I have a 96 F-150 4x4 5.8L. I live in canada an i only drive the truck for the simple purpose of the 4 wheel drive during the winter because my other car is a Cobra...an they dont do very well in the snow


Anyhow during normal winter days the temp where i live is around -20F to about 7F..I usually start the truck about 40 minutes before i leave and when i get in it the temp gauge is in normal but the heat just doesnt get hot at all...it gets warm...but i can drive around all day with the heat on max and my jacket on and still be cold. I dont expect it to get to 100F but i expect at least 75-80F.

As far as i know the heater core is fine, no fog near the windshield, no sweet smell comming from behind the glove box and the coolant was changed about 4 months ago. Its been like this sense i bought it about 3 years ago. I just never got around to fix it....does anyone know whats wrong?

 

i've never had to drive my truck in that cold of weather so i dont know how much it affects it exactly. but when i drive in 20*f or less it takes forever to get warm inside the truck but it does get warm eventually, so i know cold weather makes a big difference. can you feel antifreese flowing through the heater hoses? could be a clogged or partially clogged heater core. is there a difference sitting at idle compared to cruising? what size cab do you have?

 

standered cab, an no..no difference sitting at idle compared to cruising. The hose going from the radiator to the block (where the thermostat is) gets pretty hot...almost too hot to hold onto for more then like 10 seconds.

It has 92K miles as well, the engine is completely stock

 

You either have a clogged heater core or the blend door has something blocking it from going all the way to full heat position.

Pull the cover off and see if anything is blocking it, if not you have done most of the work of replacing the core.

The cover/panel:


Blend door:

/

 

Thank you VERY much for the detailed instructions. Im off work tommarow some im going to pull it apart and probably while its out change out the heater core and flush the system again. Hopefully that will fix the problem...it sounds expensive but its better then a cold truck in -20*F

 

I've fixed a few of these over the years.... it is usually a partially clogged heater core on a 12 year old vehicle that has probably never been flushed.

Take both the inlet and outlet hoses off the heater core at the firewall.
Put a hose up to one side and let water flow through the core.
Sediment and all kinds of brown/tan rust and grey stuff will come out.

DO NOT put the hose dirrectly connected to the heater core inlet or outlet.
It could burst your core.

Let it drain out and try the other side where the water came out.

Repeat a few times until water runs clear (no sediment) and water runs freely.

Let drain, reattach hoses and refill colant system.
I'd bet it will work fine again.

If you can't get it to flow easily after a few tries, you'll need to replace the core.

 

Just to add if you are going to replace it.
1) Remove the glove compartment.

2) Remove the RABS module (two Torx screws) and then disconnect the harness
from it.

3) There's another box next to the RABS, pull it DOWN and off the metal tabs
and out of the way, careful not to bend the tabs, very soft metal.

4) Remove the 6 8MM screws from the core cover.

5) Release the vacuum lines from the cover, one on the bottom and right side of
cover, CAREFULLY place the line(s) to the side.

6) Gently pull the cover away from the core, you will need to release the blend
door cable from the cover, there is a tab you push from behind to
release it.

7) Once the cover is removed, disconnect the send/return lines from the
core located under the hood.

8) Pull the old core out, put the new one in (or unplug your existing one)
connect the lines and replace the cover, fasten it, attach cable and
vacuum lines, replace the module on the metal tabs, and re attach
the RABS module.

DONE!

To add to it, make sure you replace the foam gasket to prevent the core from bouncing around and also, you will want to reconnect the send/return lines **BEFORE** you re-attach the cover incase the core gets pushed back when attaching the lines.