learning more about Duramax 6600 service and repair, then the introductory YouTube video shown here would be the best place to begin. We've helped thousands of Duramax owners with their own service work through the years. We can help you too.

Can't wait for the video series to be complete? Would you rather have a complete printed Duramax Diesel Service Guide now?
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Lastly... The most recent video in this Service Guide video series has been posted near the end of this thread titled: No Fail - LB7 Duramax 6600 Injector Replacement. Have a look!

[Robyn]

Anxiously await lottssa pics

[Yukon6.2]

Watching as well i think the same job is in my future on my 2001 Tow truck.
Getting a hard rad hose,and losing fluid,smoke on starts

[a5150nut]

Will there be Pop Corn provided?

[Robyn]

BYOPC....
Shop towels advised.....Coveralls mandatory dress code.....yeah buddy

[More Power]

I'm looking at 2 possibilities, as of right now, for why I was seeing excessive pressure in the cooling system. By the way... there are patches of soot visible inside the coolant surge tank, which is a dead give-away.

The 2 possibilities...

#1- The No. 2 injector failed at about 120,000 miles (I identified it as having a way out of range fuel rate), which produced a "chugging" while the engine idled, like at a stoplight. I suspect that may have stressed the head gasket surrounding that cylinder - maybe.

#2- The excessive pressure in the cooling system was identified not long after an injector replacement (see #1). My GM Duramax mechanic/enthusiast friend seems to think the problem will be identified as a cup seal leak. He's seen enough LB7 cup seal leaks in his day (that follow an injector replacement) that he developed his own procedure to prevent them from happening. If my truck's problem is due to a cup seal... then it may have been a byproduct of risky/lazy injector replacement (meaning it was an independent shop's fault... ). Unfortunately, without taking it apart there's no way to tell if the excessive pressure is due to a bad gasket or a cup seal leak.

Another "by the way".... according to my mechanic buddy, the design of the Duramax head gasket produces a more likely problem at the #2 and #7 cylinder. If the head gasket were to fail... and that's not injector or cup related, the problem always winds up being associated with #2 or #7.

Have a look near the end of the following story on water pump replacement to learn more about head gasket failures*.... (LB7 cup seal problems). https://www.thedieselpage.com/durama...xwaterpump.htm

[Robyn]

Dig into it Jim
Gonna be interesting to see what ya find...

[More Power]

Here's a shot of the engine bay as it exists this morning (June 2, 2021). Getting closer... I need to unbolt the exhaust up-pipe from the exhaust manifold and remove the steel fuel lines. There's still a fair amount of electrical and plumbing to get the left side clear enough to look like this side.

I know there's a grounding strap on the back of the driver's side head (left side) that'll need to be unbolted. And, I think I just need to remove the three bolts at the bottom of each exhaust up-pipe to then free the heads... If I'm missing something, let me know. The book says the turbo needs to be removed to do a head R&R, but it looks like I can get the intake Y-pipe unbolted without removing the turbo. Just need to remove the turbo compressor inlet elbow to allow access to the intake bolts... I think.

Getting the electrical connectors disconnected up to this point took quite some time... There are many different types used here, and each has its own enigmatic snap-lock design (plus needing to be very careful due to 20 year old hardened/fragile plastic). You can see the soot in the plastic coolant surge tank...

[Kennedy]

We've done them in chassis I believe one time. Then started removing engine from chassis altogether. Easier to work on this way. Most lift the cab, and we always thought about it, but the risk of doing any paint and body damage...

Use a 10 mm ujoint socket for the turbo inlet bolts. The ones that I have are Snap on and have a very shallow socket.

ANY signs of rust on the injector inlet bowls or supply lines I would replace with new, in fact a set of SAC 00 injectors with new lines would be mandatory on my list. Hazing at idle shortly down the road will tend to break your spirit and all LB7 VCO seem sto do this. Some sooner than others.

[Robyn]

I am with John

I would clear off the crap on top and then yank the engine out.

One little issue in a hard to reach spot can lead to a redo.....and that stuff sucks.

Take your time and yanking the engine will not be all that bad.

THEN... you can walk up and get quite intimate with the old girl....
And if there are any other things that show up....they can be dealt with easily.

PLUS....While the engine is out...you can muck out the engine bay and make it all spiffy.....

[More Power]

We've done them in chassis I believe one time. Then started removing engine from chassis altogether. Easier to work on this way. Most lift the cab, and we always thought about it, but the risk of doing any paint and body damage...

