I was heading up the mountain in my 1997 V6 2WD 4Runner with the AC full blast in 100+ weather in NV, I was riding it pretty hard due to traffic behind me and all of a sudden boom pink coolant all over the window and pulled right over. I bought this 4Runner a few months ago and have done a lot of trips already with no issue. When this happened the temp gauge never went above half way before the overflow cap blew off.

I have been researching all night and my plan of attack was the thermostat, flush and burp. However after registering on Toyota to see maintenance records, one year ago exactly previous owner reported an overheat. Toyota replaced the front heater core under the dash due to leakstop clogging it up, all clamps and lines, flushed the motor, replaced the radiator, thermostat, and bled the cooling system. This leaves me stumped on where to start, the radiator cap looks old even though the radiator looks new so I was going to at least replace the cap, and debating checking the thermostat for the 6' oclock position even though it was installed by the dealership, and cleaning the AC condenser since it looks absolutely horrible.

Any other ideas? The timing belt sticker shows 140,000 and I am at 194,000 but no service history on the site shows the belt and water pump change. Could the outside temp, AC full blast and pushing it just pushed it too far? I have a huge camping trip planned end of the week so dont want to be stranded.

 

I had a near overheating scenario last year in my ‘99. It was super hot out, had the a/c on max, and was in traffic. Cooling system started to creep up, I noticed the gauge, switch from a/c to heat backed off the throttle and got to side roads so I could keep air flowing thru the rad. No other issues to report in 15k miles.

it could be that the a/c, the load of pulling a mountain side, and the ambient heat were too much to shed. When you are running the a/c, you are introducing a heat source (the a/c coil) in front of the radiator. So the radiator isn’t getting drag coil air, it’s getting hot air.

another thing to check, is your truck an auto? If so, it’s possible it milkshaked. Although if the rad was replaced last year I doubt it would fail so quickly. Just something else to investigate.

 

Thank you for the input, I will go ahead and flush the water I had to put in and add the red coolant as well as drain and fill the transmission to take a look. I need to do the transmission at this point anyway, not sure if it has ever been done.

 

 

What is this!? I also took the top line off and you can see some sort of thin brown flaky material lining the inside of the part of the motor where the hose connects...

 

New rad, heater core and fluids doing that in a a year, strange, definitely need a couple flushes. maybe the PO was running it on Tap water or pond water?, I don't think mixing green Ethylene Glycol with Toyota Red would do that, toyota didn't use the Red Ethylene Glycol till 1999.
I noticed yesterday at 95*F outside temp, AC on, while climbing big hills, on my scangauge my temp was up to 215* but the dash temp gauge was below half still, I normally run 193*F rock steady, but yesterday my trans and rad temp hit 200-215 a couple times.

 

Definitely odd, it does look like tap water or that they overheated and threw pond water in lol. Will report back after flushing and swapping radiator.

 

Bear in mind, it might take more than one flush to get all that rust out. Maybe one with a flush chemical of some kind, and then a few with just clean water. Then replace the radiator with a nice CSF 3 core all metal one.
Maybe the thermostat, too. I hate to think how much crud had collected on it. Same with the hoses. How much of that crud has collected in them? That stuff is pervasive (my big word of the day!). You MIGHT even want to do the water pump. Or at least take it off and rinse it out with the garder hose and a spray nozzle, you know?

Good luck, and keep us in the loop on how things go for you
Pat☺