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Thread: The ol' Tahoe is down for the count - coolant in cylinder(s)

  1. #1
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    Unhappy The ol' Tahoe is down for the count - coolant in cylinder(s)

    After 376K faithful miles, the 6.5L in my Tahoe has finally had a major issue. Without any warning, she started blowing a lot of sweet-smelling steam out the tailpipe, and coolant is getting in the cylinder(s) causing it to hyrdolock after shutting it off.

    Everything was perfectly normal this evening, and then I stopped for fuel. Upon filling up and attempting to restart the engine, the starter cranked her over for a second and then stopped cranking. I thought it was odd, but figured it was just the starter getting old. I cranked her again, and this time the engine started, but started knocking loudly for a few seconds. That was really odd. She started running normally, so I pulled away from the fuel pumps, looked in my mirror, and saw a huge cloud of smoke. I pulled over and got out, but by the time I got to the tailpipe, it had cleared up. I drove on home (about 4 miles), and then she was smoking again; actually, it was steam. I shut her down, checked a few items, didn't notice anything out of the ordinary, and then cranked her up again. Once again, the starter stopped cranking after a second while making a weird noise. That's when I realized something was preventing the engine from turning over. I tried again, she started up, started shaking and missing, and blowing a LOT more steam!

    Here's a video right after I got home:

    https://www.youtube.com/watch?v=ExXS6BNtEVM

    After this video was taken, it started running horribly and smoking/steaming a lot more. In fact, by the time I drove it over to my shop a hundred yards away, I was wondering if it was going to stay running.

    It takes less than a minute after shutting down the engine for the cylinder(s) to get enough coolant in there to hydrolock the engine.

    My plan is to pull the glow plugs and then turn the engine over. That should pinpoint which cylinder(s) are getting coolant in them.

    What do you think? Blown head gasket? Cracked head? Cracked block? At this moment, there is no coolant in the oil. I released the pressure on the coolant tank, but haven't been able to run the engine to see if there was any noticeable exhaust in the cooling system.

    *sigh*

    Casey
    1995 K1500 Tahoe 2 door, 6.5LTD, NP241, 4L80E, 3.42's, 285/75R16 BFG K02's; Kennedy OPS harness, gauges, Quick Heat plugs, and TD-Max chip; Dtech FSD on FSD Cooler; vacuum pump deleted, Turbo Master, 3.5" Kennedy exhaust, F code intake, '97 air box; dual t/stats, HO water pump, Champion radiator; Racor fuel filter; 376K miles - blew head gasket!

  2. #2
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    Down for the count? Don't give up so easy. Most likely just a head gasket. Spend a weekend getting a little more personal with it, and it'll be fine. I'd do whichever side is blown. If you have the time, do both. If it's more than that, cross that bridge when you come to it.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  3. #3
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    Quote Originally Posted by DmaxMaverick View Post
    Down for the count? Don't give up so easy. Most likely just a head gasket. Spend a weekend getting a little more personal with it, and it'll be fine. I'd do whichever side is blown. If you have the time, do both. If it's more than that, cross that bridge when you come to it.
    Thanks for the encouraging words, Greg! I'm not giving up, just a little sad since I don't have a lot of spare time right now. It will be a while before she's up and running.

    Casey
    1995 K1500 Tahoe 2 door, 6.5LTD, NP241, 4L80E, 3.42's, 285/75R16 BFG K02's; Kennedy OPS harness, gauges, Quick Heat plugs, and TD-Max chip; Dtech FSD on FSD Cooler; vacuum pump deleted, Turbo Master, 3.5" Kennedy exhaust, F code intake, '97 air box; dual t/stats, HO water pump, Champion radiator; Racor fuel filter; 376K miles - blew head gasket!

  4. #4
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    Yeah, ID the cylinder(s) causing the problem. No coolant in the oil is a good sign.
    The Constitution needs to be re-read, not re-written!

    If you can't handle Dr. Seuss, how will you handle real life?