Use a 10 mm ujoint socket for the turbo inlet bolts. The ones that I have are Snap on and have a very shallow socket.

ANY signs of rust on the injector inlet bowls or supply lines I would replace with new, in fact a set of SAC 00 injectors with new lines would be mandatory on my list. Hazing at idle shortly down the road will tend to break your spirit and all LB7 VCO seem sto do this. Some sooner than others.

Thanks John.

The injectors in the engine now only have about 20k on them. I had planned on having them cleaned/checked/tested before they went back in. But, I hear you on the "spirit" point... It's a lot of work to complete a project like this, to then have an injector issue soon/right after... I'll think about it...

Do you agree that the bottom 3 bolts on the exhaust up-pipes will free the heads from the exhaust system? Or, are there any bolts on the back side of the heads that secure the heat shields?

The GM mechanic I mentioned earlier told me that they lift the cabs too, but I was against it for of a variety of reasons - including damage to the cab, and then having persistent gremlins move in (with electrical, A/C, brakes, Allison shift cable, steering shaft, etc.). He then said his next option would be to pull the engine. Working mostly alone and without a vehicle lift, I pulled each inner fender wheelhouse and front tire/wheels, then lowered the front of the truck about 5-6 inches onto jackstands. Using plywood, I then made a 6" high x 24" wide x 48" long platform to stand on while leaning over the rad area. I can still pull the engine if it comes to that.

[More Power]

Had to buy a few more tools... i.e. a short 1/2" drive 12mm 12-point socket, a 10" long 12mm 12-point box wrench (need the leverage), 19mm flare nut wrench for the steel injector hard lines (although I used a 3/4" crow's foot, which worked perfectly), a set of 1/4", 3/8" and 1/2" drive adapters for my battery powered drill/driver, a set of metric Allen ball drivers and a couple misc tools to help out. Then, I removed the passenger side exhaust manifold and glow plugs. Up next is the driver's side exhaust manifold/glow plugs. I've heard that it's easier for one person to get a head up and out of the engine bay if the exhaust manifold has been removed. Gotta be careful not to ding the aluminum deck surface of the head.

Advice from John and others I trust say the ARP studs are the better choice over the factory TTY head bolts. So... we'll go with that. More later...

Update: 5/30/2024



This image shows the worst area of the worst head gasket. This is the block deck side of cylinder #2 (front-most cylinder on the driver's side). To recap, the engine had 140,000 miles on it at the time of the head gasket replacement in June of 2021, and the truck had endured 20 Montana winters. The head gasket leak began in about 2016 with the truck having ~120,000 miles on the odometer. I'd been living with this chronic, though slight, cooling system over-pressure problem for about 5 years. This made the truck unusable for anything but local driving all during that time.

It's hard to know how many cold starts occurred from when the truck was new to June of 2021, but it is my contention that over 15-20 years, the coefficient of expansion differential between the aluminum heads and the cast-iron block may have produced some scrubbing that contributed to a reduction in sealing ability of the head gasket, This eventually resulted in a combustion pressure leak into the cooling system -which was the reason for this head gasket replacement... The head gaskets simply wore out. This is why the service manual calls for a final finish of 600-grit wet/dry paper used with a light oil. A rougher texture on the deck surfaces, using some other method, will shorten the life of these gaskets.

I've had nearly 3 years to think about all this as of May 2024, and that's still my best guess as to the cause of the head gasket failure discussed here. There has been no excessive pressure buildup in the cooling system since the service. It's such a relief having the truck reliable again... TDP

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Thank you!

[Robyn]

Hang in there Jim......It will get easier the more stuff ya get off of the beast.....

[Dr. Lee]

This will give you a real workout, Jim. If I were closer to Montana I would be there to help you. If you do pull the engine out, you can do everything necessary to have it run another 20 years, and by then you might be ready for something different, like the diesel El Camino you have always wanted.

[DmaxMaverick]

The head and gasket look to be unremarkable. Really good for a 20 year old, actually. Just an observation.

80/120 grit on an aluminum head? I can see Scotch-Brite or 600 as reasonable, and what I might use. Anyone who'd suggest 80 grit gets no more of my attention. I doubt you could fix that with a mill.

[convert2diesel]

When re-doing the heads on a 6 liter gasser (aluminum heads) the FSM wants the surface to be "R15". When I got them back from the machine shop, you could almost see your face in the surface. In other words, check the FSM for surface requirements. Just a thought.

