Hello, I'm new here with a '97 4.6 pushing 170k.

My most recent problem is that I don't have much heat. It takes the truck a good 20 minutes to even get a noticeable amount of warmth from the vents.
Even after I'm driving awhile, it only feels as hot as some stinky breath.

I believe I've ruled out the blend door issue, as I discovered it seemingly working well hidden atop the tranny hump. I'd say it's getting roughly 90 or so degrees of "actuation" through it's rotation, which I believe is suffice enough to allow the door the fully open and close.

Also, I've got a code reader hooked up to the truck, and it's able to tell me the coolant temp which is only peaking at 175ish. At first, someone suggested it might be a bad coolant temp sensor, BUT If I can watch the temp rise via the reader, shouldn't that mean that sensor is working?
But I don't understand why I'm only reaching 175 degrees. I replaced the thermostat thinking it was stuck open, but that didn't change anything.

The temp gauge also only goes up barely half way.

I'm told 175 degrees is hot enough to blast some serious heat, but right now it feels as if it's only 50-60% of what it could be.

I thought maybe the heater core is bad or plugged as I've noticed in the forums. But I don't have any leaks, anywhere.

Plus, the heater core hoses going into the firewall are pretty freakin' hot after the truck "warms up".

I can't think of anything else at this point. Maybe some trapped air in my coolant lines? But why only 175 and not 215 degrees?

I'm kind of stuck at this point.
You guys are great and any enlightenment would be much appreciated!!!


Thanks,
Jay

 

If BOTH heater hoses are 175°, then it means the AIR thru the heater core is blocked. Either by lint/leaves/debris or by a diverter door not swinging all the way.

If only one hose is hot, then the heat is going somewhere inside the dash - just not where you want it.

If neither is as hot as the radiator, it means there's little or no coolant flowing thru the core.

 

has anyone ever put a heater core in it before i know if you put the heater core hoses on backwards you wont have any heat i have seen that done

 

you dont have to have a leak for the core to be plugged. take of the heater hoses, grab a garden hose and blast all the junk out of there. at 170k i suspect lots of junk will come out.keep flushing until water runs clear. had the same problem on my dakota,flushed it and the heat came out like a blast furnace.

 

I think I have this problem.... heater only puts out "luke warm" heat. I warmed up the truck and both hoses appear hot. I have no idea where to try and clean out any debris. And what/where is this diverter door you speak of? ( 2004 F150 Lariat 4x4 screw 38000 mi. )

The air will blow where ever I select with no problem... Its just not warm/hot....

Please be gentle...

Thanks,
2 cold infants and a wife = very miserable dad...

 

It's the door inside the ventilation ducts that DIVERTs the air to the register you want it to come from. But you say that's working.

So back to the blend door: have you checked that the actual DOOR is moving the full 90°, or are you only looking at the lever outside the case? The doors have been known to break away from the lever.

 

I have no idea how to check the blend door.

I've been messing with this a little more today. About 3+ hours ago I tried to see if I had the infamous cab filter, which it doesn't appear so. Also verified which hoses were hot.... (both were hot) At that time, luke warm was the best I could get from the vents.... which is what happens 95+% of the time.

I go out there 10 min. ago, let her run for a few... and boy is she giving me some warm/hot air.... earlier the outside temp. was in the 30's, now its in the 40's... odd coincidence? This time I also turned the AC on as low as it would go, trying to hear the "thump" of some "vent" closing?... Turned back to heat and whatdayaknow, it starts working. (Never did hear the "thump")

This help with diagnosis? blend door? heater core? clog? other?

 

Hey everyone, thanks for the insight.

I had never realized that debris could cause this problem, because the blower has good strength, but now I understand.

As for the blend door, I'm like 90% on that. I can listen to the door move. It goes from completely cold to what is my hot setting.

I would say the heater hoses going into the firewall are about the same temp, at least not a difference I could distinguish.

For cleaning the debris out, how would I go about that? I think a few people wonder that? Do I need to remove the screen below the windshield and get down in there?

I'm going to clean it out later today. I'll try and take some pictures for any of you who are curious.

Wish me luck!
Thanks again all,
Jay

 

if you are talking about the heater core, just take of the hoses at the firewall and flush it out with the hose.

 

I understand how I would need to flush the core itself, internally.

But if the fins themselves are clogged with debris, then how would I go about fixing that (without removing it)?

Doesn't the heater core circulate it's air from the grill below the windsheild, and from inside the cabin? Once it was mentioned that debris could be the culprit, I right away remembered how the truck sat under a pine tree for two years with the previous owner...

So, I plan to flush it internally through the hoses and somehow try to remove that grill and find what has fallen in there over the years.

Til next time...

`Jay

 

Magic.