Hello all

Hoping someone can help me out

So I have a 98 f150
I replaced Heater core as it was leaking
Probally should have changed blend door but didn't

So I fired up the truck and had no heat both upper and lower rad hoses cold
Changed thermostat upper rad hose hot lower cold but I had heat

So been driving for about a week now no heat issue
Then today I take it out on the highway and I no longer have heat

So I thought maybe I'll need a winter guard
But I got home and left my truck running yt
To see if it would heat up and hasn't

Any thoughts

 

You may have an air lock. Park it with the nose facing uphill, pull the cap, and let it idle for at least 20 minutes with the heater running. Then top it off.

 

Putting a vacuum on the rad should work as well right ?

 

No. It has to burp "naturally".

 

I was under the impression the degas bottle is already the highest point in the system and has a self-venting cap.

 

The system has to build up to 15 psi before the cap will vent. The cap has to be OFF to burp it, and the higher up the front end is, the easier it will happen.

 

Ok
I have burped my system 3 times
Rad fluid has never changed but I do have a little heat not great

So I drained rad
I have refilled with a vacuum filler

Still don't have great heat

I have confirmed that my blend door is opening all the way

 

If your coolant has never been changed, you probably have something partially blocked with crud - like the heater hoses or the restrictor.

 

When I did my heater core I changed coolant and did a compete flush

Also can hose through till it ran clear
And ran hose through both heater core lines till ran clear

 

does the upper radiator hose get hard and hot?