    Current oil burners: MB GLK250 BlueTEC
    New ride: MB GLS450 - most stately
    Gone but not forgotten: '87 F350 7.3, '93 C2500 6.5, '95 K2500 6.5, '06 K2500HD 6.6, '90 MB 350SDL, Kubota 7510

  5. #5
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    Sorry to hear. I agree with the others - take a look and hope for the best!
    '94 GMC 6.5TD K1500 4L80E 2-Door Yukon SLE 221K
    '93 Chevrolet 6.5TD K2500HD NV4500 Std. Cab Longbed 187K
    '85 Toyota 22R RN60 4x4 Std. Cab Shortbed 178K (Currently retired for rebuild)
    Diesel Page Member #2423

  6. #6
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    If you can afford it, buy a beater for transportation that you can resell after for about the same money.
    Then you will not feel rushed to do the job required to make your Tahoe your reliable transportation again.
    90 Chev 3500 c/c 4x4,6.2na,400 auto,4:10 gears.DSG Timing gears,main girdle, isspro tach, pyro,boost,oil and trany temp.Dual Tstats, High volume peninsular pump,on shelf, Custom turbo and intercooler 85%complete. Change of plans for the dually, it's going to get a Cummins. Both trucks are Blue 90 4x4 crews

  7. #7
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    Quote Originally Posted by Yukon6.2 View Post
    If you can afford it, buy a beater for transportation that you can resell after for about the same money.
    Then you will not feel rushed to do the job required to make your Tahoe your reliable transportation again.
    That's actually a thought I had... the wife isn't too keen on the idea, though!

    Casey
    1995 K1500 Tahoe 2 door, 6.5LTD, NP241, 4L80E, 3.42's, 285/75R16 BFG K02's; Kennedy OPS harness, gauges, Quick Heat plugs, and TD-Max chip; Dtech FSD on FSD Cooler; vacuum pump deleted, Turbo Master, 3.5" Kennedy exhaust, F code intake, '97 air box; dual t/stats, HO water pump, Champion radiator; Racor fuel filter; 376K miles - blew head gasket!

  8. #8
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    Even beaters are commanding top dollar these days.... I just had to replace one of our daily drivers and it's a tough market out there. Most of the ones I was really interested in were sold before I could get there to look at them.
    Last edited by JohnC; 07-21-2021 at 14:54.
    The Constitution needs to be re-read, not re-written!

    If you can't handle Dr. Seuss, how will you handle real life?

    Current oil burners: MB GLK250 BlueTEC
    New ride: MB GLS450 - most stately
    Gone but not forgotten: '87 F350 7.3, '93 C2500 6.5, '95 K2500 6.5, '06 K2500HD 6.6, '90 MB 350SDL, Kubota 7510

  9. #9
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    Been through this game a few times.

    Personally I would just get the engine out of the rig......It's not that bad of a job to yank it out.

    Than you can get it apart fast and easy.
    Head gaskets as mentioned are the likely suspects......

    My bet would be one of the two front cylinders where the coolant lays right on the deck and over time causes the gaskets to corrode and finally fail.

    Both of mine had eroded the block deck enough that we had to machine off .015" from the decks and use the thicker Felpro gaskets.

    One thing....With the engine out you can wash the engine bay well and do a really spiffy job making it look all new again.......

    Just an FYI
    No doubt so antifreeze has gotten into the crankcase and the oil.....Glycol is tough on a lot of parts...
    Unless you are planning on replacing a lot of things......Maybe drain the coolant completely, drain the pan and get a fresh oil and filter....then run the engine long enough to purge out the crud.

    When I did mine I tossed the lifters in the trash....and with the rebuild it got new bearings anyway...

    Good luck....

    Waiting to see pics of job as it progresses
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
    (1) 2007 Chevy Avalanche
    THIS IS BOW TIE COUNTRY

  10. #10
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    I've been working sun up to sun down this week, so haven't had much time to diagnose anything, but a quick check of the oil level last night showed the oil level had doubled, and the coolant level had dropped. That's not good. Would a blown head gasket or cracked head allow that much coolant to get into the oil pan just from sitting overnight? I'm hoping it's not a cracked block.

    I will have time this weekend to tear into things and really find out.

    Casey
    1995 K1500 Tahoe 2 door, 6.5LTD, NP241, 4L80E, 3.42's, 285/75R16 BFG K02's; Kennedy OPS harness, gauges, Quick Heat plugs, and TD-Max chip; Dtech FSD on FSD Cooler; vacuum pump deleted, Turbo Master, 3.5" Kennedy exhaust, F code intake, '97 air box; dual t/stats, HO water pump, Champion radiator; Racor fuel filter; 376K miles - blew head gasket!

  11. #11
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    My Suburban blew the gasket on the front of number 2 cylinder (Where I was talking about) and it filled the engine chuck full of Glycol)

    The close proximity of coolant that just lays on the deck and eventually soaks into the gasket causes erosion of the fire ring area and over time the block deck etches out and leaves an actual little divit in the deck...

