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Thread: Duramax Head Gasket Replacement

  1. #41
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    Thats what they sell masking tape and sharpies for.

    Looking good.

    Bill
    91 Buick Roadmaster/Avant 6.2 NA conversion (gone but not forgotten)
    94 Cadillac Fleetwood (sold)
    08 Aerolight 23TT
    06 Vortec Max Silverado CC SB (sold)
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  2. #42
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    Yup.......Been there done that trip.......

    Butttttttttttttttt.....Most electrical connectors are item/location specific and will only go one place.
    (1) 1995 Suburban 2500 4x4
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  3. #43
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    Thumbs up

    It lives!

    Started it for the first time this morning. Checked for leaks after the first two non-firing cranking sessions. Found a pretty significant fuel leak on the forward end of the right fuel rail. Seems I forgot to tighten the fuel line nut (pointed to in photo below) that feeds the rail... Only needed to remove the alternator and AC compressor (to get the alt off). Luckily, I could get my 3/4" claw-foot and an extension to work with my tq wrench to reach under the wiring bundle in that area. That fitting is tq'ed to 30 ft-lbs. I think it's leak free now.



    No abnormal pressure buildup in the cooling system, which is why all this was done in the first place. Starts and runs really well. Drove it a few miles to burp the cooling system. No SES lamp or trouble codes. Sounds a little different than before.

    When re-installing all of the coolant-related parts on top of the engine, I noticed that most of the gaskets and o-rings had been leaking/oozing a little over time. I suspect that the cooling system over-pressure the engine had been having over a long time worked on the gaskets/o-rings too. I replaced all of those gaskets/seals/o-rings and installed new thermostats. The rubber gaskets on the t-stats had been leaking a little too, and they weren't properly regulating engine temperature - ran a little on the cool side.

    Once the engine cools overnight, I'll change the engine oil and filter, then re-install the wheelhouse liners. Hopefully that's it. "Only" about 80 actual hours start to finish, not counting the ~400 mile round trip to get the heads resurfaced. No broken parts, no lost (or "left over") bolts/hardware, no broken electrical connectors, no scratches on the truck, just a few scraped knuckles, got a better result for far less money... New SAC00 injectors, new updated "C" grade head gaskets, new injector hard lines and ARP studs, plus some new tools (including two small torque wrenches) for something over $4K. I'll have a more accurate accounting when I go through the pile of receipts. This job would have cost $10k if you'd hired it done...
    Last edited by More Power; 08-20-2021 at 08:54.

  4. #44
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    Quote Originally Posted by convert2diesel View Post
    Thats what they sell masking tape and sharpies for.

    Looking good.

    Bill
    Thanks Bill,

    Mostly kidding about the electrical connector puzzle...

    Although, it took me a while to figure out one connector on the driver's side. The answer came when I remembered that it was for the oil pressure sender connection to the engine harness. On the passenger side, I had this important-looking connector on the harness that had no mate on the engine, then I remembered it was for the MAF sensor on the airbox (which was sitting on the parts table). And lastly, the glow plug controller module has 4 connections. I didn't do a good job documenting the wiring, so I had to dig through my photo archive to find a photo of a wired GPCM. The best photo I had only showed a part of the module, but after some head scratching it was enough. Every other electrical connector was, as Robyn said, pretty much self evident - there are so many of them...

  5. #45
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    Good to hear that things went reasonably well....

    The first start up after a major tear down is always tedious and usually bends the nerves a bit.
    Looking forward to hearing the results of the road test.....
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
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    THIS IS BOW TIE COUNTRY

  6. #46
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    Congratulations Jim!
    Glad to see you got it up and running again. 80 hours isn't so bad for a guy who doesn't do it for a living....
    Way to go!
    Dave
    Dave, N9LOV
    Member #242
    Dave's Diesels:
    Sold June, 07 '82 1/2 ton 4X4;340k miles
    '97 2 Dr Tahoe, Intercooled,
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  7. #47
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    Quote Originally Posted by DieselDavy View Post
    Congratulations Jim!
    Glad to see you got it up and running again. 80 hours isn't so bad for a guy who doesn't do it for a living....
    Way to go!
    Dave
    Thanks Dave. Not as young as I used to be either... 36 stud nuts each torqued in sequence at 30, 42, 84 and 125 ft-lbs while sitting on the rad core support was a high point...

