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  #1  
Old 01-15-2010, 05:15 PM
Tom2010 Tom2010 is offline
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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.
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  #2  
Old 01-18-2010, 07:08 AM
DieselDavy DieselDavy is offline
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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
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  #3  
Old 01-18-2010, 12:14 PM
Tom2010 Tom2010 is offline
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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.
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  #4  
Old 02-05-2010, 01:36 PM
catwalkerr catwalkerr is offline
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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 02:10 PM. Reason: TYPOS & TECH CORRECTION
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  #5  
Old 02-22-2010, 07:32 PM
Tom2010 Tom2010 is offline
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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.
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  #6  
Old 05-03-2010, 06:00 PM
Tom2010 Tom2010 is offline
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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.
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  #7  
Old 05-04-2010, 11:36 AM
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More Power More Power is offline
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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
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  #8  
Old 05-27-2010, 08:19 AM
Tom2010 Tom2010 is offline
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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.
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  #9  
Old 10-19-2010, 04:54 PM
Tom2010 Tom2010 is offline
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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.
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  #10  
Old 02-17-2011, 07:01 PM
DieselTech04401 DieselTech04401 is offline
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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
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