    Once this happens the gasket fails.

    With the amount of coolant we are talking....this is my best guess...

    When our Burb did it I hit the starter and the engine hydro locked and the starter fell off.

    Bolts broke...block was fine...lucky shot...

    Get it out and then you can do the post mortem easily..

    Myself I like to yank the turbo and manifolds off the engine as this makes getting the engine out easier.

    Get the RH front tire off and the rubber inner flap off....This gives gobs of room to get in and remove the exhaust manifolds, the turbo drain pipe, the starter electrical connections and the front starter support ....all this stuff with far less fight and busted knuckles.......

    Get the fuel manager off the rear of the engine to gain access to electrical plugs and the bell housing bolts.

    GET A 9/16" FLEX HEAD GEAR WRENCH.....TO DO THE UPPER TRANNY BOLTS.

    Your rig should have SAE bolts....96 and later used metric in this location.....

    A totally factory install has stud top bolts with lock nuts to secure the fuel feed and return pipe bracket to the top two bolts on the tranny.... (If the bolt comes loose while removing the nuts holding the fuel pipe brackets it can require grinding down an open end wrench to hold the bolt head at the block)

    This lash up with the fuel pipes is a POS and can be a PITA

    The other tranny bolts are easily accessed from under the rig while getting the bottom bell housing cover off....and the starter....


    Just an FYI
    My rig was down for some time while I did the rebuild....The Glycol had caused the turbo to stick.

    To stop this issue ....Flush the turbo oil passage out with solvent or gasoline...both the oil feed passage and the exhaust passage through the hot side.....Dry and then add oil to the oil feed line and store the turbo until you need it...

    Remember....the engine oil cooler is likely contaminated too......Remove the radiator (Usual thing when getting the engine out) flush the radiator and the oil cooler.

    I used GUNK foam engine cleaner in the oil cooler...then water to wash it out.

    Then solvent or gasoline to finish it off..
    Blow out the lines and let dry.

    I like to leave the AC system intact.....just tie off to the inner fender with bungy strap or ????

    Stick a piece of plywood or??? in the protect the condenser core.

    All the wiring is pretty much ...such the the plugs are not interchangeable.. Mark them if you wish....

    The oil cooler lines at the engine are a "Snap in lock type fitting" You can wrench the block fittings off and fight the lock rings later.

    Unless the oil lines are recently new....Replace these with either a new factory type or a set of braided type lines with JIC fittings.....

    These are not pleasant to replace with the engine in the truck.

    I usually unhook the oil lines at the radiator and leave them on the engine.....Install new on the engine and then it's easy to reconnect later.

    Fighting things is something I avoid at all cost....Because if it's a PITA to get to or work on....it just might leak or ????? later.

    The inner fender access point on the RH side will allow you very easy access to the glow plug tubes and wires and manifold bolts.

    Installing the manifolds after the engine is set makes life easy.

    Remove the lower RH motor mount from the frame pad before you lift.

    Easy to do and this allows the engine to be shifted slightly to the RH side and then barely off the frame and its out.

    Otherwise some rigs have settled enough (Body mount sag) the the rear of the engine will hit the firewall before the motor mounts clear the frame brackets.....and life gets ugly.

    Just reverse the procedure going back.

    Remove the six nuts on the converter to flex plate and shove the converter back into the tranny a bit....Good to go.

    Ply wood chunk across a floor jack under the tranny pan before you lift the engine..

    A couple long 3/8 bolts into a couple tranny bolt holes and stick a piece of 2 x 2 wood (Twig) across the fame and set the tranny down on them.

    All snug as a bug in a rug until its time to replace the engine.

    Now this is me (Very anal) I grab a box of Sandwich bags and "Tag and bag" all groups of bolts as I go and label them.

    This makes the return far easier and the right bolts go back where they came from.

    It is nice to be able grab a bag of bolts/nuts and have what you need for the area you are working on..

    Really a pain when you toss everything into a bucket and then try to sort it out weeks or months later.

    I put all my bags of bolts and such in a box in sort of the order I will need them going back.

    Bags and a sharpie pen.... yessssssssssss....

    I have done several of these rigs and done it with the tag and bag program ....never ended up short or long on parts.

    And things look like Ma General had it .

    TAG'EM AND BAGE'M ..

