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 there 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!

 

This might help. I'm not sure if this only applies to vehicles with A/C or not.
The info is limited. I'm guessing it might have something to do with the Air Mixture Cable or whatever it controls.

 

I had that trouble with my 99 4Runner this past fall. IE No hot air out of the system. I verified the heater control valve cable was installed and aligned properly, as my mechanic replaced the valve recently. I was worried that this was going to be a COLD winter.
I then leaned over the passenger compartment side of the cab, and looked to see what I could see. The air control cable's outer sheath wasn't locked down in it's clamp, so when the dial was turned from hot to cold or cold to hot, the outer sheath would move back and forth, but not the inner cable. The one actually connected to the mechanism as shown in step 2f. I matched the position of the knob to the position of the mechanism, in this case full cold, and locked the outer sheath into it's clamp, again, as shown in step 2f. I then ran the knob to full hot, and lo and behold, I got HOT air coming out of the system. It was so hot, I had to turn the knob down to about 1/2 way through the white area. The middle rectangle on the knob's markings, or it would bake me out, even in the middle of a snowstorm I had to drive through one night.

Don't know if this is any help or not...
Pat☺

 

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.

 

Well, I'd say you solved it! Congratulations

Enjoy the warm (hot?) air

Pat☺

 

How much crud came out of the core before you got clean water?

 

I had the same issue in my old Subaru, it made me absolutely cringe when I walk by the alumaseal / fix your radiator leak with this tube of crap isle in any local parts store………stuff should be illegal.

 

I flushed the heater core in both directions 4 or 5 times before clean water started coming out. It didn't look like mud puddle water, but it was dirty. Then I took my air hose and blew the water out of the heater core and filled it with coolant.

With it being 4* this morning though, my heater is warm but not roast me out of the cab hot. I'm thinking I'm going to have to get a brand new heater core and install it to fix it correctly.

 

While you had the core out, did you blow out the fins? I'm not sure about the third gen heater cores, but I KNOW for certain that the first gen heater cores collect hair, leaves, and DUST in huge quantities. After long enough, compressed air isn't enough to clean them any more. You need soapy water to get the cryd out of the fins. The dust etc forms something like a concrete brick around the fins, blocking air flow though them, and reducing the effectiveness of the heat exchange of any air that can get through.

Just a thought. I get so few of them any more...
Pat☺

 

I didn't remove the heater core or remove the HVAC box yet. I just unhooked the hose from the water valve on the firewall and the other hose from its source, and then I flushed the heater core that way. I will remove the blower motor and try to see in the HVAC box to see how it looks. If I have to remove the HVAC box, I will just install a brand new heater core while I have it out to clean it.

 

Sounds like a plan

I wish you all the best of luck. Watch the rear heater core water feeder lines. They're metal after a certain point in their routing.They're prone to rusting out. A lot of people just cut them off short, and put a small piece of heater hose across them when that happens. If you want the rear heater to work correctly, if you have one, keep a sharp eye on them

Pat☺