  8. #48
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  9. #49
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    Take 2?
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  10. #50
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    Quote Originally Posted by DmaxMaverick View Post
    Take 2?
    There was once an "incident" with nitrous... producing a nagging cooling system overpressure. I suspect a couple of the head bolts may have yielded a bit. The first head will come off later today or tomorrow, depending on how much time I get to work on it. Working on the engine is generally easier in Lil Red than it was in the GMC - the truck is lower, and there's more room in certain areas (rear of the driver's side head). Plus Lil Red has a lot fewer miles (about 10k), has never been apart before and has never seen road de-icer.
    Last edited by More Power; 10-06-2021 at 13:07.

  11. #51
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    Quote Originally Posted by More Power View Post
    There was once an "incident" with nitrous... producing a nagging cooling system overpressure, that I suspect may have caused a couple head bolts to yield a bit. The first head will come off later today or tomorrow, depending on how much time I get to work on it. Working on the engine is generally easier in Lil Red than it was in the GMC - the truck is lower, and there's more room in certain areas (rear of the driver's side head). Plus Lil Red has a lot fewer miles (about 10k), has never been apart before and has never seen road de-icer.
    I was a little more cautious with the nitrous and propane in my 6.5L. You gotta keep Lil Red in top-notch shape, you have LOTS of sweat equity and brain-power equity invested in her.
    Dr. Lee

    1984 C-10, custom 6.5L SAA, custom 700R4, Gone but NOT FORGOTTEN

  12. #52
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    Sounds good.....

    Be interesting to see what actually happened...and why the pressure issue....
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  13. #53
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    Quote Originally Posted by Robyn View Post
    Sounds good.....

    Be interesting to see what actually happened...and why the pressure issue....
    Robyn,

    My thoughts about the causes of over-pressure problems are evolving. My thinking at the present time include:

    1- The head gaskets simply wear out over years of use due to the friction caused by differences in the coefficient of expansion rates between aluminum and cast-iron. I suspect there's a direct correlation between thermal cycles and head gasket life (in the case of my GMC - 15+ years and 140,000 miles), at least with the original crimped head gaskets.

    2- Head bolt(s) yield for whatever reason (especially when beyond stock power/boost levels), which reduces the clamping load - resulting in combustion pressure leaks. With Lil Red, there's a direct connection in time between a nitrous backfire at the track and the first appearance of the cooling system overpressure... What's interesting is that GM reduced the head bolt torque angle settings (reduced the torque) of the same TTY head bolts when installing the newest riveted head gaskets. Perhaps the earlier/original crimped tabs were interfering with head bolt clamping force.

    3- The original head gaskets used crimped tabs at various places around the perimeter of each gasket. These crimped tabs were what kept the multi-layer gaskets locked together. The tabs are thicker than the surrounding gasket and are located between the head/block surfaces - making it harder for the head bolts to effectively clamp/seal the gasket. You can see what effect this has on the gasket and where most of the questionable sealing occurs. The new riveted design has the riveted areas outside the head/block mating surfaces, so they don't interfere with the effectiveness of the head bolts to maintain clamping load over time.
    Last edited by More Power; 09-21-2022 at 10:11.

  14. #54
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    I watched an ARP video a while back where they discussed the "elastic" clamping load supplied by properly installed and torqued Series-2000 head studs produced for the Duramax. I like it that the ~$650 head studs have some elasticity designed-in.

    However, we know that GM is still using TTY bolts in the newest L5P Duramax, which is rated for 445 hp / 910 lb-ft - and rated for up to a 35,000-lb GCVWR.

