I have a b18b swap in my 99 Civic with a stock radiator. I have the usually screw type clamps superman tight on the radiator. Friday I was driving and noticed I didnt have any heat and the temp gauge stayed in the middle...like it always does. I checked the coolant on saturday to find out I didnt have any. So this morning I bought a new thermostat and some coolant. Filled it with the cap off and heater on full blast. At first I could get the lower hose to heat up. Now that I got both hoses to heat up I still dont get hot air in the car. What could I check to see whats wrong....I already made sure the cable on the heater hose moves. I notice a rpm drop right when I start the car while it;s already warm....start it and it idles at around 1100 for about 10 seconds and drops to 8.

 

check to see if your car is leaking any coolant underneath the dash where the heater core is located...

 

nope...dry

 

check the temp of the hoses going in and out of the heater core.

 

Check the heater hose valve... http://cgi.ebay.com/ebaymotors/99-00...Q5fAccessories it is either disconnected or stuck closed. 94

 

Either you are leaking or burning coolant (hopefully leaking), you will probably want to bleed the cooling system if you haven't done so already