Hi all!
Recently acquired 2006 GX (200k miles) with an annoying heating issue, hoping for some help from the experts here .

When I got the truck it had no heat at all, I checked the coolant level first and it was ok (green coolant). The car had no pressure (soft upper hose) and the inlet hose of the heater core was warm but outlet was cold. I swapped the thermostat which cured the pressure, I replaced the cap for good measure. I then flushed the heater core (garden hose) which pulled some gunk out and I got some heat from the drivers side, it quickly however dissipated. I decided to again flush the core (garden hose), more crap came out, heat was better on drivers side but not great, intermittent but again only drivers side. I decided to check the actuators on the passenger side. I ran the diagnostics on the head unit and no codes, I did notice the actuator that moved when adjusting temp (pass side) was moving very jerky and I was unsure if it was completely closing the door. I decided to remove it so I could operate the door manually. Still no heat. I went for a third longer flush using prestone radiator flush mixed with water. I circulated it in each direction for about 45 mins (submersible pump recirculating into a 5 gal bucket), some more stuff came out but I could not tell just how much. The drivers side seemed hot (I should have recorded the temps) but the passenger side still no heat. I also noticed that if I close the passenger vent the temp on the drivers side vent (above radio) gets much cooler. So now I have a few questions

• Can anyone tell me what each actuator does on the passenger side? Am I correct to assume that the actuator that moves when I move the passenger temp does indeed control the air that passes over the heater core? I want to 100% rule out any possible blend door issues (I did not mess with the drivers side at all).
• I am suspecting a partial block in the heater core, maybe a more aggressive and longer flush using CLR? I wish I could feel or get a temp reading on the passenger side of the core, is there any way to get to it? I thought about maybe drilling a hole in the housing I could later plug to be sure the core is getting hot on the passenger side.

I want to sort out the heat issue before I get too far into any repairs. Replacing the heater core is nothing I want to do on this car. Its a cool truck but it also needs tires, a PS pump, and probably a timing belt as I have no receipt of one done recently so I can quickly get up there in repairs/maint.

Any other help/guidance is welcome! And Thanks!

 

There's only one heater core at the front. For reference, the rear is A/C only.

I've never had one out, here's a diagram for your 2006 (different p/n than 2003-2005)

https://www.mylparts.com/v-2006-lexu...ter-components

My guess is that:
#19 controls airflow direction on the passenger side.
#10 controls fresh/recirc
#11 controls heat/cool - from what I know, the heater core is hot all the time, and this door is what allows air to pass through it when demanded.
#9 controls airflow direction on the driver side

(total guesses going by where they are and their names)

Having the wrong coolant in there, and that you're getting gunk out when running fresh water through it, would indicate a blocked core. HOWEVER since you're getting heat out one side, that would indicate a door motor. There's no driver/passenger side on the core itself.

Chip H.

 

Thanks Chip,
Yeah I have studied that diagram a bit.
#19 is the recirc servo, in my case I can easily see it working fine. The one I suspected was bad is #10 (front air mix) I was able to see that moving when I adjusted the passenger side temp. I assume there is a similar one on the drivers side. The drivers climate control seems to be working.

I wish I could feel the core on the passenger side or shoot it with a temp gun. My hunch is still a partially blocked core, if I look at the diagram the hot coolant enters the core at the bottom on the drivers side. So any sediment could be pushed towards the passenger side thus blocking the core passages on that side, again a guess without knowing if the core is hot on that side. When I feel both the inlet and outlet tubes inside the car they are both hot so hot colloant is definitely making it through at least some part of the core. I think I will try another longer flush and hope for the best.

 

As a follow up I again (4th time) flushed the core using a home made setup consisting of a 5 gal bucket, 2 lengths of 5/8 tubing, a submersible pump, and an old sock to act as a filter for the output. I added 3 small containers of CLR this time (lots of info on the web on whether this will hard the aluminum or not - I couldn't see how but I guess use your own judgement. My setup ran for 1.5 hours mostly pushing the solution backwards through the core ( I did reverse it for about 15 mins in the middle).

The 3rd time was using a prestone flush product mixed with water - I got very little particles out and no difference in heat.
The 4th time (CLR) I pulled another significant amount of debris and I now am getting passenger heat. I suspect there is still more in there as I get about 140 degrees neat the radio and about 120 at far passenger vent) but this is good enough for me.

Maybe this will help someone else.

 

Glad you got it unblocked. Doing some research, people seem to think that white vinegar is safer, as it's a weaker acid.

Be sure to run lots of fresh water through to get all the CLR out. And then fill with Toyota long-life coolant (pink in color).

Chip H.

 

Sounds like a stubborn blockage that you've finally gotten to break up and move, good job! Perseverance paid off!

X2 making sure you get all the CLR flushed out of there.