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Thermostat won't fit!!!

Discussion in 'GM Powertrain' started by sc99z71, Mar 27, 2009.

  1. sc99z71

    sc99z71 New Member

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    So I go to Advance Auto Parts to get everything I need to flush and fill the radiator as well as change out the thermostat while it was empty. After draining the coolant I get the old thermostat off and try to put the new one on and it wont fit. Anybody else have this problem? I jumped on my motorcycle while I still had it off to go see if Advance had an optional one that may fit and they said this was the only one they had listed for this truck. I then went to Autozone and O'Reilly's and theirs was almost exactly like the one from Advance. Can anybody help? If you found one that fits where did you get it from? By the way its for a 99 Silverado 1500 w/ 5.3L.
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  2. jlsparky7

    jlsparky7 New Member

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    Couple things

    There should be a MM measurement stamped on the thermostat somewhere like 54mm or something like that. Just get the thermostat that has the same measurement.

    If there is a gasket usually there is a rubber bump that sticks out 1-2mm. That has to be lined up with the dent in the thermostat housing for a proper fit.

    Hope this helps.
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  3. Dr_Zero

    Dr_Zero New Member

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    Did they sell you one with a black gasket stuck on to the thermostat?

    The old style was like that and if you pull off the black ring it might fit cause when I look it up the newer models show a different style O ring gasket.


    Ummm dumb question time but since I have never owned a 5.3 is it supposed to come off the housing?

    They sell it as one piece ????

    (Curiosity has got me now so I called the local advance and gave them the info you posted for the truck and they dont even carry that thermostat.)

    [​IMG]
    Last edited: Mar 27, 2009
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  4. mjalstad

    mjalstad New Member

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    Are you sure they are looking up the new body style 99 Silverado and not the 99 K1500? Maybe ask them if they have one for a 2002 Silverado 5.3 and see if they come up with anything different.
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  5. sc99z71

    sc99z71 New Member

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    I watched them look up the info for the truck to make sure they were not looking at the K1500, and they did pick Silverado 1500. They even looked themselves to see if the same part number came up for a 2002, and it did. Yes they do sell it as one piece with the housing and all. The old thermostat that was on there was actually two pieces and the thermostat popped in with the rubber gasket. The one they sold me was one piece meaning you could not take the thermostat out of the housing. I might have to go to the dealership for this one. Thanks for al the replies...
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  6. Dr_Zero

    Dr_Zero New Member

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    #6
  7. sc99z71

    sc99z71 New Member

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    Yes that was the part number at Advance Auto, and I tried fitting that thing every which way but backwards and it just would fit. The part that was keeping it from fitting wasn't the housing. On the thermostat from Advance the actual thermostat is held in the housing with braces that come off the housing to hold the thermostat, those braces are what was keeping it from fitting. If you look at the pic a few posts up it is the wide metal piece that is coming about halfway down the thermostat.
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  8. sc99z71

    sc99z71 New Member

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    Would it be possible that a thermostat from a 98 K1500 fit??
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  9. Dr_Zero

    Dr_Zero New Member

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    Ok called a fellow I know at advance and he said to try one of these out depending on what temp you want

    Stant part #
    13009 190 degree
    13008 180 degree
    13006 160 degree

    and the gasket I think he said was a 35602 felpro

    He said it sounds like you got the old style block
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  10. sc99z71

    sc99z71 New Member

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    Thanks for info I will check it out....:great:
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  11. daddytech

    daddytech New Member

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    I was kind of thinking the same thing , in 99 they produced 2 different motors one was the 350 the other the 5.3 litre was kind of wondering if maybe they had looked up the thermostat for the 350 and gave you that one instead.
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  12. Dr_Zero

    Dr_Zero New Member

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    any update?
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  13. sc99z71

    sc99z71 New Member

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    Have been way too busy to try anything, but when I do I will post what the outcome was.
    Again...thanks for all the input.
    #13

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