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Thread: 7.8L isuzu diesel oil in coolant.

  1. #1
    Join Date
    Jan 2010
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    Default 7.8L isuzu diesel oil in coolant.

    2004 GMC 7Tf042. Isuzu 7.8L diesel engine. Oil in coolant. No coolant in oil. I'm a truck fleet mechanic and have three trucks with this problem. I have the engine oil cooler off and see no visible defects. If anyone has seen this problem and can lead me in a direction I would greatly appreciate it.

  2. #2
    Join Date
    Sep 2001
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    Ft. Wayne, In.
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    Default

    Sorry you haven't got any responses to your post yet Tom.
    I have a feeling the ones in the know must have been tied up this weekend. Give it a day or two more.
    Also, try emailing Jim ("More Power") directly.
    Good Luck!
    Dave
    Dave, N9LOV
    Member #242
    Dave's Diesels:
    Sold June, 07 '82 1/2 ton 4X4;340k miles
    '97 2 Dr Tahoe, Intercooled,
    Kennedy ECM, 4" Exhaust
    '02 GMC

  3. #3
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    Jan 2010
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    I know it's a hard one. Hopefully someone has seen this. Pressure tested oil cooler to 100 psi(ok). Pressure tested air compressor water jacket to 60 psi(ok). Tapped oil pan after it sat over weekend. No coolant visible.

  4. #4

    Default 7.8 Duramax Oil In Coolant

    IT'S LIKELY THE OIL INTER-COOLER / EGR MANIFOLD ASSEMBLY BOLTED ON THE SIDE OF THE BLOCK UNDERNEATH THE INTAKE MANIFOLD. I HAVE FACTORY SHOP MANUAL & IT DOES NOT ACKNOWLEDGE THE EXISTENCE OF THIS SIGNIFICANT PART - NOT EVEN IN THE ENG. TEAR DOWN SECTIONS. THE MOST LIKELY PART OF THE ASSEMBLY THAT IS LEAKING IS WHERE THE INTERNAL OIL RADIATOR LIKE SUB ASSEMBLY BOLTS TO THE HOUSING - THERE ARE 2 THERMOSTAT SIZED & SHAPED COPPER GASKETS THAT WILL LIKELY BE THE CULPRITS. SUGGEST PRESSURE TESTING THE INTER-COOLER ASSEMBLED & BROKEN DOWN (OIL RADIATOR REMOVED & ISOLATED). THE OIL RADIATOR HAS STUDS THAT PROTRUDE OUTWARDS TO EXTERIOR OF THE HOUSING IN WHICH YOU CAN SEE THE 14 MM NUTS- 2 TO THE LEFT OF CENTER & 2 TO THE RIGHT OF CENTER - THAT RETAIN IT. THE REST OF THE BOLTS ON THE EXTERIOR OF THE INTER-COOLER ARE THE HOUSING'S MOUNTING HARDWARE. RECOMMEND TO LEAVE 14MM NUTS INTACT UNTIL REMOVAL OF HOUSING SO AS TO BE ABLE TO INSPECT COPPER GASKET MATING AREA B4 DIS-ASSEMBLY. CHEV DEALER PARTS DEPT. DOES HAVE SCHEMATICS OF THIS ASSEMBLY & HAPPILY PRINTED THEM OUT 4 ME. ASSEMBLY COSTS $691.00 - BUT IT IS LIKELY YOU WILL ONLY NEED GASKETS & O-RINGS TO SOLVE PROBLEM. HAVE PICS OF ASSEMBLY REMOVAL STEPS ( DID NOT HAVE TO REMOVE FUEL PUMP) & BROKEN DOWN INTER-COOLER ASSEMBLY IF NECC. I'LL CHECK THIS POST EVERY FEW DAYS TO SEE IF YOU WANT ANY FURTHER INFO. 2004 CHEV T7500
    Last edited by catwalkerr; 02-05-2010 at 14:10. Reason: TYPOS & TECH CORRECTION

  5. #5
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    Jan 2010
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    Sorry I haven't checked in latetly. My engine seems to be an early one. No EGR and no water cooled turbo. I did remove the engine oil cooler and housing. I made some plates to pressure test the cooler and it tested good. The o rings between the core and it's housing were flat and pitted slightly, but not torn. I have looked at some of the other trucks with this problem and some have EGR and water cooled turbo some don't. I appreciate the input. I looked at the truck tonight for the first time since I had the cooler out and it looks pretty good, but has only gone 400 miles in the last month. Again, I really appreciate the input and if you have any other ideas I would like to hear them. I'll check this post more frequently and I'll post in another 30 days and let you know if oil came back.

