97 Blazer Heater

Every morning in my 97 Blazer, the engine temp shows the thermostat is working properly after 5 miles. If I am going down the road, hot air comes out of the dash, and the floor. If I am sitting still, it only blows cold air. Any thoughts?

You may have air in the system, i know there was a post on how to bleed the system, do a search for it . You can also buy a tool that bleed the system for you.

I had the same problem with my '00 I replaced the thermostat...didnt fix it...flushed the heater core...didnt fix it....and thought well maybe the water pump was going bad....well to make a long story short I lost the rad cap when I flushed the core...darn kids musta took it..so anyway I put a new rad cap....safety style....and it now will run you out of the vehicle with nice hot air at all rpm's...so lesson learned the system needs pressure to flow...try the cap first 10 dollar fix...and on a side note when I flushed the coolant it was not bad the core flows like new....

New rad cap and might be a good time for a cooling system flush.

Make sure you back flush the heater core.

Thanks mates. I'll try to find out how to bleed the air out, but I don't know where to look. On google or were? I know I changed the water pump, the thermostat, and the rad cap. I'll replace the rad cap anyways. You mates are the help.

Easy really, put the front of the truck up on ramps and remove the rad cap from a COLD engine.

Start it up with the heater on full blast and add coolant to the rad as it drops when the thermostat opens.

Also good once warmed up to have the engine revving up in the 1500rpm-2000 range to get the waterpump circulating the fluid properly.

Puttting it on ramps will have the rad as the highest point in the cooling system and air will travel to that point to escape.