New Member S/W Ontario Canada, With Questions??

Discussion in 'General Chevy & GM Tech Questions' started by Old Iron nut, Mar 6, 2013.

  1. Old Iron nut

    Old Iron nut New Member

    Just got a 1998 Chev 3500 Cheyenne 1 ton with a 350 engine. Motor was replaced about 5 years ago with a brand new crate motor from GM. Original motor failed due to leaking intake manifold gasket. The present motor also has the same problem-antifreeze in the crankcase, also attributed to leaking intake manifold gasket. What years did this problem start and when did it end? The local rebuilder advises me that this was a common problem. Does anyone know if this a machining error or poor gasket on the part of GM? Apparently there is a replacement gasket that solves this mess. I don't have the motor out yet and will have to wait for the climate to warm up before I pull the engine. Cheers, Old Iron nut.
    PS. Truck has low mileage.

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  3. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    You should be able to fix it without pulling the engine. I had the same problem on a 4.3 and fixed it by removing the intake while still in the truck.

    Do a google search on Dexcool antifreeze and leaking intakes, that should answer all questions.
  4. Skippy

    Skippy Member 2 Years 100 Posts

    Oh yeah. Ray's got the right of it. As soon as I read the magic "5 years" mark, I instantly thought Dexcool.

    That stuff needs to replaced every 2 years on the spot. The additive package just isn't sufficient to protect your engine's aluminum parts. Great for cooling, but nasty on gaskets!
  5. Old Iron nut

    Old Iron nut New Member

    Skippy. don't know whether or not the engine had Dexcool or not, the problem started about 2-3 years after the new motor was installed. The truck has not been plated for the last 2 years. I don't know if Dexcool is the same as the Cat long life antifreeze but I know the Cat stuff does not have to be changed every two years. There are a few other GM owners with the same problem of leaking intake manifolds. Cheers, Old Iron nut.
  6. Skippy

    Skippy Member 2 Years 100 Posts

    Dexcool, btw was supposed to last 5 years or 150K miles. Any dexclone antifreeze is likely to have the same corrosive properties. Can I guarantee the intake manifold leak is a direct result of the antifreeze by evaluating a forum post? Absolutely not! LOL

    That being said, I'd still take a peak at what the formulation was. And if it's a Dexcool clone, I'd still be changing the stuff every 2 years... It's just not worth a bum engine. Too much evidence that shows Dexcool formulation DOES last 5 years, but the engine in which it's operating DOESN'T. *grin*

  7. Old Iron nut

    Old Iron nut New Member

    Many thanks for the reply, Skippy. I have been using the long life Cat antifreeze and Mobil 1 synthetic oil in all my equipment and have not had any problems. I'm hoping to remedy the problems in the 98 Chevy after I tear it down and correct same. Funny, I don't have leaking intakes on my old Cats. Only been working on them for over 40 years. Cheers, Old Iron nut.

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