So its the first 34 degree morning and i needed some heat, low and behold it wasnt HOT, not even remotely warm!!! So, where do i begin to look, heater core? Last winter the heat was nice and toasty.

This morning it was idleing for a good 15 mins and then 5 min ride to school... NO HEAT!!! and im going to need it considering new england winters SUCKKKKKK

any ideas?

 

Thermostat might be stuck open. Does the engine warm up at a normal rate? Has your gas mileage been worse lately? Those would be indicators of a stuck open thermostat.

Also, check for vacuum lines that might be loose under the dash. If one is off, you may be stuck on cold instead of hot.

After that, the next suspect would be a clogged heater core. Does your coolant look clean?

 

well it seems to warm up normal... i dont how it wouldnt, it still runs fine, mileage is still the same about 12.5-13.5 i dont know were the vaccum lines are and last i heard the temp **** was cable driven

 

do both heater hoses coming though the firewall feel warm. guy i know had the same issue. mechanic said if only 1 is warm, whatever is inside (heater core?) is clogged. if none are warm, thermostat won't open (which i think you would know about). go feel both hoses going through the firewall.

(all based on my limited understanding of how this all works)

 

Most common problem is something fell down thru your defrost vent, and got stuck in the blend door. Door stuck open just a little will make a huge difference on the amount of heat you have in the cab.
I got to ask if you have used any form of stop leak in your cooling system? If so, your heater core is probably stopped up. Both hoses can be hot, and the core can be nearly completely stopped up.
Fortunately, replacing the hear core is very easy and cheap, and the steps are nearly the same as checking the blend door.
Remove the glove box.
Against the firewall there is a black plastic box with about 8 screws holding the cover in place. Take out the screws, and gently remove the cable for the heat control, and any wires or vacumn lines in the way. Lift off the plastic box cover and you are looking at the heater core.
In the lower left corner, you can see the blend door. If there is sometine stuck in it, like a 3 inch deck screw( don't ask), you can remove it and test the door to see if it opens and closes completely.
If the heater core is being replaced, just remove the two heater hoses from the engine compartment side. Mark which goes where to avoid a problem. Lift the heater core out and twist and turn until you work it out from under the dash. All the while dribbling antifreez on the old towels you laid in the floor to catch any spilage.
Reverse the process to replace the core. The core is just about $20 and the entire process only takes about 1/2 hour. If I was in your position, I would buy a heater core and have it ready in case I did not find the blend door stuck open. If the door is stuck, just remove the foreign object and return the heater core.
Good Luck Frank

 

good to know the core isnt that expensive, i was expecting upwards of 200 bucks.. guess not! i'll have to check it out, i have a feeling its the heater core, i used to get a water trickle noise more or less from the glove box when accelerating when its col, always told it was normal and is just the heater core.. something tells me its not normal and it needs replacing... is it possible im low on coolant as well?

and fmr, i can see how that deck screw got there lol... we'll see what happend

 

low coolant is a definet possiblity, happened to me once. I had the heater on blowing out the vents nice and toasty sitting at a red light on a hill and all of a sudden like someone turned on the a/c. filled it up and been good since

 

NPD has heater cores for your truck for 34.99.

I'd check the lines running into the firewall at temp, making sure to compare the two. If the core is plugged up enough to prevent heat getting into the cab, one hose should be cooler than the other.

Another possibility would be to remove the cover for the heater core box and see if the core itself is nice and hot. If not, I'd say new lines and core.

Check your coolant levels first of course. Not enough coolant means no circulation to the core.

 

low on coolant?

if you remove heater hoses mark locations first.

 

I had to replace my entire cooling system last winter because I let the heater core get clogged up and I had a slight leak in the radiator. I learned my lesson about flushing out the whole system periodically.

 

just took the truck for a good run on the highway, it started to get lukewarm, warm enough to feel good, when i stopped i popped the hood and felt the coolant lines. the ones that go to the firewall, the right one was WARMER than the left one(left is the one going to the engine under the intake)... heater core plugging?

 

sounds like it.

 

I 2nd the opinion you are probably mostly plugged. The heater core is cheap, but depending on what you have put in your cooling system, you may want to do a real good flush before you change the heater core. Be a shame to stop up a new heater core.
There are several brands of flush compound. I can't recommend any specific one, but I do like the little plastic valve Prestone sells as part of a flush kit. It goes in a heater hose, and lets you keep a garden hose connectd for prolonged power flushing. If you are going to flush it, better get with it before it gets cold. It really ain't no fun doing it in cold weather. Be careful. You don't want to let the cooling system build pressure and then pop the radiator cap off. I usually leave the cap on but not tight, so it can't build pressure while I'm waiting for it to warm up and the thermostate to open.
Good Luck Frank

 

hmmm, my 87 f-150 appears to do like yours, it gets warm but not real hot, i put in a new thermostat this summer, but it didnt change the temp. its a bitch. lol

 

i forgot to mention, but my temp. gauge stays normal all the time, just no real hot heat. bill