I just changed the heater core on my 99 F150. What a pain!. ran fine, now after 3 days, i do not have heat. Bottom hose is cold. What do you guys think?

 

Do you have the regulator? If your coolant full?

 

Air in the system maybe around the thermostat not allowing it to operate and open at the right temp. Or bad thermostat. Did you do a full coolant drain before the core replacement? And during the fill, wait for it to get to operating temps before purging the system and topping it off.

 

no. Just changed the core. What to do now?

 

Soudns like a bad thermastat how the temp neelde on the dash?

 

Thermostat or air in the lines. Id change the thermostat anyways, but I change mine every year because I have OCD.

 

Like mcolford said, change the thermostat for good measure, and then follow the procedure below to "burp" the system.

Run the engine with the heater on high (very important) until the radiator fan cycles. Then shut it down and add anti-freeze as needed. Then bring it back up to temp(fan cycles) and double check the coolant level as a precaution.

 

 

thanks, we'll try that. it gets heat then no heat. then heat and then no.
the needle is not moving, so probably not the Temp. it gets to a medium range and stays.
Someone said to put the truck on a hill with it's nose in the air and run it until it burbs.

 

Try it, - has to be warm and circulating. Degas bottle has to be higher than the core.
Just keep in mind, running it like that creates hot spots thru the heads. They can warp/crack that way.

 

Also, they only like 192's and 194's as far as stats. Not sure exactly why, but I've had trouble with others.

 

bled the system , changed the thermostat, but still heat for a few days and then cold, then heat again, then cold.
any other suggestions?

 

Water Pump?

Impellers rotted away?

Just an outward suggestion, not saying it is this.

 

I know the threads a year old but I think that's the problem I am having.
Thermostat replaced, system flushed, still no heat. I'm at the point that
the only thing left is the water pump. Could it be worn enough to cool the engine but not push water up to the heater core? The pump's got 270K on it with no leaks or noise or overheating just no heat.

Mike

 

Did any one find and answer to the no heat problem? I have a 99' with the 4.6 and am at my wits end as to what to do next. I have replaced thermostat (changed to a hotter one), changed water pump, flushed system 3 to 4 times, heater core has been burped and has proper flow (just no heat). Checked the blend door, actuator motor, replaced temp. control, checked vacuum lines (used vacuum tester inside the cab and under the hood). Top heater hose from radiator checks at 110 degrees after 40 mile trip and bottom runs around 88 degree. When you park after a trip you can touch the block and hoses without being burned. The block will not heat up. I am at my wits end with this truck I even went as far as putting cardboard in front of the radiator to check the fan clutch and it still runs cold! Please, any ideas welcome!!