1995 GMC C1500 Thermostat installation

  • 1995 GMC C1500
  • 4.3L
  • V6
  • 2WD
  • 252,000 MILES
I bought a new duralast thermostat and duralast gasket from autozone and am wanting to know if the gasket goes in first and then the thermostat on top of the gasket or the thermostat first and then the gasket on top. Also should I use some RTV silicone sealant on the thermostat housing because it has no gasket at all.
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Saturday, November 8th, 2014 AT 8:40 PM

1 Reply

The most important step is to be sure all the old gasket material and any rust are completely cleaned off both surfaces. Many mechanics will remove the thermostat housing completely and run it over sandpaper on a sheet of glass to insure it is clean and flat. You'll see a groove in the intake manifold for the thermostat to sit in. Be sure that is clean too so the thermostat doesn't stick up.

The gasket goes on next. I use a light coating of silicone gasket sealer on both sides to make removal next time easier. It will also fill and seal any gouges caused by over-exuberant cleaning. I'm familiar with Chrysler's gasket sealers. The gray stuff seals and bonds through a light film of oil residue, it gets harder, and it's harder to remove. For this application you want the black stuff that stays more rubbery. Other dealers have the same sealers with their own names on them. The sealers are just extra insurance against a leak. There's a gasket in there, and that's all you need, so if you're going to buy a whole tube of sealer just for this job, I wouldn't. Most of the time once the tube is pierced, the rest of the unused product gets hard within a few weeks.
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Saturday, November 8th, 2014 AT 10:42 PM

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