If you've installed an LT1 engine from a Camaro or Firebird into your automobile, or if you're still driving your 1990s Camaro or Firebird, you'll eventually need to address the aging thermostat that stands between a cool-running engine and a complete engine overhaul. Chevy's 1990s version of its LT engine does not differ from older models in very many ways, including the location and maintenance methods for the cooling system.
Remove the upper radiator hose from the thermostat housing by removing the retaining band that holds the hose to the thermostat housing. Pull the hose off the inlet spout. It's common to replace the older, spring-style band with a toothed band clamp. If this has been done, you will need a nut driver to remove the band clamp.
Remove the two bolts that hold the thermostat housing onto the LT1's intake manifold and lift up on the thermostat housing to remove it from the intake.
Pull the old gasket off the intake manifold and discard it. Pull the old thermostat out of the intake manifold of the LT1 and discard it. Neither item will be reused.
Wipe the mating surfaces of the intake manifold and the thermostat housing with a clean cotton towel to remove any old fluid and gasket material.
Cover the mating surface of the thermostat housing cover with a thick bead of RTV silicone gasket maker and let it set for 10 minutes, or follow the RTV manufacturer instructions located on the packaging.
Place a new thermostat into the intake manifold with the correct end facing upward. The top will be marked as such.
Place the thermostat housing onto the intake manifold and bolt it into place using the bolts you removed in Step 2. The RTV will squeeze out slightly. This is okay. Do not wipe it off.
Reattach the radiator hose with the original spring clamp or change it to a more modern band clamp.