Bill

[DmaxMaverick]

According to (the latest bulletin regarding head/gasket prep and install):

Bulletin No.: 06-06-01-006C


Date: October 30, 2009


Subject: Information on 6.6L LBZ, LB7, LLY Duramax(R) Diesel Engine Cylinder Head Gasket Design Change - New Head Gasket Part Numbers and Head Bolt Torque Specifications


Models:
2001-2006 Chevrolet Silverado
2003-2006 Chevrolet Kodiak C4500/5500 Series
2006 Chevrolet Express
2001-2006 GMC Sierra
2003-2006 GMC TopKick C4500/5500 Series
2006 GMC Savana
with 6.6L Duramax(R) Diesel Engine (VINs D, 1, 2 - RPOs LBZ, LB7, LLY)

[snip]

Special Cleaning Requirements
For 2001-2006 vehicles produced with the first generation head gasket, special attention must be given to the cleaning of the engine block and cylinder head surfaces when servicing with a second generation gasket. The crimped areas (1) on the first generation gasket may, over time, allow corrosion buildup where they contact the block and cylinder head surfaces. The second generation gasket has raised ribs that seal at these crimped areas (1). A special cleaning procedure is required to ensure proper sealing.


Cleaning Procedure

1.	Remove the old head gasket using service manual procedures. Save the gasket for reference until the repair is completed.
2.	Place clean rags in the cylinder bores and pushrod openings in order to keep out debris.
3.	Use the J-28410 or equivalent to carefully clean the gasket sealing surface of large sealing or corrosion matter. When scraping, take care not to scratch or gouge the metal surfaces. Do not push the debris into oil, coolant, and combustion openings or bolt holes.
4.	Inspect the gasket sealing surfaces for corrosion, especially in the areas that were in contact with the crimped tabs of the first generation head gasket. If corrosion is present, continue with the rest of the steps in this procedure for proper cleaning. If the sealing surface is sufficiently clean and smooth, use the revised torque specification listed towards the end of this bulletin and continue with published service manual procedures to complete the repair.
5.	For surfaces that have corrosion or pitting, wrap a piece of flat steel (4"x 2" or larger) with 600 grit wet grade sand paper. Using Moisture Displacing Lubricant, P/N 88862629 (in Canada, use 89020803) or equivalent, wet sand the block surface to remove any remaining gasket material or corrosion. Do not use any paper coarser than 600 grit. Notice - Do not use any power type sanding devices. - Do not use a wire brush or wheel to clean gasket surfaces. - Do not use chemical cleaning agents on gasket surfaces.
6.	Take care to keep the sanding block parallel to the block surface and evenly sand the sealing surface. Some areas of corrosion will still show a stain. Do not attempt to wet sand these areas down to a shiny metal surface.
7.	Change the sanding paper when it becomes clogged. Carefully and frequently wipe the surface, using a clean cloth each time, to prevent sanding debris from building up and contaminating the oil and coolant cavities.
8.	Clean the bolt threads and holes and remove the rags from the bore cavities and pushrod openings.
9.	Repeat the above cleaning procedure on the cylinder head gasket surface.
10.	Clean the engine block and cylinder head gasket surfaces with Brake Parts Cleaner, P/N 88862650 (in Canada, use 88901247) or equivalent, to remove any traces of oil or debris.
11.	Using the revised head bolt torque specification below, reassemble the engine with NEW M12 cylinder head bolts according to service manual procedures.

Also:

Bulletin No.: 07-06-01-009A
Date: November 02, 2009

Addresses head gasket thickness identification, Gen 1 crimped gaskets vs. Gen 2 riveted gaskets, and revised head bolt torque and angle procedure. DO NOT use the original Gen 1 head bolt torque procedure with Gen 2 riveted gaskets. Definitely worth a read.

RTFM (note to self)

[Robyn]

I can't imagine using 80 grit.....omg...

[DmaxMaverick]

Thanks Greg... does the info you have list the new torque specs - i.e. "Using the revised head bolt torque specification below..."

It does, in the 06-06-01-006C bulletin. I'll send the PDF to your email. The bolt torque pattern isn't specified, but it's the same as original.

[More Power]

Thanks Greg,
The original gaskets identified in the TSB with arrows ("showing the crimped construction") did produce a buildup of rust on the block deck at each of those locations pointed to. Those small areas of rust build-up need to be removed, probably by first carefully scraping them down to block deck level.

Once I'm close to the end I'll make a list of the special and common tools that were either necessary or made the job easier. I'll also have some tips that'll make it easier, safer and produce a better result. I'd loan them all to you, but I have yet another LB7 to do once this one is back on the road. I'm sure it's punishment for something...