Q: How to remove and install the thermostat on Cadillac ElDorado and Fleetwood?
A: For 4.5L and 4.9L engines, drain coolant, and remove the upper air filter assembly. Next, unscrew the two bolts of the upper thermostat housing, then remove the thermostat. Install a new thermostat and O-ring, reattach the housing, and tighten the bolts. Refill the system, start the engine, and make sure there are no leaks.