No heat - Toyota 4Runner Forum

imdav2u2 · 11-03-2019, 04:05 PM

I have a 1998 4Runner that I purchased new. It has been sitting for the past 2 years. I got it out , cleaned it up and it has been running great. I turned the heater on and it is barely warm. The heater under the seat gets hot. I replaced the valve on the firewall, both hoses going in and out of the heater core get very hot, I backwashed the core but still no heat. Any ideas?

heat · 11-03-2019, 04:19 PM

sounds like air control doors under the dash aren't opening or
closing fully.

imdav2u2 · 11-03-2019, 05:01 PM

Thanks to post by nissanh, I found where the control arm that opens one of the doors was broken off. I drilled and put a screw in it so it works properly. My heat is better but the heater under the seat still puts out more heat.

Drew76 · 11-04-2019, 08:15 PM

Quote:

Originally Posted by imdav2u2

Thanks to post by nissanh, I found where the control arm that opens one of the doors was broken off. I drilled and put a screw in it so it works properly. My heat is better but the heater under the seat still puts out more heat.

I see you replaced the valve at the firewall, My servo motor would run but was too weak to move the valve properly, try disconnecting the cable and moving the valve manually. Now, twice a year I just move it one way for heating season and move it back for cooling season. next guess would be heater core but you back flushed it and both hoses get hot so not sure.

nissanh · 11-05-2019, 01:03 PM

May be you have some residue inside the heater core. I used 10% vinegar and allowed it to stay inside the core for 1-2 days and flushed it out. I repeated that process over a week to clear the heater core in my 2000 Landcruiser and it is now blowing hot air.

The calciumcarbonate in most city water (if you live in desert area, the concentration of it is high) can built up inside the core clogging the channels. Adding vinegar dissolves it but slowly to form water and carbon dioxide.

brillo_76 · 11-09-2019, 07:58 PM

This is why for years. I only mix antifreeze with distilled water. As you dont want the minerals or chemicals from tap water in your cooling system. So much of the city waters or even spring water are heavy mixed with minerals and these minerals like to build up in your radiators and heater cores. :[

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