Hi Guys,

I did a lot of searching for my problem but didn't find anything specific to my problem. I have lots of ideas but I'm trying narrow it down to save myself a lot of work.
I have a 99 F150 4.6 4wd. My heater blows luke warm air even after the truck comes up to normal operating temp. I'm not losing any antifreeze anywhere. The temp control **** is not cracked and is turned all the way to hot. I can turn it to cooler and it does cool the temp, so it seems to be working. Is it blocked and won't go to high temp? I replaced the thermostat tonight and it didn't help. Coollant level is not low. The upper radiator hose gets good and hot. The heater core hoses are hot as well. One is hotter than the other though.
Could my heater core be plugged? I haven't added any stop leak or anything to the coolant though. I've been reading about the blend door as well. Could it be that or a vacume leak? Where do I check for a vacume leak? Any ideas on where to start would be very much appreciated it's getting cold in Wisconsin. I'm really hoping to be able to determine the problem before I pull the dash for no reason. Is there a way to trouble shoot this and possibly fix without pulling the dash? The more I search the more confused I get.

Thanks a lot for your help
Ganz

 

If you jump on the hwy will the temp of the heater go up?
I have trouble with my 98 warming up in cold weather. It is a desert truck with the large core rad. It runs about 150 around town and just hits 180 on the hwy below 35 deg. (aftermarket gauge) I remove the clutch fan in real cold days so I will have good defrost and heat. Oh, I have a 195 stat and the clutch fan works fine.
If you think yours is a similar problem, you can block off part of the rad to see if it gets better heat.

 

After talking with some people I'm starting to think that my heater core may be partially blocked. With the fan on low I get decent heat if I turn the fan to high it gradually cools down. What do you think?

 

bad or restricted heater core.

 

Ya that's what I thought. I'm going to try to back flush it. Is there any additive you can put in the antifreeze to clean it out instead of back flushing it? I really hope it's not the core. I hope it can be cleaned out. I don't want to pull the dash.