Running Hot Only On The Highway

You are getting lack of coolant flow at high speeds so my impression is a partially clogged radiator. Hopefully a chemical flush, Tstat, and cap works but if not, you need a new radiator. Make sure to burp the system after the flush.

 

Hmm... at highway speed your engine is doing less work unless you're going up an incline and temps should be steady or even cooler with all that air hitting your rad. I would have suggested rad cap and t-stat and flush while you're at it. Don't forget to drain the block, you'll get another gallon out using the block drain on each side. When's the last time you flushed your coolant on your 2012?

 

@ecliff5

 

Im between 190-200 yr round, it rarely gets/stays in the 90s up here

 

Easy test also, if you have not yet installed some parts.
Remove the grill and go driving the same path. See if the temps lower.

 

It has 101K miles and I’ve never flushed it. I’ve had it for ~30K miles. I’ll be doing it as soon as the parts arrive.

 

Currently dealing with the exact same thing on my 06. 150k miles. Started seeing the temps rise to 198-204 on highway and up hills the past few months. Popped my rad cap and it looks the same as yours, orange/brownish. Had Toyota do a super flush and it didn’t do anything. I actually don’t even think they did the flush so I called them out and am having it flushed again this Saturday and will be watching them do it this time. Also have my 80 series in the shop and working on the cooling system. Pretty bummed that my taco is now running warm, really don’t want to do the cooling system on 2 trucks at the same time. Will be following up on this thread.

 

160° T-stat. Upgrade the radiator. Done.




Well....unless your '06's head gaskets are on their last legs..... Fingers crossed that they aren't.

 

No signs of head gasket failing. I’ve been very cautious of this having an 80 series with over 300k on it.

If the coolant flush from the dealer doesn’t help this Saturday I’ll start looking into alternatives.

 

I had an 80 too. Was always fighting higher temps on it mostly due to high IAT (140+ degrees). Snorkels really help cool them by breathing that much cooler air.
Redid the whole cooling system on it, with new everything, and it really helped.

 

I have a 2014 with a Pelfrey front bumper and have the exact same problem. I have found that per a Toyota Service manual the OEM t-stat isn't fully open until 206. On mine, when going above 65 mph, it will climb to 198-206-7 depending upon the load. I have only see it go above 207 one time. The air temp was 117 and I was going 70. It got to ~215 before I let off and went 55 to cool the truck. This was a couple years ago.

To save you parts...My radiator was clean. I bought one of those High Performance CSF radiators for the FJ that everyone swore by. I also bought the OEM shroud ~550-600 total for everything I bought. Replaced the hoses, coolant, t-stat and radiator. Only thing not replaced is the water pump. Guess what??? If anything, the damn thing gets to the 206 faster than before when under a load (ie. climbing the hills out of Phx). On flat ground it is a little cooler 200-204. Though around town, sub 65, it is cooler. I live in the Phoenix area.

Disclaimer: this only happens when the air temp is ~95+. Never when its cooler than that.

 

Based on my experience with Toyota’s service flush, they fail to burp the system. I don’t have a scan gauge/ultra gauge, but I started to notice that the temp gauge in the truck was sitting a little higher than normal. I then noticed that the reservoir had no coolant even though it was refilled post-service (checked before leaving the dealership). I ended up refilling the reservoir and rad, jacked the truck up, and burped the system with no more issues to date.

 

What thermostat did you install?

Did you bleed the air from the system with the heater on high?

Your endeavor seems in stark contrast to everyone else's. Unless they installed a 170° thermostat. They had little to no change until they also used the 160° in conjunction.

 

forgive me if it has been addressed. could be your water pump. i have seen impellers corrode the fins off, the impeller come loose and numerous other issues. it seems fine while at idle but and speed its sub par. if your going to dig into the thermostat and put an aftermarket one in, water pumps are cheap enough on rock auto.

 

@MolonLabeTaco . Hows the fan clutch .At higher temps should start locking up so fan flows more air .

 

It is a over the Toyota counter OEM one. Did not change the temp range.

Yes, I idled the truck with the heater on hot and blowing until it reached its normal 186. I ended up having to add roughly quarter to half a cup more coolant the next couple times I checked it, after some drive time. Now it is right at the cap.

 

Fan has good roar at start up and when warmed all the way up. That’s actually the other thread I started, was to see if Taco’s do well with a fan clutch fluid viscocity and amount increase like 80’s do. Then I was reminded, the fan is really only doing its job at slower speeds. Once you get to ~45+mph, the fan isn’t really a part of the equation anymore. Then it becomes a air flow to the front of the radiator or an internal radiator flow situation.

 

Had a feeling. That 180° is a contributor to your continually high temps, in your hot climate Being in your geographic location, you're truck is a great contender for the 160°. The Motorad T-stat part number is in the CSF Radiator thread.

 

That’s not true. Think about it, engine load (or call it torque demand) can be pretty high at high speeds due to the really really bad aerodynamics of these trucks. There’s more that goes into the equation but it’s basically the resistance the outside world puts on the motor, so that obviously increases the faster you drive.

 

Depends a lot on load and RPM as well as air speed/flow across the radiator.