LT4BUD

The 96 LT4 has factory bleed valves on the thermostat housing.

grapeknutz

So does my LT1, that bleeder is to relive the air after the thermostat opens the purpose of drilling the hole in the thermostat is to relive the air trapped under the thermostat :thumbs:

LT4BUD

The bleeders are used when installing a new thermostat or when refilling coolant after draining. You open the bleeders and add coolant until coolant start flowing out of the bleeders. At first air comes out, then bubbly coolant, then solid stream of coolant. You do this before you start the engine.

I think the real purpose of drilling holes in the thermostat is to increase coolant flow as even when most thermostats open, they still restrict coolant flow to some extent.