Overheating

I have a 08 prerunner and never had any problems with it until now..I'm constantly driving 4-5 hrs one way and never have problems but the minute I get in to the NC mountains with different elevations it starts to overheat..I kick the heat on full blast and it slowly goes down...so my question is will the different elevations cause this issue or do I have problems with the temp sensor or thermostat... just hit 90,000 miles...

 

I'm guessing you hit sustained hills when you get to the mountains. So it's likely the increased load overcoming the cooling capacity, not something caused by the elevation itself.

since it goes down with the heater on, it likely isn't a sensor. I wouldn't suspect the thermostat if the truck gets up to temperature and operates normally for the rest of your drive.

Have you checked the coolant level?

 

Elevation causing overheating, ?
1 Check for coolant level
2. Check if the radiator cap is sealed correctly and working, but I would say replace radiator cap.

If change in elevation makes your truck overheat, faulty radiator cap is usually the problem, followed by faulty thermostat.
But Thermostat would most likely get stuck from time to time in lower elevations.

 

I would suspect either the Thermostat or the cap.

 

You're pushing 100K, Toyota's 1st planned coolant change. You may have done that already. If not, do it along with what's been suggested already.

New T-Stat and Radiator Cap. Be sure to bleed the cooling system. Countless discussions on how to do this.

Might not hurt to also ensure front of radiator & a/c condenser are not full of stuff...bugs/etc radiator

 

Always keep my maintenance up and never a change with the temperature until I moved to the mountains..coolant level is where it needs to be...I'll check the cap in the morning when I get to work...I work for carquest so getting parts isn't a problem

 

The other thing to check is the hose itself. I've seen older ones basically collapse under pressure. The nicer replacement hoses have (for the lack of a better word) what looks like a big spring in them that will not allow the collapse to happen.

If you decide to switch out the t-stat the other thing you might consider is a complete radiator flush ... not just the drain the radiator and refill kind .. the complete back flush kind..

.02

 

I have not seen OEM Toyota hoses that have the internal spring support. Do Toyota OEM hoses for the 2nd Gen 4.0L have this?

Thanks.

 

If it has a clutch fan check it. They are temperature activated and when they fail they usually will not engage themselves and pull the necessary air through the radiator. Just an idea.