NEED HELP Reverse Coolant Flush?

[RyanEAS]

I've got an 04 TB EXT. I'm having issues with the rear heat (or lack thereof...). It's only blowing cold air. From my research on here and that "other" forum, it's either the rear heater core or I need to install the auxiliary heater pump that they suggest in the TSB. Before I go ahead and replace the heater core and/or install the heater pump, the dealer suggested I do a REVERSE coolant flush to clear out any blockage. Fine by me! Only one problem, I have no idea how to go about doing that. Haven't found any vids on youtube or anything else that would help me with this. Anyone got any pro-tips on this? Thanks in advance!

 

[Sparky]

Not really heard of that personally.

 

[Blckshdw]

Are you sure it's just not the rear temp actuator that's dead, and in need of a replacement? If you have someone sit up front change the temp controls, can you hear it moving if you sit in the 3rd row seats?

 

[Mooseman]

Can you feel hot coolant going to the rear core? Just behind the rear wheel, you should see the lines going up into the rear HVAC. If not, the coolant diverter valve may be stuck closed. It's located just below the right firewall. Just follow the vacuum line.

 

[RyanEAS]

I guess I should have provided a bit more info...
The coolant diverter valve (aka Heater control valve) i personally replaced this past spring (let me tell ya, that was a bitch of a repair)! I also felt the coolant lines under the car on the passenger side that lead to the core, and one is hot and one stays cool, which is why I was thinking it was a blockage. I didnt think about the actuators, I'll look into those. I did replace one of the actuators a year ago that was doing that annoying clicking on engine startup.

 

[linneje]

I agree completely with the actuator being the likely culprit. Having had a vehicle with poor heat because of a clogged heater core, the air that blows is lukewarm and you can definitely tell it apart from cold. I have also had the rear actuator go in the trailvoy, and that air is the definitely cold, not lukewarm. If the air is cold, as you describe, the actuator is at least the place to start.

If you remove the rear passenger interior molding, it is possible to remove the actuator and rotate the blend door by hand to see if the blend door is in the correct position to blow heat.