Head Gasket?

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Akkaid, Mar 3, 2021.

  1. Akkaid

    Akkaid Bobtail Member

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    Oct 26, 2017
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    Hey yall,

    '99 Pete with a 12.7 DDEC4, 390,000 on rebuild. Truck runs good, doesnt over heat, not losing coolant, oil consumption is so-so (got a cam shaft seal leak and a cracked filter housing, so yeah). I drained and replaced the coolant 'cause I dont like the green stuff. Lost track of how much coolant I added (5 kids) and thought I was done. Made a run, overheated a bit, hit 210, I backed off and hit the fan, everything was fine. Forgot I didnt fill coolant, so I added some and did the coke bottle test thinking I puked it all out. Had air from overflow hose. Did a block test to confirm, but couldnt get it to turn color past a blue-green. I scheduled shop time to do head gasket, but 2k miles later I got no coolant loss, no oil loss, no oil in coolant, no coolant in oil, no over heating, no power loss.

    Im now wondering if it could be something else. I figure I can warm up the engine, release pressure, run a few miles, dump the air tanks, remove air output from compressor and test for bubbles...Will that rule out compressor?

    Someone mentioned an injector could cause this too, but for the life of me I cant figure out how an injector could make bubbles...

    I replaced coolant cap, and I just noticed the cap is a 7 PSI, the service manual calls for a 9 PSI cap. 2 PSI isnt much, but it is 20% weaker than called for, could this be an issue?

    I sent my oil out to Blackstone for an expedited analysis. Im not here trying to grasp at non-head gasket straws, just want to troubleshoot every #### thing before next Tuesday. Ive had some issues with the air system before, but dont notice any leaks around the head. If you can think of anything, please holler.
     
    jamespmack Thanks this.
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  3. 062

    062 Road Train Member

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  4. jamespmack

    jamespmack Road Train Member

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    210 I wouldnt be concerned with. Having the right cap is very important. Could you bubbles simply been air trapped in the system. Maybe.

    Start with unhooked compressor discharge just so it doesn't build psi first. The block, or pinch off coolant lines to compressor.

    Kinda sounds like you don't have a problem. Some of the Low Nox programs don't even turn fan on till 217ish.
     
  5. 6cuda6

    6cuda6 Light Load Member

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    May have just had an air lock in the system someplace.
     
    Rideandrepair and jamespmack Thank this.
  6. Akkaid

    Akkaid Bobtail Member

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    Oct 26, 2017
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    Thanks yall, Im gonna wait for the oil analysis to make any repair decisions, Ill keep an eye on the temp, but she's runnin up Monteagle at 86k without breaking 200.

    Can someone spell out how to do the test 'around' the compressor, Im a details guy, and cant find the process in the service manual.
     
    Rideandrepair Thanks this.
  7. AModelCat

    AModelCat Road Train Member

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    You probably won't find that test in a manual. More of a common practice.

    An injector itself wouldn't pressurize the coolant but an injector cup likely could. You'd probably see coolant loss and would possibly hydraulic a cylinder after being shut down if it were bad enough.
     
  8. Hammer166

    Hammer166 Crusty Information Officer

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    Two ways to go about it. Easiest is to unhook the hot line so it won't build pressure.

    To absolutely remove it from the circuit, just pull the coolant lines off the compressor and plug them or hook them together.
     
    Rideandrepair Thanks this.
  9. Akkaid

    Akkaid Bobtail Member

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    Wouldnt that burn up the compressor?
     
    Rideandrepair and jamespmack Thank this.
  10. Hammer166

    Hammer166 Crusty Information Officer

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    Short term, no. You do it long enough to test if that's where your pressure is coming from.

    Back in the day, compressors weren't water cooled at all, just by the oil. Water cooling was added 20 some years ago for longevity. But I wouldn't run without the water for any length of time.
     
  11. BoxCarKidd

    BoxCarKidd Road Train Member

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    Telling your age friend.
     
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