99 GMC Suburban thermostat replacement leak

Discussion in 'General Chevy & GM Tech Questions' started by sbrodacz, Nov 2, 2012.

  1. sbrodacz

    sbrodacz New Member

    i bought a 99 gmc suburban last week. The temp has not gone above 150 degress. I replaced the thermostat yesterday. I ended up doing it twice because it was leaking. I noticed this afternoon there was still a leak from the rear of the thermostat housing. I am starting to get frusterated. Does anyone have any tips or suggestions?
     
  2. Pikey

    Pikey Moderator Staff Member 3 Years ROTM Winner 1000 Posts

    did you use any type of rtv sealer on it? I usually smear all the surfaces with it before I reinstall it. Are you sure that it is the housing and not the hose leaking? did you replace the clamp or does it still have the factory spring clamp? those things don't work well after so many years
     
  3. sbrodacz

    sbrodacz New Member

    I did not use rtv or another clamp. Do you think those could be the problems?
     
  4. Pikey

    Pikey Moderator Staff Member 3 Years ROTM Winner 1000 Posts

    It could just be leaking from the hose. I would put a new clamp on. If it still leaks then get a new gasket, clean everything up and Smear some rtv on all the mating surfaces. You do not need a lot. Just enough to close any pits in the metals. Did you make sure that the surface on the block is really clean? I use a scraper or razor knife (being carefull not to gouge or scratch the surface. Then I plug the hole with a rag and go at it with the wire wheel on my dremel or my die grinder with a wire wheel. It should look Like a mirror when you are done. Then I do the same with the housing, but I just run that on my bench grinder with a wire wheel. I also do the area that the hose slides over to knock any corrosion off. A dirty surface will not seal.
     
  5. sbrodacz

    sbrodacz New Member

    I did clean it really well. The temp gauge still shows 150/160 degrees so i am going to exhange the theromstat and buy some rtv and a new clamp. Hopefully I can get everything done fairly quick tomorrow morning.
     
  6. Pikey

    Pikey Moderator Staff Member 3 Years ROTM Winner 1000 Posts

    Make sure that you are not getting a "fail safe" thermostat. The truck will always run cold with one of those in.
     
  7. sbrodacz

    sbrodacz New Member

    I did not get a fail safe thermostat.

    I just reinstalled everything and used thermostat rtv. How long should I wait before I add coolant back in? How long do I have to wait till I can drive the truck again?
     
  8. Pikey

    Pikey Moderator Staff Member 3 Years ROTM Winner 1000 Posts

    I never wait any specified time. I put it together. Fill it and drive it.
     
  9. sbrodacz

    sbrodacz New Member

    Thanks guys. It seems like the leak ks gone.

    One of the pulleys is really squeaky. It is really hard to tell which one it is. Is there a trick to fix a squeaky pulley or do I have to replace it.
     
  10. Pikey

    Pikey Moderator Staff Member 3 Years ROTM Winner 1000 Posts

    take the belt off and start spinning them buy hand. you should be able to tell which one it is.
     

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