New Heater Core...Now I don't have ANY heat!

[84GNTTYPE]

About a month a ago I installed a new heater core because mine was spewing antifreeze on my windshield. It did still make heat though.

After I installed the new one, I didn't have any heat. The pipe going into the core was very hot, but the one coming out was not.

I pressurized the system and got some air out of it. Then both pipes were hot.

So, I reassembled it all and took it for a drive. Again, only the in pipe was hot. I pressurized it again and got more air out of it. But still only one pipe gets hot.

Do I have a bad core or is something else wrong.

I'd REALLY appreciate any help that you guys can give me, I don't know what else to do!!!

Thanks!

 

[Matt Weiser]

Could be your heat valve is bad/intermittent. This is the black plastic valve installed inline in one of the heater hoses, and probably has a vacuum line going to it. Could also be that your vacuum feed to the valve is bad. If the valve isn't working you won't get coolant flow through the heater core.

 

[84GNTTYPE]

The vaccum line going to the heater core is broke. I was told that the valve is in the open position when there is no vacuum to it.

Also, the pipe going into the core is hot, which leads me to believe that the coolant is getting through the valve.

Thanks!!!

 

[John Larkin]

I could be wrong but I think those only flow one direction. I've been led to believe that but it's been a long time since I replaced one so 1st hand knowledge is lacking. The valve should be on the pipe that is closest to the trans dipstick.

 

[bsdlinux]

Could possibly be air lock. Something to check anyway. Take the return hose off ( when the car is not running ) and make sure you can get coolant flow when the valve is open.

 

[84GNTTYPE]

Tonight I discovered that I have a leaking radiator. I'm sure that that is at least part of the problem. I'll get that fixed and then give the heater core another shot.

Thanks for all the help guys!

 

[REDS HOT AIR]

dont feel to bad i cant get no heat either

new heater core and no heater control valve

if i leave fan on low it put out hot air but if i turn the fan up it gets cold

full of water/coolant and pump is pumping cause moter dont get hot stays right above 160

has anyone tried restricting the bypass hose betwwen the intake and back of water pump since it takes away from the heater core flow??

 

[Matt Weiser]

I thought of another possibility. I swapped dashes this year and noticed there's a large flapper valve in the firewall that controls airflow to the interior. This valve is like a book-sized metal or plastic door with a rubber gasket around the edge. It's vacuum controlled, so that when you select your heating/AC setting, the door opens or closes a certain amount to regulate airflow into the car. I can hear mine slap open and closed sometimes when I'm working the controls. Could be that this door is stuck on your car, or maybe the vacuum feed to it is bad. Should be pretty accessible if you remove the glovebox.

I think there might also be a second, similar door inside the heater box, but I'm not positive about that.