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  1. #1

    Default So I found this horrible link regarding coolant loss without a leak...

    I cannot find anymore on this other than the linky right here

    http://www.agcoauto.com/content/news/p2_articleid/148

    Anyone have this happen to them? is this common knowledge here (but not to me?)

    thanks for the input.

    If your General Motors SUV or truck is losing coolant, with no visible signs of a leak, the source may shock you

    Worse, allowing the problem to go on may well mean a new engine.On several occasions General Motors vehicles, with the 5.3L and 4.8L engines have come to us because of a coolant leak. There is no outward signs of coolant leakage, yet the coolant reservoir keeps going low. The source of the leakage is the cylinder head(s).Between 2001 and 2006 GM manufactured millions of vehicles, several with defective cylinder heads. The cylinder head castings were not properly done and over time they crack. The cracks often appear in the area of the center row of head bolts. This is under the engine valve cover and difficult to diagnose. Since coolant is leaking into the engine oil, a great deal of damage can quickly occur.There will be few other outward signs other than coolant loss. Since this is coolant leaking into the oil and not water, there is normally be no clouding of the engine oil. Glycol is absorbed by the oil, but destroys the lubricating qualities of the oil. The crack also does not extend into the combustion chamber. There will not be an overheating problem, unless the coolant gets low and the radiator will not be over pressurized.
    GM acknowledges the following vehicle can be affected. Unfortunately, other than standard warranty coverage, they seem unwilling to do anything about it.

    2004-2006 Buick Rainier
    2001-2006 Cadillac Escalade Models
    2001-2006 Chevrolet Avalanche, Blazer, Silverado, Suburban, Tahoe, Trailblazer Models
    2001-2006 GMC Envoy, Jimmy, Sierra, Yukon Models
    2001-2004 Oldsmobile Bravada
    One of the easiest ways to identify the problem is with florescent dye, added to the coolant. Another is to remove the valve covers and check for coolant contamination. Steam in the valve cover area will make this quite apparent. There will usually NOT be clouding of the remainder of the engine oil. (please click images for closer view)
    One of the easiest ways to identify the problem is with florescent dye, added to the coolant. Another is to remove the valve covers and check for coolant contamination. Steam in the valve cover area will make this quite apparent. There will usually NOT be clouding of the remainder of the engine oil. (please click images for closer view)



    The affected heads have a casting mark, just above the intake port. Cylinder heads with this mark are the ones that may be prone to cracking. The cracks form in the five head bolt/oil drain areas, under the valve cover.


    The crack develops due to a poor casting and allows coolant to seep into the engine oil

    On this stripped down and cleaned head the crack can actually be seen. With the head on the vehicle and assembled, it is quite difficult to see. A pressure test with the valve cover off will verify the problem. Coolant and/or air can normally be seen seeping from the area. Florescent dye and a black light makes this much easier. (please click on image for a closer view)Proper repair involves replacement of the bad head(s). Several oil changes, in quick succession, will be needed clear the engine of coolant contamination. About every 1,000 miles for three-changes usually works. Coolant left in the engine will destroy the oilís ability to prevent wear. Coolant in the oil will also greatly increase sludge buildup.

    1995 Saturn Sw1 196K and counting
    2001 Suburban LS 150K and counting
    2004 MR2 Spyder 62K and counting
    2007 mini cooper S 60K and counting

  2. #2

    Default

    I have read about it. I was in the foundry business for a while so I did some research. The bad heads were made by a company called Castech. They have a 706 stamped on the ear of the the head. If you look at the passengerside head, just below the bottom right corner of the valve cover (towards the radiator) will have the number stamped. BUT, not all 706 heads where produced by castech. You would have to pull the valve cover and see if the castech logo is there (the battery looking thing) is this the horrible link? I can hardly see it. http://ww2.justanswer.com/uploads/Bl...t_loss_5.3.pdf I looked at my truck and it has "864" heads on it. Don't know if it came from the factory like that or they were changed by the PO

    1995 Silverado 4x4
    6" BDS Suspension Lift-3" Body Lift-Add A Leaf in rear -Trailmaster SSV Shocks-Duel Steering Stabilizer Kit -AirAid Cold air intake-
    4.56 Gears with Detroit Auburn Locker-Pro-Comp Traction Bars with duel shocks-Aluminum Skid Plate Kit-38.5" x 16.5" Mickey Thompson Baja Claws-Constant Dropping fuel gauge

    2005 Yukon XL Jet Power Programmer, Bilstein Shocks, Bilstein rear springs, Helwig Anti-sway bars, EGR Window Visors, EGR Hood Shield, Denali Headlights, Headlight harness upgrade, GE NightHawk Bulbs, White Night Rear lighting system, Russell Braided SS brake lines, PowerStop Brake pads, PowerStop cross drilled and Slotted Rotors, http://www.gmtruckclub.com/forum/sho...5-GMC-Yukon-XL
    2002 Silverado ext cab 2wd (Sold)
    2003 Yukon XL (Totaled)

  3. #3

    Default

    Thanks for that link on the TSB

    horrible in the sense that potential for defective heads and no recall or recourse outside of waranty. Coming off a coolant leak from my water pump I was wrapping up my research and then said Oh crap!
    1995 Saturn Sw1 196K and counting
    2001 Suburban LS 150K and counting
    2004 MR2 Spyder 62K and counting
    2007 mini cooper S 60K and counting

  4. #4

    Default

    I know exactly what you mean. I went through the exact same thing with my 03 yukon xl. I had a really slow water pump leak, from the gasket. It took a while to find it and I had come across the head info at that time. I had just bought the truck and was freaking out thinking I head crappy heads.

    1995 Silverado 4x4
    6" BDS Suspension Lift-3" Body Lift-Add A Leaf in rear -Trailmaster SSV Shocks-Duel Steering Stabilizer Kit -AirAid Cold air intake-
    4.56 Gears with Detroit Auburn Locker-Pro-Comp Traction Bars with duel shocks-Aluminum Skid Plate Kit-38.5" x 16.5" Mickey Thompson Baja Claws-Constant Dropping fuel gauge

    2005 Yukon XL Jet Power Programmer, Bilstein Shocks, Bilstein rear springs, Helwig Anti-sway bars, EGR Window Visors, EGR Hood Shield, Denali Headlights, Headlight harness upgrade, GE NightHawk Bulbs, White Night Rear lighting system, Russell Braided SS brake lines, PowerStop Brake pads, PowerStop cross drilled and Slotted Rotors, http://www.gmtruckclub.com/forum/sho...5-GMC-Yukon-XL
    2002 Silverado ext cab 2wd (Sold)
    2003 Yukon XL (Totaled)

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