    I interviewed the "Duramax Power Tour" team in 2000, who drove an LB7 equipped 3500-series truck towing a 20,000-lb event trailer. I rode in that truck as they wailed on it, on the I-90 continental divide pass just east of Butte, Montana. I asked them if they drove it like that all the time. I was told yes... They put in excess of 20,000 miles on that truck - hammer down all the time. I can also point to a 750,000-mile LLY Duramax used to commercial tow RV trailers all over North America, that I wrote about a few years ago. GM could acquire head studs equal to those offered by ARP (maybe even contract with them to provide) if they felt it was necessary.

    I have a couple of debate points about studs that are hard to answer and difficult to challenge. 1- The aftermarket pushes anything that they can sell - ("while you're in there") type of stuff, including head studs. 2- Studs are simply easier to install than TTY bolts. You must mark the heads of each TTY bolt during the two angle tightening sequences or you'll mess up the installation. With studs, you only use a torque wrench. If you forget one or get out of sequence, it's really easy to check what the torque is for that stud. Personally, I think this is why many vendors/mechanics push studs (sell more expensive stuff and they are easier to install). Otherwise, they would/could point to actual durability tests involving direct comparisons between engines using head studs and TTY bolts (fleets would be the best source of information. Second best would be an accumulation of real-world reports from actual owners - like the story I did on the 751k mile LLY Duramax). For most, these head gaskets will wear out long before any real comparison can be done on the veracity of claims otherwise.

    I plan to measure the actual torque applied to these TTY bolts after completing the 2-step torque angle installation. We know that GM/DMAX reduced the final TTY head bolt torque angle setting when they introduced the new updated head gasket in 2007. I suspect this was to reduce the Brinelling of the head gasket fire-ring onto the aluminum heads. Knowing what the torque is for current ARP studs (125 ft-lbs), it'll be interesting to learn what the actual torque value is for the installed TTY bolts. The current TTY installation takes the TTY bolts from a static torque installation setting of 59 ft-lbs then adds two separate 60 degree rotations for a total 120 degrees. The original Duramax TTY bolts saw a 150 degree sweep after the 59 lb-ft static tq setting.
    Last edited by More Power; 07-22-2021 at 13:09.

  15. #55
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    I agree 100% on the TTY BOLTS.....A cheap easy fix instead of doing it the right way..

    You drive the rig with great care and NOT ...HAMMER DOWN .....The stock stuff will work.....

    Take it into the ozones a couple times.....Maybe it will survive....maybe not......

    A bolt that is already into it's elastic mode and then hit hard......all bets are off.

    TTY BOLTS are more like taffy.......

    A bolt that can stretch a little and come back will be far better than one that is into the"GOOOY PHASE" and then the extra hit simply stretches the bolts out waaaaay too far......."The bolts you found with less breakaway tension.

    I have found the same mentality with the big snow cat.....do it cheap and dirty.....Yeah...good for a while...but when it fails ...things get ugly..quick.....

    Are you going with studs on "Li'l Red" ?????
    (1) 1995 Suburban 2500 4x4
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  16. #56
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    A six and a half with REASONABLE power levels will do fine with TTY bolts.

    Try shoving big boost and a buttload of fuel into a 6-1/2 and it will suffer....

    I tried a set of MLS gaskets on a 6.5.....NOT ENOUGH HEAD BOLTS IF USING TTY..

    ARP studs may have worked better.......

    The factory stuff is always right on the ragged edge.....You always need more when you plan on flogging it hard.....
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
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  17. #57
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    Post "As long as we're in there..."

    Quote Originally Posted by Robyn View Post
    A six and a half with REASONABLE power levels will do fine with TTY bolts.

    Try shoving big boost and a buttload of fuel into a 6-1/2 and it will suffer....

    I tried a set of MLS gaskets on a 6.5.....NOT ENOUGH HEAD BOLTS IF USING TTY..

    ARP studs may have worked better.......

