WAUKEENEM1

H/T...need your help again
bought a 99 civic ex with a leaking heater core...
Pulled one from a 98 civic but its a little thicker so wont fit into the 99 core box. So, i just swap the blend door actuator to the 98 heater core box.
Got everything put back together...started the car, let it runs for like 20 mins
Got up to normal operating temp but no hot heat just barely warm air ...check all hoses...no leaks or nothing
Check the actuator...it works too
Any ideas...??? Im thinking bad t-stat but both upper n lower rad hoses are hot.

sumdewd

Did you bleed the cooling system properly with the thermostat set to hot? Have you had your hands on the heater hoses to verify they're getting warm? Are all of your heater/air control cables hooked up? Certain civics will let you manually adjust the heater valve and blend doors, but the water valve and blend cable locations can be a pain to get to...

WAUKEENEM1

Oh...yeah for got to mention that the rad got a few pinhole leaks when i bought it...replaced the rad then noticed the heater core was leaking. So, i bypassed the heater core hoses until i can find a new heater core.
yes, all the the hvac plugs are plug in...even tried another heater controls.
the heater core hoses and rad hoeses are hot to the touch.
the 99-00 civic use an eletric actuator for the temp control which connect to the heater core check valve. I test it by turning temp to hot and cold and the actuator open n closes the check valve, i know it works.
I thought maybe its the t-stat but usually if thats bad or stuck then the lower rad hose would b cold...
Ill try bleeding the coolant

WAUKEENEM1

Bleed coolant...still no heat...
noticed the hose the connect check valve to heater core is somewhat kink...the bends are not smooth
will correct that so the bends are smoother...hopefully that will help a bit

tony_2018

check heater valve is opening

mk378

Used core? Did you flush it and check if it is clogged? And you're making a Frankenbuild, so have to check that all parts work together. The hot/cold control has to move both the air door and the water valve, in the correct directions.

As someone else said, a key test is to feel the heater hoses and see if they are hot. They should both be very hot, as hot as the bypass hose. You can't tell anything from the radiator hoses. If the gauge on the dash goes up to normal and stays there, the thermostat is OK.

tony_2018

Its "new to him", or whatever the term is.

WAUKEENEM1

Ok... so far ive bled the coolant, fixed the hose on the check valve that connects to the heater core so the bends are better now...manually open the check valve...
im pretty sure coolant are getting into the heater core...as the hoses are hot and full...
Car gets up to temp...and temp gauge stay at between hot and cold.
also both rad hoses are hot and feels full when sqeezed on it
Still no hot heat...
Should i just get the right heater core and put it back in the original heater core box?
im thinking of just replacing the t-stat?

WAUKEENEM1

Also the heater core i pulled is from a buddy's car...heat works great before i pulled it...so i know the heater core is good

JRCivic1

You already know that the '96-98 and '99-00 systems work differently... why on earth would you thank that swapping the blend box would work properly when one system operates mechanically and the other operates electronically ??? I suggest you use your original '99 blend box and order a replacement heater core instead of using the wrong stuff from your buddy... RockAuto has them for $50 or less.

WAUKEENEM1

Yes...i do realized that the 96-98 n 99-00 are different...thats why i swap the blend door actuator to the 98 box, it has all the mouting spot for the actuator...i tested and it works as far as open n closes the heater core check valve...unless for some reasons eventhough check valve open but the blend door is still close.
i guess, worst case, ill just get the 99-00 heater core n put back in the original box.

tony_2018

K, GL with that.