Derek Roch

Ok guys i replaced my head gasket a while back and now my heater doesent work as good as it use to. The heater worked fine before the head work. When i did the head i also installed a ats exhaust manifold and i couldnt get the factory steel heater core line to fit so i ran rubber hose all the way from the heater core to the lower radiator hose where it goes in the block. I installed a petcock in that line in an effort to get any air that may be trapped in it out. But still nothing i have very little heat in the cab. So i dont know whats going on, I dont know if the rubber line that i ran has anything to do with my problems. Also does anyone know what way the water flows through the heater core does it flow from the head to the lower radiator hose or the other way around?

biododge1

The water inlet is the lower hose. You are drawing (if at all) cool water into the heater core.

Derek Roch

I dont guess I understand what you are trying to tell me. So the water passes through the heater core then returns back to the head next to the valve cover ?

RPegram

Try switching hoses around. If that doesn't work, check temp of water. If that doesn't work check blend door and such inside dash. You could've pulled vacuum line going inside and it is not opening door to allow heated air to circulate inside of cab.

kennyhammond

my truck is doing the same thing the only thing diff is i changed the thermostat (it was stuck open) and after that it has been coolair and not hot???? how or were is it located to check the door to circulate water in cab???? thaks

tmills

The line you ran should be going to the upper radiator hose, not lower. The lower is the cool side.
If you touch the heater line going to the heater core it should be hot to the touch, just like the upper radiator hose.
If your lines are warm then if could be a blend door problem in the A/C / Heater Core box. I would doubt this is your problem though since it worked before.

dodgeguy71

check and make sure you actually have flow through your heater core. Seen this many times on gm's. "customer complains no heat" find heater core blocked with sludge. Flush heater core and instant super heated cabin. Maybe not what it is but another check, also agree to make sure hoses are routed correctly.

madhat

Could be the water pump taking a poo, too...

kennyhammond

i would think that the truck would run hot if the water pump was going out and the temp on the truck is a strong 190-or so... but thanks for the sugestions

Copenhagenjunkie

That is possible in your hot weather, but you must of crossed the heater hoses. I had little to no heat after using some bars leak stop to get by when head gasket was leaking. All it did was plug the heater core, I back flushed multiple times over several weeks. Checked water pump and the fins were gone but engine temp was normal. Heater was still not good. Replaced oem water pump and back flushed heater core some more and now the heat is acceptable, it will keep the windshield from freezing up now! All this took place with over 300k miles. I did install a 12v heater on passenger side floor for the wifes feet.

kennyhammond

well all i did was change the thermostat so i know i didnt cross any hoses but i might need to flush the heater core or check that door thing... but other than that i dont know to much about the ac and heater

nickg

the heater core can become blocked, try unhooking the hoses, pour water in the core and blow it out with compressed air, if after doing this the air gets hot, then you will need to replace the core...or as in my case my fan "sounds" like its blowing hard, but I had little to no air flow thru the vents, hardly enough to keep the windows clear, and what I found was my evaporator core(inside the heater box was plugged solid) you can check it WITHOUT removing the heater box, just pull the fan motor out and feel around/look up inside to see that the evap core is clean, mine had about 200,000miles on it when I pulled it apart, since then I've gone another 100,000miles

kennyhammond

wow that looks great lol jk yeah i pulled my fan off (under the glove box and took a air hose and blew alot of dirt out of it but like i said i didnt know too much about that system so i didnt get into detail how hard was it to pull that piece out of your truck?