yeah i dont really drive the truck im trying to sell it but i have put new heatercore in it as it was bad then i put a new thermostat in but the truck its self will not heat up
covered whole grille up and still does not heat up gauge doesnt come off the C and you can tell the truck isnt heating up

 

First is the thermostat opening, are we sure it is closed, is the upper hose warm, If you take the cap off does it look like the coolant is flowing?

 

Enough coolant in the radiator? Faulty temp sender or broken gauge? They aren't known for reliability. Thermostat might not be opening.

The engine is heating up, there's no doubt about it...you can't run it and not have it create heat. How long have you driven it or idled it?

 

hah wow well i put the heatercore in and compaired them to my 89 and i have the hoses on assbackwards ...so is that the problem because the top hose is very hot when the truck has been running? im going to swap them tomorow afterschool....and yes the thermo is opening and closing properly i replaced it and we have checked it
i think its just the heatercore hoses?

 

The blend door is likely stuck halfway. The climate control is vacuum assisted.
The door is held to one side or other (heat or cold) by vacuum.
I would guess, a vacuum line is busted, or the vacuum reservoir is leaking.
There may be two reservoirs your truck. One is a coffee can on the pass fender, the other is embedded into the fan box. Trace all vacuum, and repair leaks
90 percent sure of this, if heater core and tstat OK.

 

well the climatecontrol thing was messed up on dads so he took cable off or something im not sure but made it to where u had to do sum underglovebox to change from hot to cold he did it on this but it did not change....im going to swap the hoses back in the right way tomorow see what happens im not putn money into the truck because well im selling it im not driving it but a little heat would help it snow in the winter time hah

 

The hoses don't matter much. If there's hot water circulating through the heater core you should have heat.

Is the fan working?

 

yes fan is working ...my dad suggested maybe if the hoses are backwards then for some reason maybe the temp gauge isnt getting a good reading.....btw this truck never ran above the n on the guage in the dead of summer but the heat absoulutly is freezing last year it was blastn then the heatercore leaked ever since i put a new one in i haave had troubles it is a good core no leaks....if it is "airlocked" how do i fix that? thanks for the help guys i appreciate it

 

Just driving it should purge it of any air.
Aside from the blend door the only other thing I can think of is that it is plugged up with leaves or other debris.

 

im kinda slow i guess tonight but what would be pluged up with leaves? not sayn your wrong by anymeans im just lost on this truck hah thanks again

 

I second the blend door. I had a little piece of busted off plastic in mine, i took it apart and cleaned it all out (found a pen down in there too!) and it was like i was driving a new truck again.

 

Quote:

im kinda slow i guess tonight but what would be pluged up with leaves? not sayn your wrong by anymeans im just lost on this truck hah thanks again

I think Jim meant that the heater box's air passages could be cloggled up. This "box" has the "blend door" in it that you also need to check, to make sure it's opening (or closing, depending upon how it's designed) when you call for heat. It's purpose is to shunt the fresh air through the heater core, and on into the cab, as opposed to NOT running the incoming air through the heat exchanger, in the summer, for example. By opening and/or closing off two alternatative passages, the blend door ensures that the heat in the engine-side of the heater box can get "exchanged" with the cabin-side air.

When you switch the hoses, make sure you can blow through the heater core, by blowing into one pipe, and confirming that it's exiting back through the other. Wear safety glasses, and you can use a short piece of hose to reach the heater core hose fittings. It's possible (though not too likely, IMO), that in the (re?)manufacturing process, the core became blocked by debris. But if you confirm blend door function, water pump flow proper coolant level, etc...then you have to start looking for the less likely causes. (You can confirm water pump flow by looking into the radiator neck, while the engine is running, as was mentioned above--and btw do this with the engine COLD, before it has a chance to pressurize the radiator, for SAFETY). You're just looking for a steady flow of water, out of the ends of the radiator tubes visible near the neck.

I'm joining the "blend door" contingent.

Good luck.

 

so where is the BLEND DOOR and how to i get to it?

 

I once had an '87 very similar to yours. As I recall to get to the blend door you remove the glove box then you can remove the heater cover. At this point you will probably be looking directly at the heater core, I think the blend door is up and to the left.

I bought my current truck with a pen stuck in the blend door, just could not warm the truck up.

 

so remove the heatercore again =\