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  1. #1

    Default water noise in dash area

    2000 K2500 7.4L AT 4x4

    Now that the lifter noise is gone, (Seafoam is the best!) I can hear water rushing behind the dash. At first I thought it was a leaking heater core, but I notice the noise when the thermostat opens. When the engine starts to warm up, that is when it sounds like water rushing through the dash. I have noticed low coolant, but I can not find any leaks on the ground. I am guessing there is an air pocket. I also have noticed the oil fill cap has a green color on it. I suppose that means a head or intake gasket? I was going to pull a few plugs and check them for color. What do you think?

  2. #2
    Jr. Mechanic
    Join Date
    Mar 2013


    sounds a bit like water and air rushing thru the heater core,have the intake gaskets ever been changed?that you know of?any white stuff on the dipstick?if not its intake gasket,head gasket or i could say worse,get it fixed soon ,geez,they dont like antifreeze mixed with the oil, short,temp fix,leave lever on rad. cap up,or normal cap half installed,just to lower a bit of pressure.dont do this for too long,you know the results

  3. #3


    I agree with @geo1 check for an internal leak first; but, it may be just low coolant, have you ever changed it?

    '09 Avalanche LTZ - Black
    '05 Envoy XL (sold)

  4. #4


    I would agree on air is mixed in with the collant going through the heater core, if it is low coolant does not just disapear for no reason top it off and hope for the best but if you have coolant on the in the oil cap then its most likely a intake gasket problem, look at the front of the engine were the intake meets the block and look for coolant their any bit and its bad.

    2003 Z71 Silverado LS
    Access roll up cover
    Bed Rails
    Billet Grill insert
    Bed Rug
    CB with PA system
    Waiting to be installed
    Two 8in RF HX2 punch( would have 12s but they got stolen)

  5. #5


    I did have the intake gaskets replaced about 3 years ago. Had bad injectors so I just had then replaced at the same time. The GM tech who did it has been really unreliable. I have had to repair everything he touched. This was the first time I let someone work on my vehicles and the last. There is no discolorization on the dipstick. I have topped it off, the coolant bottle, several times. I took a mirror and looked around the engine, but didn't see a leak. If the intake is leaking, would the spark plugs be white on that cylinder? I don't really notice any white smoke from the tailpipe either. If it is a head gasket, can I do a compression test to verify? Thanks for the replies.

  6. #6
    Jr. Mechanic
    Join Date
    Apr 2013
    East Central Iowa


    Does this engine have a push connect fitting in the intake for a heater hose? If so look around that really close,they go bad a lot.

  7. #7
    Jr. Mechanic
    Join Date
    Mar 2013


    it is a possibility,that you will find a clean spark plug,a compression test and a pressure test,is youre best method,i would do pressure test first,one cylinder at a time,have coolant topped right off in rad. and keep cap off,it will bubble if its youre head gasket,if not its a good chance its the intake gasket

  8. #8


    same thing on my '93.... its just an air pocket. the truck is 20 years old and everything works fine. remember, you bought a truck. not a luxury car
    Gas was $1.83 when Obama took office.....

  9. #9


    Yes I have replaced the intake nipple before. No leaks there now. I have put in too much coolant for it to be only an air pocket. And why would it just start doing this? I will pressure test the cooling system first. Should this be done when the engine is warm or cold? Or does it matter in my case? Thanks.

  10. #10


    I don't know about your truck, but GM used to put automatic valves in the heater system. When the engine warmed up the valve would open and the heater core would get warm. Be sure to pressure check the coolant system with this valve both open and closed. If the pressure drops off with the valve open then the problem might still be in the area of the heater core.
    Myself, my beautiful wife
    3 - boys
    3 - minivans
    1 - '89 Chevy K2500 Silverado Truck
    1 - 27 foot travel trailer
    Not enough family time!

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