Heat Not Working In Front

[gmarchlewicz]

Hi all. I have a 99 expy XLT 5.4 4wd 105k with front & rear heat. I get perfect "Hot" heat out of the rear vents. The front vents blow cool. Fan is fine. As I adjust the front heat range from cool to hot, it only goes from cold to luke warm. The radiator is full. Reservoir is full. No major leaks, though I smell Antifreeze quite often when outside the truck. I just added a tube of bar's stop leak last week just to be on the safe side. Still smell antifreeze but dont see leaks. The engine temp runs right in the middle with no "Spikes" and drops. So, i'd say the thermostat is Ok. Any ideas on why the front heat isn't warm?

Thanks!

 

[Catatonic]

blend door.

 

[JUST4FUN]

Warm up the truck find the heater hoses that go to the fire wall put your hand on both of them and see if they are hot in and out make sure the fan is on high, and the heat is on full

 

[rthunstrom]

check the blend door motor, actuator, and blend door itself.

 

[RedRanger91XLT]

the front and rear ventilation system in the expy are seperate. there might be something wrong with your selector...

 

[gmarchlewicz]

Thanks for the advice.

I ran it up to normal operating temp. Ran the heat for 15 mins front and back. Felt both hoses going through fire wall. Right one was hot. Left one was cold. Seems to be a clog in the heater core. My interior is bone dry and theres no coolant smell in the cab. I'll try flushing it tomorrow. Ill probably have to replace the darn thing. Any other thoughts?

 

[RedRanger91XLT]

make sure you have coolant in the heater core.

 

[JUST4FUN]

This is how i fixed my wifes heater core Take the heater hoses off the engine.
Next I used a pressure washer (with the nozzel off) to clean it out. go both directions

 

[gmarchlewicz]

Well, it's fine now. I didn't do anything. Woke up this morning, turned on the heat, and both hoses going through the firewall are hot now. The heater core is unclogged. I think maybe the Bar's radiator stop leak did it? I should flush my system. I have had the truck for almost a year and it hasn't been flushed yet. It's the only fluid besides my brake fluid (That can wait for a brake job) that hasn't been changed yet. I picked up the Prestone flush kit where you cut the hose and put their insert (That you run your garden hose to) between the two cut pieces of hose. Anybody ever use this method of flushing? Would a shop that does flushes have a better way of doing it? I have a crap driveway (Due to be replaced in the spring) that I can do this on so no worries there. Of course I'd drain the antifreeze first.

So, anybody ever do a flush themselves? Having the dual heater cores, I'm wondering the placement of the Prestone "T"?

Thanks for all the suggestions. BTW, I love this truck. These expeditions are awesome for just about anything you want them to do.