Turboman

I was having the same issue as u did for 4 yrs. and finally I got that heater fix. I tried flushing the heater core, replacing thermostat, check the heater valve and finally I check the 2 cables that are connected to the heater control unit this year. Guess what, one of the cable was loose (still connected on both ends), so I tug on it and pour in some new collant and wah la......I got heater.....man, I was a happy man.........

I can live w/o AC, but no heater during the winter, that's just not going to cut it.......

Turboman

To answer your question directly. If there's no coolant leak inside the car, flush the heater core w/ a water hose to check the flow of water. If it flows smoothly and no leak inside the car, then it's somewhere else that's causing the issue.

SpankedYA!

Compressed air my blow it out.

crx2fast

instead of going through the hassle of taking the heater core out, you should just take the 2 hoses off from in the engine bay(the heater core house on the firewall) and just hook up a hose to one of the lines and see if water comes out the other line.... hey it beats takin out the dash, droppin the stearing colum yada.. yada.. yada.. just to find out that it might not even be your problem :P

91lsvtec

Yep, looks like I'm going to have to go with this option first.