07 Silverado Coolant loss

Discussion in 'General OFF TOPIC' started by Mavagrand, Feb 10, 2012.

  1. Mavagrand

    Mavagrand Senior Member

    I know this isn't a Chevy forum but I also know it is full of good mechanics. Looking for some help with my 07 Chevy Silverado Classic. It has the 4.3L V6 with automatic transmission and has been bullet proof for all 51K miles. She recently threw a code which, according to the dealer, indicated my thermostat had went bad. Dealer wanted to charge me 200 to change the thermostat, I told him I would do it and paid 21.00 for the part. I did have the dealer change the oil while I was there.

    Anyway, that was a couple of weeks ago and I haven't changed the thermostat yet figuring, since the truck has never run hot that either it wasn't a problem or the dealer was wrong. Well, the check engine light came back on today. I started looking around under the hood, figuring I would change the thermostat tomorrow. How shocked was I to discover there is no radiator cap, or at least not one that I can find. The top of the radiator is covered by a plastic shield.

    While underneath the hood I checked the overflow jug, it was bone dry, no coolant in it at all. I filled the jug and drove the truck to dinner (10 miles round trip). Got home and checked, the jug was about half full. There is no apparant coolant leak, I checked all the fittings, hoses and everthing. There is no smell of burning coolant and no water in the oil that I could tell.

    My questions, anyone know where the coolant might have went? and does anyone who owns this model/year know how to check the coolant level?

  2. STEVE07

    STEVE07 Well-Known Member Staff Member Super Moderators

    The GM has vortec aluminum heads and a cast block,sometimes the gasket material won't stand up to the difference in expansion. Change out the head gaskets.To find out which head gasket has gone bad do a compression test,or save yourself the trouble and do both.
  3. orgredneck

    orgredneck Member

    check coolant level at overflow jug
    should have full cold and hot marks.
    GM has had problems with intake gaskets,
    heater core could be seeping,
    do you get a film on windshield,
    pressure test to find leak.
    since you have no overheating problem,
    thermostat might get stuck open,
    if not getting up to operating temp.it will through a
    temp. code.
  4. fin_676

    fin_676 Experienced Member Staff Member Moderator Contributor

    Knowledge of how a liquid cooling system works may help and if things have not changed over the last few years ill try and explain how they work
    Cooling systems are sealed and pressurised being under pressure raises the boiling point of the coolant to maintain the correct pressure a pvrv is used pressure vacuum relief valve that works on a +10 and -1 of atmospheric pressure
    as the coolant heats up and pressure builds up in the system the pvrv will open and allow pressure to be released in the form of steam which should condense back into coolant when it gets to the expansion tank (overflow)
    when the engine is switched off and the coolant cools it will create a vacuum in the coolant system the pvrv then opens and allows sufficient coolant to be drawn back into the system from the expansion tank
    as the cap on the expansion tank is vented some steam can be lost to atmosphere at times

  5. Iceman24

    Iceman24 Well-Known Member

    Sometimes...it's a simple air bubble in the cooling system that worked its way out. I say fill to line & monitor again to see if any of the above (more extreme) recommendations are necessary...
  6. dbmg

    dbmg Guest

    I have used this product with great success if there is a gasket or rad leak. Will not work with a water pump leak.
    HDC 12-60 gram blister packs per case
    Heavy Duty Concentrated Tablets. One package of six 10 gram tablets for 6 & 8 cylinder vehicles.
    Bar's Products Line
  7. rhino 2

    rhino 2 Active Member

    Old street mechanic's trick i've used a few times. [caveman style]
    A little red pepper in the radiator.
    Last time i used it was 3 years ago in a Can Am Spyder, held for 3 years.
  8. dbmg

    dbmg Guest

    I used to get laughed at years ago for doing that. The reason I started to use the Bars gold tablets is that they are made out of Ginger and could not find a negative using them....:s It all nautural.....
  9. HDDon

    HDDon Experienced Member Contributor Retired Moderators

    I've read the post and Mavagrand is correct we have some great mechanics on the forum. I have a question about the original statement, he stated that he found no radiator cap. Is this possible or is it placed in such a way that you can't see it?
  10. dbmg

    dbmg Guest

    06-09 Chevrolet (Chevy) Silverado Pickup Radiator

    It appears that there is no rad cap. I have seen over the years others that have no rad caps and you fill the system at the thermostate. The block through stat and rad though the removed upper hose at stat. rest in overflow bottle. Older GMs used to have a rad cap on a auxillary tank away from engine not attached to rad.