I finally got my 94 Civic EX up and running again. The car has a JDM b18c and the car runs/drives great, but I dont have any heat at all. Ive triple and quadrupple checked that the slide valve to the heater core is indeed open. I even pulled the cable off of it and left it open. Car is up to temp and thermostate opens up, but both hoses to and from the heater core never get hot like the radiator hoses do. The heat worked fine with the D16z6 in there so that rules out a clogged core. The engine temp stays constant with the needle just below half way up.
The hose from the slide valve on the firewall runs to the front of the head near the distributor and the other hose connects to the hard pipe under the intake manifold.

Any idea's? Please help its getting really freaking cold here in the midwest.

 

the water port on the intake go's in then it comes out the valve and go's in the water port on side of the head

 

Well then the hoses are hooked up correctly, but still no heat. WTF?

 

is there water coming out the two hoses?

 

No water is flowing through either one. They never get warm, even when the car is up to temp.
The heat worked fine with the D16 in there, and the hoses spilled plenty of coolant when I originally disconnected them so that leads me to believe the core is ok. Could a bad water pump cause this problem even though the temp gauge holds steady?

 

do water come out the two ports on the head when you unhook the hoses?

if the water pump was bad it will over heat

 

Ill have to check it tonight when I get home. Someone also suggested that the heater core could be air locked. They said to let the car warm up and just crack the lower radiator hose to see if that will cause coolant to flow.

Ill try em both and let you know. Thanks for the help.

 

or there is something in heater core blocking the water

 

Well I started the car up again and let it warm up. T-stat opened up and BOTH hoses going to the heater core are getting warm, so coolant is flowing through, but it is still blowing cold air out of the vents. What gives?

 

take the heater hoses off and take a hose pipe and shoot water in the heater core to make sure water is going in it and out it

and make sure its blowing fresh air

 

Alright, I did all that. Also ran some of that Prestone cleaner/flush through it and nothing, same problem. Some one suggested the hot air door could be stuck or disconnected. Where under the dash would this be located at?

 

could be.. did you check the blower motor to see if its workin properly?

 

Yeah its cold out. But if youre saying the hoses get warm, and its not blowing warm out of the vents, then cancel out the engine bay. Did you look under the dash and feel the pipes going of the heater core to see if they are warm? Did you check the coolant pressure and cap? Did you happen to disconnect anything (by chance if you happened to) in the cabin related to the blower or mode control motor (controls the doors/vents and its plug is behind the lower cover with the ash tray)? can you HEAR the blower motor or the doors move when you press the FRESH or RECIRCULATE buttons? Also did you bleed the cooling system? Since you did a swap, you left the lines open. May have some small or huge air bubble(s) caught in there somewhere that need to be expelled. Just throwing ideas out there