Q: How to check and replace a thermostat in a cooling system on Chevrolet Avalanche,Silverado,Suburban,Tahoe,GMC Sierra,Yukon,Yukon Denali and Yukon XL?
A: Before assuming the thermostat is to blame for a cooling system problem, it is important to check the coolant level, drive belt tension, and temperature gauge (or light) operation. To remove and install the thermostat, follow the steps for either the V6 or V8 model. Also, clean the mating surfaces, install a new rubber O-ring around the thermostat, and check and replace hoses and clamps as necessary. Installation is the reverse of the removal. After installation, refill the cooling system, run the engine, and check carefully for leaks.