I just recently got an Ultragauge and it was reading an average of 203 while rolling down the highway on a road trip. Is this normal? The truck has 295k on it. I was afraid the head gasket was going to fail 800 miles from home.

That's a little high, but it's not overheating. Most folks see 188-192 degrees. Common reasons for running warmer than that are old/clogged radiator, thermostat with the jiggle valve at 12 instead of 6, or old coolant. An aftermarket bumper that restricts too much air flow can also cause that, but it usually has to cover quite a bit to be an issue. A few people have reported temps in the range you're seeing when the fan clutch is just starting to fail as well.

EDIT: Forgot to include failing radiator cap as well.

You're running too hot for a 5VZFE, but you're not going to hurt anything in the near term with those temps. Needs addressing though.

Inspect items in order from easiest to most intensive:

1- Radiator cap. If not keeping pressure, you can heat up.
1a- Inspect coolant level and condition. Is it low? is it murky? Is your overflow tank empty?
1b- Inspect radiator itself. Is the top of it coppery brown colored? Any cracks anywhere? Have you ever replaced the Rad? If yes to any of these, time for a radiator and coolant flush with Toyota Red coolant.

2- Fan Clutch- Test it. Search Youtube for Timmy Toolman fan clutch test to see how.

3- It could be your Thermostat jiggle valve in the wrong position. You'll have to drain the coolant from the radiator, remove the lower hose, and remove the thermostat housing to see. It's not too hard. the little wiggly valve needs to be at the BOTTOM 6 o'clock position, not 12 o'clock as many techs mistakenly install it wrong.

4- If all of the above checks out, when's the last time the water pump was replaced?


Just a starter list!

In my case, I was running 209-211 on the highway. My jiggle valve was the culprit. After putting it at 6 o'clock, I never go over 194, even in extreme duty.

With my 98 4runner with an aftermarket bumper and winch on the front, I've got restricted air flow through the cooling fins of the radiator and that's one reason why my 98 runs hotter than my 2000. Another reason is all the extra weight my 98 is carrying all the time. Bumpers, full compliment of heavy duty skids and a steel roof rack. The thing is a beast so the engine struggles which causes higher engine temps. So, with the California hot weather we're having right now, I saw high 190's and low 200's driving on a recent trip.

My guess is your thermostat jiggle valve isn't at the 6 o'clock position. But, first check the condition of your radiator cap. They are known to fall apart and the spring and plastic cover end up inside the radiator. The result is they don't keep proper pressure on the cooling system anymore.

I probably wouldn't expect a problem with your fan clutch because you're overheating while driving down the freeway. A dead give-away your fan clutch is the culprit is when you're overheating while in stop and go traffic. When you're at a standstill or driving very slow, the fan clutch is doing the bulk of the work to pull air through the cooling fins of your radiator.

This video might help you out:

At your milage I’d replace the rad if it’s never been replaced. And all three 4Runners had a broken rad cap.


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Make sure the jiggle valve is at 6 as others have stated.
New radiator cap if original.
Newness of the water pump and fan clutch?
Make sure to burp the snot out of the cooling system when replacing coolant. I have had to burp my cooling system for up to 20 minutes on an incline, then shut it off and naturally let the coolant cool down. Now between 186 and 190f in the sweltering South with the heat index at 110f and AC on.

In case its gone offroad where tallish grass is involved, after removing front skidpan, look up between a/c condensor and radiator, clean out any grass or other debris between the two for obvious reasons. Luck.

It helps to include where you live and if you were running the A/C. I know how hot it can get in Chico and I'm guessing you were running the A/C system so that's a totally normal temperature to see. The vehicle will fluctuate from the 180's in the winter months to a max of 210 in the summer (100+ weather with A/C on in stop and go driving) which is all considered normal.

Note that the gauge won't budge an inch between 180 and 210 degrees. Only once you start to push 220 or higher will the gauge creep towards the red. Around 250 degrees you'll hit the redline and experience cooling system failure.

The water pump was replaced less than 2 years ago.
The radiator just before that. I had the coolant flushed and replaced while this was happening during my trip. I did not use Toyota red. I was not running the ac. In fact, I ran the heater which typically brought it down between 194-199. When I came to a stop it began to spike up to 215, but cooled back down right as I got moving. I'm thinking i will look at the thermostat position and maybe try a water wetter. Thanks for all the replies everyone. You all stay safe out there.

It's probably your jiggle valve, given this info. I'd start there. Free and easy fix

That to me sounds like fan clutch starting to fail in combination with radiator cap or thermostat jiggle valve.

I agree.

I think you are on the right track then. 215 with A/C off and heater on is too hot. Imagine if your A/C was on, it'd be 225 easy.

My apologies if this is the wrong place to ask, but I can't figure out the threads... I am in need of changing the coolant temperature sensor on my 4x4 V6 4runner. I (think) i've found it at back center of motor on top, but there is a hose preventing me from getting my socket on it. What is this hose, and can it be moved or removed to gain access to the coolant temperature sensor?
Thanks in advance!

If it's a 2004 then you have a 4th gen. You want to ask that question over in the 4th gen section.