Question about 1994 GMC Sierra

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Oily coating inside of windshield

94 gmc sierra stepside pick up, how do I find and fix this interior problem. happens using ac or heater, assuming hoses going to blower and or cooling unit, it is inside nasty coating of antifreeze? ac freon?

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  • Glenn Bubb
    Glenn Bubb Aug 01, 2010

    added freon its gone, ac is hot air. sooooo how to fix?

  • Glenn Bubb
    Glenn Bubb Aug 02, 2010

    i want to repair it, can i use a can of sealent? i need to know how to fix it, and where it is located, the core .

  • Glenn Bubb
    Glenn Bubb Aug 05, 2010

    ok got the ac problem ill get to finding the leaking connection,, one other thing, at high speed check engine light comes on, checked all the causes ,gas cap, fluids etc, I was told not to worry about it, m the only thing i did to cause this was add lukeoil, due to some smoke on ignition, and 10/30, it is a 94 gmc sierra. it takes 5 wieght. should i ignore it? it does not come backon if i turn off the truck and restart it. hmmmm i dont want to break down on long distance run.



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Coolant will be orange or green in color
Freon evaporates although if an AC leak a slick oil can appear

Posted on Jul 31, 2010

Testimonial: "yup its the freon im sure, lack of thr "flavor" of antifreeze, which i experianced with my chevy g20, and the light oily film, ac is warm"

  • 1 more comment 
  • frank thomas wilson
    frank thomas wilson Aug 01, 2010

    If the AC is not to be repaired or used the only way to get the oily mess cleaned up is to remove the evaporator case and cleaan out the inside of it or remove the evaporator core. I would use an engine cleaner or oven cleaner to clean away the oil and flush with water. Removing the core is the best way to do it and wipe away the mess

  • frank thomas wilson
    frank thomas wilson Aug 03, 2010

    the ac unit has all sort of fittings with o rings that seal the connection. Most people do not use ac in the cooler months so the seals will dry after a few years and tend to leak. Leak detectors can be used to find the leak or ac dye that is added into the liquid line which is the line you use to recharge the unit

  • Glenn Bubb
    Glenn Bubb Aug 05, 2010

    ok thanks.



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