Hello everyone,

So when I bought my truck the radiator leaked. So, I have since replaced the radiator, put in a Ford thermostat, and put fresh 50/50 in. I'm having trouble with the heat now.

First, it only gets slightly warm, almost not warm at all. And then while your driving it will randomly go to being cold air basically ambient (it's cold out). Also the temp guage will go up to like the "m" and the fall back down, it seems to fluctuate a bit. Even when it's reading higher the heat does not warm up.

The heater core has one hose that's very hot but the other is only kinda warm. Does that mean it's clogged? Should I try flushing it out?

I checked out the blend door today, I removed a pen and a pencil from it and it removed some of the notchiness in the temp switch. It still does not completely close and allows cold air in. Does that mean something is still blocking it or is it supposed to not close all the way?

I appreciate any input, it's too cold to be driving with no heat!

 

Yea, both hoses should be hot.....Is there a valve on one of the hoses?

 

Nope, I believe they are both straight shots, no valves.

 

So I'm going to just replace the heater core tomorrow. I'm still curious to know if the blend door should completely seal, and if I am unable to get it to close can I seal it off in the hot position?

 

I would just get a water hose and try to blow it out first....For the issue with the cold air passing through. They do not make a air tight seal, "but should be touching when closed." There also should be a thin layer of fiber like weatherstripping between them.

 

you can try reverse flushing the core, but it is at best a temp fix.
when you have the heater core out, reach inside the plenum and make sure everything is clean in there before putting the new core in.
my bet is there is still something blocking the blend door.

 

Is there one blend door or two? I could only see one door moving?

 

2 doors. one determines heat or ac/vent, the other determines defrost/vent/floor.
normally it is the door between ac/vent and heat that gets jammed partly open that causes no heat/ not much heat conditions.

 

Picked up the new heater core from Napa today. I have new hoses for it as well and some radiator flush stuff. I'm going to flush the system since the fluid looks pretty nasty still. It was bad when I first drained it to do the radiator, lots of rusty water.

 

Alright, I've got heat that will melt your face!

Started by flushing the cooling system for the 2ND time. Then I was able to remove another pencil from the blend door once I had the heater core out. I went ahead and still replaced the core, black fluid came out of it when I dumped it out. Installed the new core, put everything back together, filled up with antifreeze and distilled water and it works flawlessly!

Don't know if doing just the blend door would have fixed it but it was cheap to put a new one in.

Thanks everyone!

 

no problem. glad you got it back in proper order.
when you consider the fact you are messing with a 17+ year old core, replacing it is just good insurance that it will not start leaking next week.

 

Yes, I think it was good to do regardless. Knowing my luck, it would be leakin tomorrow if I didn't replace it!