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  1. #11

    Default Dex Cool is not the only reason fo gasket failures...

    That lower intake manifold gasket problem is not solely due to DexCool. If DexCool is even responsible I'd be surprised. It was a ****ty design for the gasket. GM used a real gasket on both sdes of the engine. Then in the front/rear of the engine you have to bead some silicone gasket material. After a while it seperates and leaks. We went about 75K on 2 - 3400 V6s and did both of them. Exact same leak in the exact same place. Front of the engine, where the sealer is laid down instead of a real gasket. Stupid engineering. Instead of the gasket material GM sells. We used some gasket compound Toyota has for their manifolds. Both cars are on the road with no leaks. Servied at ~75K. 1 of them now has ~130K and the the other is at ~175K. Both were refilled with DexCool during the reapairs.

    No other GM car our family owns is screwed up due to DexCool. No cooling system leaks. Only those V6s. The only thing I'd say is flush the stuff a lot sooner than the factory says. Use a good system flush solvent. If you don't trust DexCool use something else. Just remember once you green you can't go back without a major cleaning. The DexCool will contaminate if you put any green in it.

    The side effect of DexCool is it does build up that light brown gooey crap in the tank and the radiator core. It's the trade-off for using something that is supposedly not as chemically harmful to the environment as the Prestone green anti-freeze.
    2006 Chevy Silverado, 5.3L, Z71, Extended Cab. Tow Mule.
    2002 Chevy Corvette Z06, 5.7L, Slightly Modded. Tow Payload.
    2005 Craftsman Riding Mower, 17hp, light mods.

  2. #12
    Master Mechanic Dr_Zero's Avatar
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    Mar 2006
    Sunny Florida


    bump for new folks
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    1996 GMC Suburban SLT
    1997 GMC Yukon SLT

  3. #13


    Good information. I will never use Death Cool in my vehicles.

    The whole "low coolant" causing the problems is also a myth.
    When you hear hoofbeats, look for horses not zebras.

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