discgolfdc

Hi, all.

Last winter, I noticed that I wasn't getting sufficient cabin heat in my 2007 Mustang V6 4.0L. In previous years, the heat kicked a**. Toasted you right up.

I've been trying to approach this systematically from a number of avenues. So far, this is what I've done (to no avail):

• Replaced water pump
• Replaced thermostat and thermostat housing
• Backflushed heater core (didn't perceive any difficulties with this - ran clear)
• Purged air from coolant system and vacuum-refilled
• Replaced temperature blend door actuator

I'm still not getting sufficient cabin heat, and it's starting to get colder outside!

The car gets to operating temperature and stays there perfectly. This vehicle has never once overheated.

I recently saw a video in which someone who holds himself out to be a Ford service technician recommended maintaining 3500 RPM in neutral for approximately a minute. This was for people who had recent cooling system repair work done but weren't sure that the system was bled/purged of air. The theory, I guess, is that it causes the water pump to push water harder through the heater core and, if there are any air pockets affecting the heater core, somehow this can force them out. I tried this last night, and, in my case, this does cause the heat to increase to near expected levels, but as the engine returns to idle, the heat dies down accordingly.

I decided to drain my antifreeze and vacuum purge the system today to be certain that I wasn't looking at air pockets. Unfortunately, after verifying that my system is airtight and refilling with fresh Zerex G-05 50/50, I'm still no better off. After the vacuum refill, the 3500 RPM thing does increase my heat output like before, though.

I also notice, sometimes, that when I'm driving, sometimes my heat increases a little bit when I'm engine braking. I don't know if this is of any consequence.

I'm hoping beyond hope that I'm not looking at a heater core replacement job, here, so my purpose for posting is to ask what other things, if any, I can reasonably check and replace if necessary before going there. I'm starting to get a little older now, so I no longer trust my own brain to have thought of everything.

I know it's a fairly simple system, but maybe there's something I didn't think of.

Thanks!