99 Silverado No Heat
 

Had the truck in the shop mechanic stated thermostat was bad also claimed the water pump was "seeping" through the weep hole now ive have been under the truck in my garage several times before and saw no fluids so i found it hard to belive the "seeping" thing also fluid level has been were it should be.Wanted $500.00 to fix both I have a warranty but these issues are not covered go figure. So I told them to go ahead and change the thermostat. Seemed to work better for a few days when the outside temp has been above 30 degrees and now that it has been alot colder it will not blow hot air at all would a "seeping" water pump cause a no heat situation? I do not want to take it back and have them just keep throwing parts at it $$$$$ until they find the issue. Thanks in advance!

What temp Thermostat did he install? You may have a clogged line to your heater core and it may need to be flushed. Also you have a inlet valve before the heater core that allows you to generate heat before the engine is warm. These valves are notorious for leaking and failing. It is located (facing Engine) all the way to the back on the left side of the motor, low against the firewall. It will be a rubber line to a metal gooseneck that just pops into the inlet with clips that hold it in place. More than likely you will break the clips when you take it apart. You can buy the whole inlet for about $5 at any of you local part houses. Hope this helps. Good Luck!

Do you still have Dex-Cool anti freeze in your sytem? If there is get a flush and replace it with something else. It will gel up in your system and heater core. Noticed my heater getting weak a few years back, and did this and never had a problem since.

Yup it sure does I've heard that before leave it to GM to come up with there own coolent that causes issues.

pull your return hose to your heater core and flush it. its just gummed up.