Yes, you are checking to make sure the blend door is moving freely and not allowing other air to mix in with your "hot" air (which may be causing your half warm heat)

Yes, the heater core is located in the top of the air mix box, above the blend door itself.



I had my heater core leak about a month ago and I have been tearing it down and working on the car ever since. I have been doing other things as well as the HVAC stuff but it still takes a little time.

 

i would suggest replacing the radiator coolant with water then turn knob to full heat and then start the car. rev it high will in operating temperature. that should help to remove the gunk. then drain the radiator again and fill with the correct coolant.

 

Andrew,

I already flushed the heater core with a hose, both normal flow and reverse flow. I even used compressed air to get some of the gunk out. I'm not sure how much that would help. I almost feel like it's worth it to just simply replace the heater core and be done with it.

I have another car I can drive daily. I figure if I start doing a little bit after work each day, I should be able to finish this job in a few weeks. Does that sound like a reasonable time frame? My A/C is already evacuated, I've become a pro at draining the coolant from the system and this won't be my first dash removal (not on an Evo though). Is there something complicated regarding removing the HVAC box or the heater core itself?

 

There isn't anything particularly complicated. If you have the coolant drained and A/C evac'd I would just go ahead and pull the mix box. It will be easier to work with.

There are a few nuances as far as going back in with all the components but not in the removal.

Holler if you need help.

 

I'm having this same issue in my 2006 Evo.

Any updates on heater core replacement?

 

Figured mine out, it was a bent/kinked coolant line running into the heater core on the engine bay side. I just had to un-twist it and walla.

 

Relentless, I've seen situations where the heat will get hotter when you give it some RPM; I bled out air and topped off the coolant system and it was good after that.

 

Just to update everyone. I decided replacing the heater core in the middle of January did not sound like fun. So I took the car to AMS in Maryland. They informed me that after dismantling the dash that they would be repairing blend door box (they said it appeared to be binding slightly), They then put the car back together and....still not fixed. They said the air got hotter, but still not where it should be. So, they are taking the dash apart again to replace the heater core. We'll see if this fixes my heat problem. Wish me luck...

 

Why didn't they just replace the heater core as well when they had the whole dash apart the first time??

 

After they pulled the dash they saw the binding blend door and assumed that's what was causing the issue. Now, to be fair, they did make the situation right. They are replacing the heater core for free. So, I can't complain at all. They've been great to work with and have been nothing but nice the entire time. So, my hats off to AMS. I just hope this gets my heat back to where it should be.

 

Final Update: After the shop replaced the heater core, I have full heat! FINALLY! The rest of the work AMS did on the car is top notch and I couldn't be happier with my Evo.