    Good luck......
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
    (1) 2007 Chevy Avalanche
    THIS IS BOW TIE COUNTRY

  12. #12
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    Thank you Robyn! I'm glad to hear it could still possibly be just a head gasket. Did you have the block decked to get rid of the erosion issue?

    I ditched the factory fuel manager several years ago in favor of a Racor fuel filter, and I replaced all the fuel hoses with aftermarket hoses. I cut the factory lines at the back of the block, so all that's left back there is a couple of short pieces bolted to the block, so I won't have to fight with all that. I also have steel-braided oil cooler lines installed already.

    Casey
    1995 K1500 Tahoe 2 door, 6.5LTD, NP241, 4L80E, 3.42's, 285/75R16 BFG K02's; Kennedy OPS harness, gauges, Quick Heat plugs, and TD-Max chip; Dtech FSD on FSD Cooler; vacuum pump deleted, Turbo Master, 3.5" Kennedy exhaust, F code intake, '97 air box; dual t/stats, HO water pump, Champion radiator; Racor fuel filter; 376K miles - blew head gasket!

  13. #13
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    Yes...I stripped the block down and sent it to the machine shop and we cut the decks.. .010" as recommended did not clean so we went to .015" and got clean metal.

    We did both sides the same to keep the compression ratio balanced

    Sadly the engine needs to come all the way down to bare bones, cam bearings and all oil passage plugs out....then hot tanked and then machined then rewashed ...

    Best plan IMHO is to yank the sucker out and then open it up and see wassssup. My bet is either cyls 1 or 2

    JUST A LITTLE HINT.

    I have no idea what you have been into...so..

    When removing the injector lines
    Mark the pairs as to 1-3...5-7 LH and 2-4...6-8 RH and keep them in pairs..connected with the factory clamps.

    Make a map of the DS4 rotor head connection as to where the lines all fit.

    There are two lines that can be swapped....They run like crap this way....Ask me how I know this....then ya have to rip it apart again. A crow foot and a 3/8 breaker bar work sweet to get at the pump lines.

    Take a real good look at the electrical harness that lays in the valley to connect to all the engine connections.

    These do get ragged after many years and miles.....Replacement with new may still be possible....IIRC the after market has these harnesses available.

    A pain to replace with the intake on......
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
    (1) 2007 Chevy Avalanche
    THIS IS BOW TIE COUNTRY

  14. #14
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    The best way to do it is certainly to pull the engine and strip it down. However, if time and resources are limited, I suggest not doing that, just yet. Identify which side is the trouble, strip the top/front of the engine down (remove accessories, turbo (if passenger side issue), intake, pumps, etc.), and remove that head. See what you have to deal with. Whatever you find on one side, will likely be similar on the other, so keep that in mind. If you need to pull the block, it's much easier with the heads out of the way. If the block deck is good (a coin toss), deal with the head (repair/replace/clean up) and reassemble with new gaskets/bolts. The engine is a high-miler, so pulling it should mean a full overhaul. If you aren't interested in that unless necessary at the moment, minimize the efforts and time. Definitely fully flush the fluid systems ASAP to eliminate the cross-contamination, and preserve them for duty when that time comes. Time is very important, as the glycol, water, and additives can damage bearings, lubricated friction surfaces and such in a short time. Make it a priority.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  15. #15
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    Quote Originally Posted by Robyn View Post
    I have no idea what you have been into...so..
    It's been about 15 years since I've done major engine work. Back then it was when I yanked my 6.2L out of my '81 C20 project to replace a bad lifter; the "Might as Wells" resulted in a fully customized 6.2L that was bored .040 over with custom, ceramic-coated lower-compression pistons, all new fuel delivery system, stud girdle, timing gears, etc, etc. But it's been a few days since I've done anything like that, so I sure do appreciate the tips!

    Casey

  16. #16
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    Quote Originally Posted by DmaxMaverick View Post
    Identify which side is the trouble, strip the top/front of the engine down (remove accessories, turbo (if passenger side issue), intake, pumps, etc.), and remove that head. See what you have to deal with.
    That is exactly my plan. I want to discover what the issue is, and THEN step back and form a game plan.

    Casey
    1995 K1500 Tahoe 2 door, 6.5LTD, NP241, 4L80E, 3.42's, 285/75R16 BFG K02's; Kennedy OPS harness, gauges, Quick Heat plugs, and TD-Max chip; Dtech FSD on FSD Cooler; vacuum pump deleted, Turbo Master, 3.5" Kennedy exhaust, F code intake, '97 air box; dual t/stats, HO water pump, Champion radiator; Racor fuel filter; 376K miles - blew head gasket!

