Mysterious Coolant Leak

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by Cal_truck22, Feb 2, 2008.

  1. Cal_truck22

    Cal_truck22 New Member

    Hopefully someone can help me out. I have a 2000 Silverado with the 5.3L engine. Recently, I have been losing coolant at a slow rate. I have had the cooling system pressure tested by a dealer and an independent mechanic and both say that there is not a pressure leak in the system. I have checked the oil and I do not see any indication of antifreeze in the oil, so I do not suspect a head gasket problem.

    Also, there is no visible signs of coolant leaking from the system (I see no coolant on the ground under the car and the engine compartment does not smell of coolant). So, if the pressure is good and the head gasket appears not to be the problem, where is the coolant going? I have changed the radiator cap on the surge tank, but this did not appear to help. Has anyone else seen a problem like this? I am going crazy (not to mention spending a lot of money doing pressure tests!) with this problem.

    Anything will heip. Thanks!
    Last edited by a moderator: Feb 8, 2008
  2. 84fiero123

    84fiero123 Epic Member 5+ Years 1000 Posts Platinum Contributor

    First welcome aboard. [​IMG]

    If you don’t have a pressure leak in the system I really don’t think you have anything to worry about.

    But if you start loosing more coolant, more quickly I would have the test done again and this time with a die that will show up under a light. It just makes it easier to see where the leak is coming from.
  3. Cal_truck22

    Cal_truck22 New Member


    84fiero123, first thanks for the warm welcome. Second, thanks for the truck advice. Right now, the temp does not budge from the normal temp, so it appears it is not a big deal. It is just inconvient to fill the surge tank with 1Q of antifreeze every 1.5 months or so. Hopefully it does not get worse.
  4. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    Check the surge tank and connecting hose, this is the only part of the cooling system that isnt pressurized and wont show a leak when you do pressurize the system.
    Almost all surge tanks are plastic and they break down from the heat after a while.
  5. Duramax04

    Duramax04 Rockstar

    I have a mystery machine like that also.My old 97 Z-71 is losing antifreeze but i can smell it when it is setting still at an idle but there is never any signs of a leak. I can park it on the concrete or in the garage and let it set overnight and everthing is dry the next morning. I probably add a quart every couple of months.I have a pressure tester, guess i should put it to use,huh? Just might do that today.
  6. Cal_truck22

    Cal_truck22 New Member

    Let me know what you determine from your pressure test. If your problem is anything like mine, the pressure test will come out fine, and the mystery will continue.
  7. Duramax04

    Duramax04 Rockstar

    Cal, your exactly right. Pressure test was good and cap checked out okay. Back to scratching my head.
  8. JayMack75

    JayMack75 Former Member

    I had a similar problem on my old silverado. The source of my problem was at the back of the intake. When the engine was warm it would leak, but would burn off before anything touched the ground. When it was cool, nothing leaked at all. It was a pesky problem and I sold the truck (unfortunately) before I was able to fix it.
  9. Cal_truck22

    Cal_truck22 New Member

    How did you determine that the intake gaskets were the problem? After I drive the truck for a while, I lift the hood and try to smell any coolant in the engine compartment. However, I smell nothing. If it is only leaking when driving, would I be able to smell coolant in the engine compartment? The problem in my truck is starting to get a little worse, so I am getting more concerned about the problem. Thanks.
  10. mack1611

    mack1611 New Member

    Have you located your mystery leak?
    I'm having the same problem on my 2001 c1500. No visiable leak but I need to add a quart of coolent about once a month.

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