  6. #6
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    Jan 2010
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    It's been 3 1/2 months and I think it is good to go. If the oil returns in the future I'll repost.

  7. #7
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    Glad the problem hasn't returned. I used to have an excellent contact with an Isuzu rep here in the US who worked with me on a number of writing projects since the Duramax was introduced, but he moved on a while back. That said, I would recommend contacting Isuzu (both US & Japan) through their web sites if you have a future problem that can't be solved locally. I've shaken hands with a number of top tier Isuzu people, and it's been my experience that Isuzu is very helpful and want owners to be satisfied with their engines.

    Jim

  8. #8
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    Jan 2010
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    Default Starting second truck

    Started on the second truck with oil in the coolant. this truck has an e.g.r. cooler. I contacted the local dealer for gaskets to mount the e.g.r. cooler to the housing. They are telling me you cannot buy the gaskets seperately, you have to buy the entire assembly. Does anyone have a parts breakdown or part number for the gaskets? 2004 GMC T7500 7.8L Isuzu diesel.

  9. #9
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    Jan 2010
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    Oil is back in coolant. If I ever figure out where it is coming from I'll post the solution. The second job was cancelled and the truck went to auction.

  10. #10

    Default Oil in Rad

    Tom sorry to hear about your oil problem i see it's been awhile since your last post. Not sure if you got it figured out yet or not. If it takes a while for the oil to show up in your Rad it probably your injector cups. What happens is oil sit on top of the head around the cup and as the coolant system cools it make a vacuum pulling oil into the coolant. Isuzu had a problem with that era engine because they only had one O ring on the cup. They updated the heads and cups i believe in 2006. I hope this helps. Not a a real big job to do if you have the tools

  11. #11
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    Well, I had a long conversation with the GMC dealer and they claim they called tech support. They recomended replacing the engine oil cooler. I sent the truck to them and they replaced the oil cooler and flushed the cooling system and replaced all the hoses because of swelling. 2 months later and the oil is back. I appreciate the feed back about the injector cups. When the hoses swell up and start leaking again, I'll get the cups replaced.

  12. #12
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    Thanks to DieselTech04401. The injector tubes fixed the oil in coolant problem.

  13. #13
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    Jan 2001
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    A little simple Green in the cooling system is a great way to clean that part of this up. Seen the CAT mechanics do this quite a few times.
    "The Constitution is not an instrument for the government to restrain the people, it is an instrument for the people to restrain the government."
    -Patrick Henry


    A5150nut
    2006 K3500 D/A
    94 6.5 4x4 5spd Sold

  14. #14
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    Default oil in coolant

    Tom 2010, a update on the oil in the coolant, is it still doing good?

  15. #15
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    As of 5/17/13 the oil has not reappeared.

  16. #16
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    Arrow

    Thanks for the update. Good luck!
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  17. #17
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    Sep 2015
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    Usa
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    Default 2000 Isuzu FTR oil in coolant

    Hello Tom
    I just bought the used truck 2000 Isuzu FTR a month ago and now found out that I have oil in coolant. I noticed that you have this problem before. Can you be able to help ? I am not a mechanic but I am handy man, with your help I hope I can be able to fix it. I just flush out all the coolant and clean all the pipe and radiator and did the oil change as well. Please show me how to fix the leaking?

  18. #18
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    Default 2000 Isuzu oil in coolant

    Hello DieselTech04401

    I have 2000 Isuzu FTR truck. Had oil in coolant, can you show me where the injector cups locate?

  19. #19
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    Abui you might try looking here specializedhauler.net/archive/index.php/t-2423.html
    Last edited by DmaxMaverick; 09-27-2015 at 21:19. Reason: Corrected link
    "The Constitution is not an instrument for the government to restrain the people, it is an instrument for the people to restrain the government."
    -Patrick Henry


    A5150nut
    2006 K3500 D/A
    94 6.5 4x4 5spd Sold

  20. #20
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    The site doesn't work.

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