heater not working

[boxerjl2]

Yes the truck stays at 190 once heated..

Ill get pics of the engine bay

[boxerjl2]

Here it is.. this is how it was hooked up when I bought it

Bottom hose is hooked to water pump and top hose is hooked to the intake manifold

[Irish_Alley]

ok maybe its just my set up but i have the pressure side your top hose in the intake and that looks right but the return is hooked up to the rad right underneath the over flow

[Irish_Alley]

ok after looking it up it seams it can go either way. but the top is supply and the bottom is suction so in theory you can have a air bubble get trapped in the core

[boxerjl2]

Ok so the water pump shud be hooked to the top

[boxerjl2]

I probably mixed up the hoses when I replaced the water pump last summer
Would explain why it worked perfect last winter

[bd]

Ok so the water pump shud be hooked to the top

I probably mixed up the hoses when I replaced the water pump last summer
Would explain why it worked perfect last winter

The heater supply exits the 5/8" bib in the intake and returns through the 3/4" bib in the water pump.  The heater core similarly has 5/8" In and 3/4" Out bibs.  Connect the hoses accordingly.

[boxerjl2]

Ill have to check that out thank you for your help

[boxerjl2]

As far as I can tell from what u said the intake bib is the supply and the top of core is supply so I have it hooked up correctly from what u said

[Irish_Alley]

yes, the water pump bib and (if you had one) the rad bib are the same size and both are return. if you had the one in the rad you could just look into the rad and see how well it was flowing. i also want to say (just me thinking bd or someone verify) but some water pumps also have ports on the driver's side these would be supply's and the ones on the passengers side are returns

[boxerjl2]

This water pump only has one bib that I can see.. I still don't understand. Why its only working with cap off.. cud I have too much coolant?

[Greybeard]

to me,  that makes no sense. I can't think of any reason why the cap would cause the coolant to stop circulating through the core. Your hose bib on the radiator is not in the neck is it? Shouldn't be.

[Irish_Alley]

the only thing i can think of is the cap allows pressure to build up in the core restricting flow threw the core. the only thing i can think about that would cause a restriction would be air. try reversing the connections on the heater core. like put the water pump (return) to the upper connection (supply) in my head this would force anything (air) up and out. its easier to get air to go up then down.

[75_chevy]

you said both heater hoses are hot to the touch which would mean the hot coolant is passing through the heater core if I'm not mistaken. could it be your switch in the cab is set to cold and not hot? also making sure ur switches work, from how my truck works you slide the switch over and it moves a flap in the heater allowing hot air to pass through from the fan blowing through the heater core. when you slide your switch over can you hear the flaps moving? maybe they broke in the "cold" position


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[Greybeard]

Irish.. yes the hoses are hot the heater works but only when the radiator cap is off.. and. Not sure about the thermostat.. I just got a normal 9ne from what I know Idk what a failsafe one is

And thanks for the info grey but my cables are working the glovebox is still off from the heater core change and can see them working

My heater wasn't working so I googled it and that's when I burped the coolant and my heater was blowing super warm so I put the cap back on and drove about a block and then it was just blowing air

OK, you see the cables working, that doesn't necessarily mean they moving what they are attached to. There is a small valve that controls the coolant flow through the core this is easy to see if it's still there, the flap door inside the dash may be a bit tougher to but a flashlight helps there. The cooling/heater systems on these old trucks are about as simple as it gets when there is no A/C to deal with.

It still makes no sense why it would warm up with the cap off and not on. The cap has no bearing on the way the coolant circulates. All it does is keep the pressure in the system to raise the boiling point.

I still suggest draining about half the fluid out and disconnecting both hoses to the core at the engine and using garden hose pressure (unless you have 60psi water pressure that is) and blow water through it from both directions. Start with a slow stream to see if it is open, then keep increasing the pressure to see if there is a point where it doesn't want to let as much out as there is going in. Be careful and don't over pressurize because they (the core) are only capable of handling about 20psi. The r/cap should be about 14 psi. Some are as low as 7 psi. If a good solid  stream is flowing (not shooting!) out the end about three inches then it's good to go. It needs to fill the hose diameter with the hose nearly level or below the point of attachment to the core.

However, if this pans out it has to be inside the ductwork. Pull the fan out and see if the face of the coil isn't plugged with crud. Pull the coil off and look and make doubly certain the doors are all opening and closing completely. On my truck they make a solid thunking noise in both directions as they move overcenter. One other question...it wasn't at one time a truck cab that had a/c was it? If so there is a air valve on the passenger side where non-a/c trucks usually have a manual vent. If you have the manual vent nothing to worry about. Otherwise, if that fresh-air-bypass valve is open it lets cold air in from the outside, it's supposed to close (or open, I don't remember which) with vacuum in concert with the a/c or heat (again...don't remember which).