Just bought an 85 4Runner last night and everything was perfect when we were test driving and all fluids were golden. The drive was from Seattle back to Idaho from about 10:30pm and finally got home at 5:30am. About a half hour into the trip I don't know if something could've froze up since it was maybe 2 degrees out at snoqualmie pass but the temp gauge didn't read anymore and heater wasn't blowing hot. Maybe a tiny bit warm but not hot. Stopped and checked radiator and it was full. The radiator itself was hot but cap wasn't and took it off without any bubbling out. Upper rad hose was pretty hot but bottom was hardly warm. Couldn't stop cause there wasn't any 24 hour stores and would've froze to death sitting somewhere so I drove it all the way home but motor ran perfect and made no funny noises. Not sure what steps I should take to fix this issue. Burp the radiator maybe?

 

Maybe thermostat stuck open. There should be at least some small pressure in the radiator at correct operating temps.

An engine that is in good condition and properly timed, does'nt reject all that much heat to its cooling system.

Sometimes it's necessary to shutter the radiator with some cardboard in order to get decent heat when under low loading, or at high speed cruise when its cold.

Look at how shuttered the 18 wheelers run in cold conditions.

 

Thanks for the quick response. Now that I'm in town should I go test it out and see if it's better than the below freezing highway temps.

 

Can't hurt, you're gonna have to get to the bottom of it sooner or later.

 

It should blow hot even coming out of the vent. One thing about the first gen runner is when it does get extremely cold, if you have one with out the rear heater and in real cold weather you can freeze inside the truck. I have two runners, one with the rear heater and one with out the rear heater. When it is bitter cold, I dont drive the run without the rear heater. I use Peel and Seal on the rear panels and it does help keep heat inside. There are other materials you can use to insulate the rear panels. There is just to much space for one heater to warm up in my opinion.

If yours did not come with AC, it is possible that the heater core has gotten dirty. https://www.yotatech.com/forums/f199...l#post52002149 If you have AC, the Evaporator will catch the dirt.

https://www.yotatech.com/forums/f116...trucks-286766/ Make sure your valve on the firewall is open all the way and allowing fluid into the heater core.

As far as your temp gauge, the sensor may just need a good cleaning, located in between cylinders #2 and #3. It can get a crust build up on it and a brass tooth brush will get it operating. Other wise you may need to have your radiator cleaned. The Preston Flush kit will not get the 20 years of build up out of the radiator. Take it to a radiator shop and have them power flush it., It will look like mud coming out of it when they flush it. Nasty stuff in there. Sounds like you just need to go thru the cooling system and ventilation system real well.

 

Thanks for the responses. Took out the old thermostat and it looked pretty darn rusted. Threw in a new one and also let it run with the rad cap off to see if it would burp out air bubbles. Temp gauge now sits right in the middle and I get some good heat my way

 

Thanks for telling what fixed it!!

 

Seattle has a seemingly endless supply of 85 runners. That's where I found mine. Post some pics up. How much did you pay if you don't mind me asking.

 

 

Nice find. Looks like a solid rig.