Chasing Overheating Issue...

Interesting mention on the drill hole in the thermostat. I know there is a jiggly valve on it but may be intriguing to try that on an old thermostat and see what happens. Yes, I am sure it doesn’t have the stop leak in it. I bought the truck used, less than a year old with 1.3 K miles from the dealer. An older gentleman had it before me. It looks like play sand…

 

It's definitely an option I have been looking at. I see there is a larger aluminum radiator and 170* thermostat as well.

 

You are seeing about the temps I had before all this happened. If I could get the temps more under control I would have no problem investing in electric fan conversion. AZ is just brutal on cars though.

 

Lower temperature thermostats aren't really a solution, once the t-stat is fully open if the cooling system can't shed the heat being created the temperature will still rise even though you started from a lower set point.

Also lower temperature t-stats can contribute to sludge build up although maybe not in AZ.

You might consider adding a large transmission cooler before the radiator cooler, this would remove most of the heat load of the transmission from the cooling system.
You do want to keep the radiator cooler in the circuit however.

 

For what it’s worth, ALL automatic transmission 2G Tacos are set up that way - ATF thru bottom of radiator - regardless of whether they have the towing package or not.

I think the OP is just pushing up on the limits of the stock cooling system which seems to be working as designed given the oven-like place he lives lol.

 

I know it's dusty down there in the valley, especially when the Haboobs roll through or if the truck has been down a few dirt roads. I'm not suggesting that some nefarious actors have put sand in your coolant but the dust could make it's way in there none the less since the cap seal isn't perfect. I know it hurts to spend more money on coolant but if I were in your shoes, I'd flush the system out with distilled water a few times like in the video I posted in my previous post. It's been a while since I took my thermostat out but I don't remember if the actual valve can be removed from the assembly. If you still have your old thermostat you could check. Make sure you keep your heater on full blast when flushing to help flush the open heater core. There's a way that you can flush the heater core with a garden hose, but I wouldn't go that extreme since your vehicle is still relatively newish. Keep running distilled water through your system until it comes out clean. You can remove the little rubber plug from the bottom of your overflow to rinse out the sand and when completely finished, make sure you burp all the air out of the system. It may take up to 10 to 15 minutes of it running to get all the air out with you squeezing the tubing. Don't forget to ensure that you have the new thermostat installed.

-J

 

That doesn't seem to be an insignificant amount of sand and shouldn't be there. If that much is landing in the reservoir, I would suspect there is more in the system. So the questions I would have are how did it get there, and how much more is still in the system? I'd certainly be doing some flushes with everything possible open to get it out, and monitor from there.

 

I don't disagree, but, people live in places like AZ and deal with this, and much hotter, on a daily basis. OP has alluded to the fact that this hasn't always happened and many others on here don't seem to experience the same issues in 95° heat.

 

Haboob is how it got there. It'd be a safe bet that the air filter and cabin air filter have the same sand in it. Granted, those are a bit easier to change out.

-J

 

Oven like heat is being nice! I will admit that the heat gets pretty bad here and I don't expect the cooling system to be able to keep the temps down as it would in 70* weather. The temps that I am seeing are about 10* higher than what they were before the problem initially started. If I could get it back to 194* in town and 199/200* on freeway I would be happy.

Sounds like start with flushing with distilled water and get as much of that crap out as possible. Where it came from is beyond me. The truck has 96k miles on it and cooling system was opened once by the dealer to do a cooling system flush(supposably).

You would believe the amount of sand that get in the air filters. You can pretty much build a sand castle with it. Unfortunately, we are starting monsoon season and that when we get the majority of our dust storms.

I will also see if I can get the trans fluid cooled down more before it hits the radiator with an trans cooler. I have been looking at upgrading it maybe its time to pull the trigger on one.

 

Running the heater isn’t necessary because coolant gets pumped thru the heater core all the time anyway, regardless of whether heat is on or not.

Also, cheaper ($13.75/g) source for OEM coolant here below. I used this when I changed my water pump recently. It’s made by Aisin, just like the pump. Toyota just rebrands and charges more:

https://www.rockauto.com/en/catalog...144,cooling+system,coolant+/+antifreeze,11393

 

What if you had a pinhole in your trans cooler?

 

You mean inside the radiator? How would I be able to tell? Have a sledge kind of thing when I take the radiator cap off?

 

No there is a separate cooler behind the grill. (I didn't see if you had a manual or not) but it snakes through the radiator subframe and sits behind the grill, but in front of the condenser.

Tow packages have this.

Edit: that has trans fluid in it, and not coolant. Sorry for the confusion.

 

I know which one you are talking about, I haven't seen any fluid on it or in the area.

 

Oh I know it, I spent most of my formative years living in the valley until the calling sent me on a different path. I remember making dashboard chocolate chip cookies in high school. I'm well aware of the heat and sandstorms. I do miss those monsoon storms though. Sitting up on South Mountain and watching the storms roll in from that parking lot.

Old habits I guess.

-J

 

Check the nipple in the overflow / res tank. Im pretty sure thats where my sediment came from (I hope anyway). I took the garden sprayer to it and flushed the tank out best I could before draining the rad

 

I didn't see that, awesome catch! I will have to check that out and see if that's it.

 

If the temp cycles up and down you have a pin hole leak some where

 

just a normal cycle up and down while performing the same task? Or do you mean as I’m driving? The temperature is high I kind of stoplight it goes down. I start driving again. It goes back up and on and on.