  17. #17
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    Also....very important.....BE VERY SURE TO CHECK THE POSITION OF THE PISTONS WHEN AT TDC
    The pistons should be at DECK HEIGHT TO .005 PROTRUSION ABOVE THE DECK

    Most engines will be at deck height.

    If you end up cutting the decks you do not want to find out that they have already been cut before.

    BEEN THERE DONE THAT....UGLY...
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
    (1) 2007 Chevy Avalanche
    THIS IS BOW TIE COUNTRY

  18. #18
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    [QUOTE=Robyn;332102]Also....very important.....BE VERY SURE TO CHECK THE POSITION OF THE PISTONS WHEN AT TDC
    The pistons should be at DECK HEIGHT TO .005 PROTRUSION ABOVE THE DECK

    Most engines will be at deck height.
    When i pulled the heads on my first GM Diesel a 6.2 i found a piston that sat lower that the rest.
    The rod got bent at some point years befor i got it.The piston sat a bit lower than the rest.I changed the rod and cut the ridge from the cylinder.
    It ran for years with one hole that would smoke a bit at start.I always assumed it was the one that had the bent rod.

    If you end up cutting the decks you do not want to find out that they have already been cut before.
    90 Chev 3500 c/c 4x4,6.2na,400 auto,4:10 gears.DSG Timing gears,main girdle, isspro tach, pyro,boost,oil and trany temp.Dual Tstats, High volume peninsular pump,on shelf, Custom turbo and intercooler 85%complete. Change of plans for the dually, it's going to get a Cummins. Both trucks are Blue 90 4x4 crews

  19. #19
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    When ya get this old stuff apart you can uncover all sorts of mischief ......yeah buddy
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
    (1) 2007 Chevy Avalanche
    THIS IS BOW TIE COUNTRY

  20. #20
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    Default Update 7/25

    Update: Pulled all the glow plugs. On the passenger side, the first three cylinders were dry. The number 8 plug was wet, and when I removed the plug, coolant dribbled out of the hole. I then proceeded to the driver side, and the first two plugs were dry, number 5 was damp, and number 7 was really wet. In fact, when I pulled that plug, a lot of coolant came out, and continued to drip coolant for some time (even after draining and removing the radiator).


    Cylinder 8 glow plug removed:






    Cylinder 7 glow plug removed:










    This is the amount of coolant that drained out of cylinder 7 after removing the glow plug:









    I was confused to find coolant in both rear cylinders; I would have expected to find it one side of the engine, but not both; I started wondering if there was a block issue?



    I went ahead and proceeded with removing the driver's side head since cylinder 7 seemed to be in the worst shape:














    The head gasket on cylinder 7 was obviously blown out into the water jacket on the rear of the head:





    I can't hardly get my head into cylinder 7, but so far I don't see any cracks or catastrophic damage. In fact, I was shocked to see how clean the cylinders and pistons were! There's not even a ridge at the top of any of the cylinders.

    I have decided to go ahead and pull the engine the rest of the way out; at this point, the only thing left holding it into the vehicle are the motor mounts and the transmission. I might as well get it out on the stand where I can do a proper head gasket job. Also, the passenger side exhaust manifold bolts are in such poor shape, I'm not sure I can get the manifold out without a lot of cussing. It will be easier to pull the engine and work on the exhaust manifold then.

    At this point, assuming I don't find major block issues on the passenger side after pulling that head, my plan is to pull the oil pan, check a few bearings, and if all looks good in the bottom end, I will then throw in a new oil pump, rear main seal, and install new head gaskets. I might as well replace the injectors while it's easy to do, and perhaps upgrade the turbo to an HX35. I will also take the opportunity to replace the torque converter, since lately I've noticed it slipping when towing my camper. That is really as far as I want to go; I don't want to do a full rebuild if not needed.


    Casey
    1995 K1500 Tahoe 2 door, 6.5LTD, NP241, 4L80E, 3.42's, 285/75R16 BFG K02's; Kennedy OPS harness, gauges, Quick Heat plugs, and TD-Max chip; Dtech FSD on FSD Cooler; vacuum pump deleted, Turbo Master, 3.5" Kennedy exhaust, F code intake, '97 air box; dual t/stats, HO water pump, Champion radiator; Racor fuel filter; 376K miles - blew head gasket!

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