It was a little cool today, so I turned on the heater. Initially, the A/C button was on when I turned the heater on, so I turned it off. Now, the temp gauge is reading hot, in the red zone, with the heater on. What is causing this? Is the heater control, somehow, causing the engine temp. to spike? While driving, the temp gauge did not fall much below the red zone. I turned the heater off, and the temp. gauge seemed to drop. What is causing this latest problem with our 99 4Runner?

 

this is info on the 22re, which you wouldn't have in your '99, but it may be the same idea and worth checking out.

http://4crawler.com/4x4/CheapTricks/...tml#Thermostat

mike

 

Thanks for the info, I will look into it and see what I can find out.

 

This makes sense, this is why a toyota engine warms up quicker - giving quicker heat then all others

Matt

 

I checked the engine over during my lunch time and found the antifreeze to be low. I added about 1.5 gal. of mix. The engine does not get hot now. The heater still did not work, I was able to pull the hose, that goes to the control valve, off while the engine was running, no anti-freeze came out. I poured water into the hose with the rad. cap off (engine off) to "flush" out the air, then, I replaced the cap and filled the hose with water. I put it back on, then started and revved the motor. The heater works as it should and the engine does not get hot now. So, looks like I was low on antifreeze and then developed an air lock in the heater sytem.

 

ahh, a far simpler solution i guess that goes to show that we should always think of the simple things first.

 

Indeed, and check them a wee bit more often...

 

Filling the rad is not a solution. Leaking fluids are symptoms, especialy in a closed system. You should keep a very close eye on your coolant level (daily) and for drips under the truck.