87 5.0 w/AC

Hey; My heater isn't putting out any hot air, only cold. I've changed the heater core (and it looks like the previous owner did the same within the last year or so) to one from LMC. Core gets hot and is definitely fine.

I've checked the temp blend door and it's working fine. I'm thinking maybe that the new heater core isn't as big and that air is going mostly around it. Is this a common problem with the repro cores? I'm out of ideas at this point. Thanks for any input.

 

have you measured the temperature at the vent on heat and off? if the core is heating up, and the air is actually blowing across it, it will register a change in temp, even if it's a small one... if there is no change in temperature, the are is not going across the core.

 

I havn't actually measured it, but it seems to 'take the edge off.' Not even enough to warm your hands up but I think it's warming a tiny bit.

I think my next plan is to stuff a bunch of paper towels all around the heater core and make a jerry-rig seal. Just enough to be sure air can't bypass it and get the heater box cover back on.

 

sounds like a good idea.

 

I have an 87 I6 and the only heater core that worked for me was a factory replacement from my local dealership

 

X2 to above post. If the core doesn't fit the box properly, you're going to be cold.

 

hhmmm, no bueno. Youd think this issue'd be dealt with. Out of curiosity are there differing heater box designs? At any rate I'll try stuffing junk in there tonight to close the gaps. If it works then the TIG machine and I have some work to do. Thanks for the input guys.

 

Yes there are two different heater cores one is a standard output the other is a high output they look totaly different.