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03 Silverado 5.3 Mass Evap issue

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by toyhauler, Dec 15, 2011.

  1. toyhauler

    toyhauler New Member

    My 03 Silverado 5.3 Vortec is showing a check engine light for a Massive Evap Leak. Any ideas on route for weeding through the issue??
    Anyone ever have this issue before/possible fixes?

    Thanks
  2. Pikey

    Pikey Moderator Staff Member ROTM Winner 1000 Posts

    I have the same issue. Check your gas cap seal. I put a new cap (from the dealer) on and had the still had the same issue. So I checked the filler neck and it had a bunch on corrosion on the lip, I cleaned it and it has been ok for a while now. Next I would search the forum with your code, there are tons of post here about what to check. The best way to test the system would be smoke test it. To do that look on the drivers side of the motor you will see a green cap over a valve on a plastic line. It you take the core out of the valve, then make an contraption to hook a hose to it (it could just be a hose slid over the port and sealed tightly). I have seen guys use a 2 liter soda bottle with a hole in it and a cigarette to make a smoke machine. They just drilled a hole in the cap and pushed a hose barb thru that will fit the ID of the hose you have connected to the evap line. Then light a smoke, stick the butt end into the backside of the hose barb, screw it onto the 2 liter,(cigarette inside the bottle) put your finger over the hole in the bottle and squeeze. Let your finger off the hole, get the bottle back to normal shape, finger on the hole, repeat. It may take a few cigarettes to get the system full. I have been told that if you take off the gas cap it will fill the system faster, when you see smoke coming out of the filler neck, put the cap back on. Fill her up with smoke and look for leaks. I have only seen one guy do it, it was pretty neat and worked. But, with the cost of cigarettes here it may be cheaper to go to the dealer!!
    Last edited: Dec 15, 2011
  3. TRPLXL2

    TRPLXL2 New Member Platinum Contributor 1000 Posts

    Pikey that is an awesome tip!! I just tryed to add to your reputation, but it said I wasn't allowed to??

    ANyways I have this same code coming up on my 05' Silverado 6.0, and the truck only has 22,000 miles so it baffles me. I am seriously going to try this, I love things that you can do yourself. 5 stars!!
  4. Pikey

    Pikey Moderator Staff Member ROTM Winner 1000 Posts

    Thanks! I don't know how the reputation thing works anyway :)
  5. toyhauler

    toyhauler New Member

    Thanks for the tip.I`ll have to look into trying that and see what the results are.
  6. Pikey

    Pikey Moderator Staff Member ROTM Winner 1000 Posts

    Good Luck, I hope it works out for you! Let us know how it goes
  7. johnb9173

    johnb9173 New Member

    Man thats a great idea but how do you create pressure in the evap system consistently so the smoke will be forced out.
  8. Pikey

    Pikey Moderator Staff Member ROTM Winner 1000 Posts

    I assume that if it is a large leak it will come out without a bunch of pressure. if the vent solenoid is stuck open, it is going to come out of there pretty quickly. He said that he had a massive leak not a small one. I bet that you could find a way to put a quick connect from the air compressor onto the back of the 2 liter. Some seal-all, a washer and a nut would probably work. Hook the compressor up (regulator set at real low pressure, Like 2-5 psi, most unmodified 2 liters can handle 80psi easily, but drilling a hole to put the quick connect in greatly reduces its structural integrity, Just did an experiment in a material mechanics class concerning exploding bottles. Plus, you don't want to blow another component of the evap system out. ). That would smoke the cigarette for you, no squeezing the bottle, and keep the system under pressure.

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