Sorry to post something else about heater cores and such, but I've searched and can't find exactly what I'm looking for. Just replaced a leaking heater core in my 2000 F150 4.6L. Before replacing, I had great heat, just a bad smell of antifreeze. Now, I have little to no heat. Every once in a while it will get warm, but usually stays cold. Seems like it only gets warm when it's sitting still and I rev the engine. While driving it doesn't get hot at all. The other day I was driving home and the engine overheated, so I immediately changed the thermostat thinking that it was also causing me to have no heat. Put in 2 gallons of 50/50 coolant and still have no heat. I can still hear the sound of liquid moving when I first turn on the engine and give it gas, but it goes away after just a minute or so. I'm thinking either I still have a good amount of air in the system and need to burp it and add more coolant or my water pump has decided to take a dump. The truck has 130,000 miles on it, so it wouldn't be a big surprise, just curious if anyone has a more solid idea about what's going on. Any help or advice is greatly appreciated!

 

I feel I should also add that the first time I changed the thermostat (about 2 years ago, and that time the thermostat had actually managed to get itself wedged and took a good amount of prying to remove) I had a good amount of coolant left in the upper rad hose. This time I had none. I had just changed the heater core a couple of days before, so I know it wasn't low on coolant.

 

You are airlocked.

 

Well, guess I'll try to find a decent place to burp it, then. I may decide to go ahead and change the water pump this weekend anyway. Thanks for the reply

 

Since your not posting in the right forum, you most likely haven't searched all that effectively

The correct forum - https://www.f150online.com/forums/hvac-69/

Don't post there now, that would be double posting. That's worse than.

A Moderator can move your thread for you tho, - if you want to email one.

Check the pump for wobble, coolant around the weep hole or a bad T-stat. They perform the best with the 192's and 194's.

Hard to Burp, use the procedure below -

 

Thanks for the reply and useful info. I did see the HVAC forum when searching, but for some reason didn't see it when I went to make this thread. Now I see that I didn't look down far enough. I will grab a couple more jugs of coolant tomorrow and try to get the air out of it. Luckily work is only a couple miles away, so the truck doesn't get too hot back and forth from home.