Avoid Overheating Turn Off AC Next XX Miles

I live in AZ and there is a sign similar to this on I-17 North from Phoenix going up the grade around Black Canyon City. Summer temps here can easily hover around 110 plus. The grade is not that bad and the speed limit is 65+ on most of the stretch. With modern vehicles and properly working cooling systems is this even a thing or necessary? I have traveled this route many times in 7-8 different vehicles with my AC going and the temp gauges only went a bit above 1/2 but not even close to overheating.

 

I have never turned my AC off or had a problem. I tow my travel trailer up those hills at 65-70 with the AC on full blast in July on my way up to Williams or in your area at Dead Horse Ranch.

 

If we have to turn our air conditioning off for hot weather and 8% grades, then we purchased the wrong trucks.

 

It is. Next time you go up I-17 look for the burn marks on the road from vehicles catching fire. Usually transmission overheats and vents tranny fluid, everything else is hot and poof fire. We have Toyota Tundras though, AC on, hammer down, left lane.

 

From what a trusted old-timer mechanic friend of mine told me, that comes from an earlier era where derated and underpowered engines required high RPMs to climb the grade and the A/C clutches were cycling causing premature failure combined with engine cooling issues and the need to reduce the load on the engines to keep them from overheating. Manufacturers have learned a thing or two about cooling systems since then. We now pressurize the cooling systems to rather high pressures thereby increasing the boiling point of the coolant by roughly 3°F for every PSI increment at sea level.

I live and travel in AZ during the summer and never turn off my A/C climbing any grade regardless of the vehicle we take even when towing my trailer fully loaded.

 

I used to live there... gosh I miss it. But I think those signs are mainly for our little friends missing most of their cylinders

 

I’ve never had to turn mine off in all my years of traveling the basins.

 

What about in the valleys?

 

Yes, my dad was a truck driver in the later 50's and I remember him talking about vehicles limitations back in those decades. He also used to mention about having to change the timing when in higher elevations.

 

The true valleys have no issues either.

 

This is one of the things that makes me wonder if I should install a trans cooler on my '19 since I occasionally pull a trailer.

 

My parents used to live in Prescott Valley and I passed that sign a lot, always chuckled, left the AC on full and drove past it.

 

I’ll take it out of OD but that’s about it, and not even for that reason.

 

It's not going to hurt you to install one. If you have the time and money for it, pop it in and then you don't have to wonder. Just don't pin the thermostat. There's a silly myth that this makes it cool better, but it doesn't. It just makes it take longer to heat up the fluid to operating temps where it works best.

 

Luckily this must largely be an issue of the past. The tundra cooling system seems quite adequate I will say (both engine and transmission) I’ve noticed no higher coolant temps or transmission fluid temps towing heavy in the dead of summer even pushing the truck on hills with the added heat of pushing around 600 horsepurrs and torque on the stock cooling system. Might upgrade to the CSF radiator one day if mine springs a leak.

 

Lol. Do you live here and have any experience with pinning thermostat open? It’s a thing here to pin it in hot temps, and I have a few Toyota friends, they do a tiny bit of testing in the basin or valley or whatever the hell I live in.

 

I take it I'm the only one to turn ac off during desperate times?

 

In hot temps the detriment of it staying too cool longer is reduced, but there's not a real benefit to pinning it. At least I've not seen any data to support it. If you have the data I am completely open minded on the topic, but if it actually worked better to pin it, why would it be engineered with the thermostat in the first place? Why wouldn't they recommend pinning it in hot climates? It's unnecessary.

Say it's super hot so you want the thermostat open all the time, well it opens based on temp and if it's hot enough it will be open all the time. Pinning just makes it take a little longer to get up to the (random number here) 200* that it's going to be cooled to and run at anyway.

 

Like people who put their AC setpoint at 60 thinking it’s going to give them colder air, when in reality it’s nothing but an on/off switch at said temperature.

 

Well, this is a rhetorical statement, but...
If ac doesn't cycle on and off, it gets the vents cooler and cooler vents mean less cool air is needed to cool the vents, hence cooler air coming out of the vents.

It should technically give you cooler air, but not for the reasons you might think. Simple folk are genius!

 

DIVERT not convert is what the Cap'n says....

 

Do you honestly expect me to take advice from somebody that doesn't even know if they live in a valley or a basin?

 

Yes, you are.

 

Rivers and boundaries need to be drawn……

 

I think that was for older cars; I met a guy at a car show who said he had to crank his heat driving through Death Valley in the 1960s. I believe he was either in a Ford or a Plymouth, but I don't remember...

 

There's always that guy driving the 94 geo metro that is struggling to make it up the hill going 37 mph and not letting anyone pass. That signs for him.

 

You are correct about the era. The early 1960s cars had a vented radiator cap and therefore atmospheric pressure. That means boil point is 212°F at sea level and somewhere around 210°F at 1200 feet. Those cars boiled over really easy. We've come a long way since then. Our engines last longer now too along with the longer oil change intervals.

 

So I’ve had to much fun zipping up that hill in my sisters civic, maybe to close to, to much fun. But the most fun might have been in the duramax; I deleted lots of the logged max and top speed points on my dads controller thingy after that, the old Italian tune up (@Darkness)

 

My Tacoma boiled over once but didn't actually overheat. My truck is a 2010 with the 2.7L 2TR-FE, and more than 155K miles, and it has had no major engine work done. I found the coolant in the expansion tank to be low and filled it. This was a mistake because my coolant level fluctuates greatly with outside temperature, and there was actually plenty of coolant in the system. It literally blew the expansion tank cap open and splattered coolant all over the engine bay. I say again that my truck has never overheated., and I ended up using a medicine dropper to decrease the coolant level.