    The factory stuff is always right on the ragged edge.....You always need more when you plan on flogging it hard.....
    If money is no object, we would all live life differently and make different decisions regarding diesel engine service. Fact is, the ARP head studs are $650 and the factory TTY bolts are about $100.

    Take an old truck to a diesel shop or dealership, and ask them to install a new head gasket kit ($400), ARP head studs ($650), new injectors ($2400), new injector hard lines ($650), new water pump ($125), new hoses and an endless list of "as long as we're in there" stuff, and of course at least $5k in labor - and you've made a bad decision regarding financial common sense - i.e. spending $10k+ on a truck that in even perfect condition is still only worth 10K. When faced with that reality, most thinkers will crush/part-out the truck and not spend a dime on it... We didn't even talk about brakes, ball joints, steering components, drivelines, tires, rust... and on and on and on...

    Meanwhile, our performance 6.5TD Project ran without a problem to 300,000 miles in 7 years using TTY head bolts (till we sold it), and my 2001 GMC ran to 140,000 miles using TTY head bolts - even with the poorly designed factory crimped-style head gaskets. I get where the ARP stud advocates are coming from. This is partly why I installed ARP studs in my own 2001 GMC LB7 head gasket repair. I spent extra on this truck only because I did the work (and because I needed to install the studs so I could photograph it and eventually write about it). It's just that at some point, all those faced with a significant repair on an older truck need to make a decision... Do you crush the truck or do what is necessary to save it without compromising basic service and dependability while not violating financial common sense? As part of an overall budget strategy, I think the lower cost TTY head bolts fit into that paradigm. And... Lil Red is getting TTY bolts.

    What would mean most to me regarding this studs/bolts debate is to study the actual service histories comparing engines built with studs/bolts along with a description of how the trucks were used, and then be able to discern some sort of recommendation from that. Right now, the stud advocates "say" they are better... We can read about tensile strength and a wide range of engineering theory, but what's that really mean in the real world to average truck owners?
    Last edited by More Power; 12-06-2021 at 13:46.

  18. #58
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    Pretty much spot on..
    Trying to do a "Budget" rebuild any more is a real challenge.

    I am trying to build a 406 Small block Chevy for the snow cat....

    Used Vortec heads in great shape (Zero cash outlay....Sold the short block to recover the total cost)
    400 block $150 plus $350 for machine work
    Pistons....New ebay score for $135
    Good used stock crank.....$125
    Still need the cam/lifters
    Timing gear/chain
    Gaskets
    Oil pump
    Fuel pump
    Push rods
    Have new high capacity pan $175
    Flex plate

    And on it goes.
    Have a fresh carburetor $127
    New exhaust manifolds $175 pair

    Intake manifold for Vortec heads to fit 4 barrel carb.....$100 plus

    No matter what it is....even when you do all the wrenching yourself.....$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$ $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$

    Adds up quick
    (1) 1995 Suburban 2500 4x4
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  19. #59
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    "new injectors ($2400)" Are you writing about a 6.5 GM diesel? That's $300 per new injector?

  20. #60
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    Quote Originally Posted by 56pan View Post
    "new injectors ($2400)" Are you writing about a 6.5 GM diesel? That's $300 per new injector?
    That price is for remanufactured Duramax LB7 injectors. "New" as in replacing what was originally there. Prices vary between vendors. You can buy suspect stuff off eBay for less or spend a lot more for newly manufactured Bosch injectors. The $2400 price is for reman from Kennedy. Injector prices for newer model Duramax engines are more.

    I had hoped back more than 15 years ago that injector prices would fall for the older model Duramax. I knew that as the truck's book value dropped, a critical point would eventually be reached where the cost to repair exceeded the "drop dead" percentage of 50% of vehicle value.

    There is light though... I'll need to spend some time investigating, but it is possible to do what was unthinkable just a few years ago and replace the wear items in these injectors using only basic tools and skills. This, I believe, will become a big factor in saving the older trucks.

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