[99SC4Runner]

I just got this 4Runner and I just replaced the radiator and thermostat with brand new ones. I have 182° at the upper radiator hose and around 160° at the lower radiator hose.

My heater valve is working correctly and with my infrared thermometer, when the engine fully warmed up and heater blower on High, I have 182° going through the heater valve on both sides and into the heater core. The temp coming out of the heater core (far right tube) is 148° which means that the heater core is exchanging the heat through it. My heater temp knob works normal with no issues, and it's moving the heater valve cable and the cable that goes to the white plastic linkages on the bottom of the HVAC box.

My air outlet control works because I have defrost, vent, bi-level, and floor air with the movement of the control knob.

Since my 97 has manual controls, are the blend door actuators in the system or is it all cable operated?

I just need some help in how to diagnose the blend door/linkages to ensure they are moving fully in the correct direction for heat.

Thanks!

[19963.4lsr5]

Your heater core can also be plugged.

Remove the lines to it and blow compressed air backwards through it or water from a garden hose.

You can also reverse the heater hose lines if you can find hoses long enough. But the debris will go into the engine instead of on the ground.


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[phattyduck]

Originally Posted by 99SC4Runner

Since my 97 has manual controls, are the blend door actuators in the system or is it all cable operated?

It will be manually controlled (cable) with the heater valve. You should be able to hear it flop open and closed when you move the temp quickly across the range of settings.

-Charlie

[99SC4Runner]

I could hear the blend door make contact in the HVAC box, so I decided it was most likely the heater core was plugged.

I decided to flush the heater core to see how dirty it was. I flushed it in both directions 3 times until it was only clean water coming out of it. Then I took my air blow nozzle and blew the water out, then filled the heater core with coolant.

​​​​​​​Went for a drive and now it's blowing 178° out of the vents with the heater on High. It feels like a normal Toyota heater again now.

[Romeo1]

Super common problem on these due to owners before the second hand guys who don’t pay attention. They don’t clog overnight. It takes a while.

[Sparky 97Runner]

I had a low heat issue with my 97 caused by a broken flapper door linkage on my heater box. If the door linkage breaks with the door closed you will have no heat. There is more than one door so you may be hearing other doors moving. I ended up changing the heater box out. Check out this thread that I started several years ago discussing this.

(Solved)Low Heat Help identifying ventilation control cables on 97

[Jarnigan]

I have/had a 97 with no heat myself despite the blower blowing and being able to feel the distinct click from the heat and a/c controls. It’s pretty easy and quick to try a heater core flush so I went that route, after about 20 minutes of blowing brown gunk out of it…I have heat now. I just done this days ago and so far so good.


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