I have a 2004 5.4 F150 4X4. I live in northern Ontario. Our temperature got down to -20C (-5F). I fired up the truck and the engine heated up to the normal temperature but the heater never gave out heat. I took it dirctly to Ford dealer. They of course left it sitting instead of checking right away and when they checked it all working fine. They figured it was the blender motor so changed that. Next two night -15 C (5 F) and all was fine. Third night -22C (-8F) engine heated up no heat from heater.

From the start the service person kept saying thermostat like I was stupid or something. Can't be thermostat or engine would have overheated. They tried it after letting it sit and of course everythig worked fine. I said something is thawing out then and working after the heat works through the firewall. They said thermostat thermostat.

They ran temperature test and found engine not heating up past 188 degrees. Kept it overnight but not that cold so it worked. So changed thermostat. How that is going to do anything I don't know. Anyway since then (3 days ) temperature above the critical temp of zero (I think the critical temp) and working fine. Anyone else ever had this trouble. Any suggestions?

Murph.

 

I have no historic references to help from here where it never gets that cold, but a couple thoughts...

For one, a stuck open thermostat would not cause an engine overheat, but could cause the coolant not to warm up.

For another you need to see what the temps were of the coolant at the heater hoses on both sides of the core to see if the coolant was actually passing through.

You could have had low coolant, an air pocket causing no flow if the air pocket locked up the heater flow.

Your coolant protection after 3 years may have dropped below its specs.

Some freak thing that will have to be caught when the failure occurs. Which means you may have to leave it overnight when the temps are expected to drop that low.

 

Thermostat was working. This isn't what I related. In 15 minutes engine would be at temp.

 

"Can't be thermostat or engine would have overheated."

IS what you related....

<shrug>

 

Didn't mean to jump just frustrated

 

Engine gets to temp, no warm air out of the heater. Have heat on the inlet hose but can't find the outlet to test (didn't look very hard).

This just started after we had our first hard freeze. Have not looked at it again.

Where is the hot water valve on this thing.

04 scab
5.4 l

 

F150 has no water valve. Is this the Heritage or new body style? First thing to check is the coolant level. Low coolant will cause no heat. Second check I would make is blend door... listen for a change in sound of air flow moving from hot to cold. Depends on the actual model where the actuator is located. If a new body style is this EATC, SEMI EATC, or manual heater control?

 

No wonder I couldn't find it.
New Body Style Lariat
Autoamtic control I guess it is EATC
Coolant level OK.
Change was not gradual.
will check for blend door sound
Thanks.

 

There is an updated blend door motor for some models.