I just paid to have a new heater core installed. But now the heat isn't working much. How do you locate and replace the thermostat? Thanks

 

follow your top radiator hose from the radiator to the engine, where it connects to the engine is called the water neck, the thermostat is under it. should only be 2 bolts and the hose to get to it....

 

they are very easy to replace, but im not sure it will fix your problem. i just replaced the one in my s10, and while it helped with some temperature guage fluxuation problems, it has not affected the fact that i still need to flush/ replace the heater core

 

See if your radiator needs.... dare I say it,........ Burping! Put the heater temp setting on hot,Take the radiator cap off, start the truck and let it run till after it reaches operating temp & no more bubbles are visable in the opening of the radiator, topping the fluid off as needed durring the process. If no bubble appear & no further fluid is required, then I'd consider the thermostat. This procedure should have been done by the mechanic but often isn't. The process of replacement of the thermostat and refilling will usually cure an "air in the system" problem itself. Whether the thermostat itself was needed or not.