i just dropped a b20 vtec setup in a civic 4 door it came out of my integra.... ran fine in the integra and just dropped straight into the 4 door and it has only cold air blowing from what should be the heater and over heats like no other.... wtf?

 

sounds to me like you need a new thermostat, but not enough information to really know.

Check coolant, coolant is full, and you're overheating, id check the thermostat, if the thermostat is good, water pump possibly.

 

Stupid question, but did you fill up the coolant? If so, HOW did you do it? With the heat all the way up? Car on a level surface? Did you wait two fan cycles before driving?

 

BUMP bc I am having the exact same issue.
it will run great for hours, then outta no where, over heat and no hot air,
then mins later everything goes back to normal.....
help!!!!!!!!!!

 

All you guys have AIR POCKETS. When you filled your cooling system up your car wasn't sitting on level ground (or with the front of the car slightly higher), your heat wasn't cranked up, and/or you didn't wait two fan cycles before you called it a day.

 

thats what I am thinking also.
I understand how air pockets would cause this.
but if the thermo was sticking or we would that also cause this?
bc like said before it seems that when it would over heat is when it would blow cold air.
I guess I am not familiar enough with cooling systems to understand how that would work.

 

if there is not warm/hot air coming from vents then check the valve that is controlled by the switch to see if it came unhooked.
the valve should be located near the firewall, literally in the middle section of it!

 

Check coolant leval and bleed your coolant system

 

there is no thermostat in the car, the heater doesnt work period. the car was on a level surface with the heater on when i filled it up, just replaced the head gasket too because there was some oil/coolant mixture.. got that together and realized my head it warped. so i have to have it surfaced. do you think the head being warped could be the problem?