What are these ScanGauge temperatures telling me?

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Sep 23, 2009
Hurst, Texas
I would really appreciate some insight and input from those of the Forum who know about such stuff... what are these ScanGauge temperatures telling me?


  • 1996 FJZ80
  • stock tires & gears
  • original radiator
  • recently-installed TRD supercharger
  • Snorkle.

Ambient temperature: ~88 degrees (F)

A couple of hours "running errands" and I noted the following:

On "primary artery" streets, averaging 40 MPH or so: Water temp (WT) = 196~198, Intake air temperature (IAT) = 109~112

A bit of "freeway" driving (this was the surprising part): at or near 60MPH posted speed: WT = 198~200 (but would occasionally drop to 195 (!) as freeway speeds slowed). IAT = 109~115

On back sreeets (the "stop and go" 30 MPH streets): WT = 195~197, IAT = 110~122

There seemed to be a "sweet spot" for water temperature around the 45MPH mark... occasionally dropping to 195

After sitting for a few minutes, the WT would be 202 to 207, but would drop back to 198 within only a couple of blocks of driving.

I'm wanting to be sure that I understand all this before we hit the road towing our CASITA camper!


Looks to be 2-3 degrees higher than my normal temps (especially heat soak when stopped), but that's probably to be expected with a supercharger. I don't have one. I would probably say your fine but the supercharged guys should chime in.
Thats a bit to warm. Mine is almost a constant 190 with ambient temp of 93.

Replace clutch fluid with 10k. It dropped my temp about 6 degrees.
They seem to fit "normal" for a non super charged truck. I think you're well within the range of normal for a super charged truck.
I just got a sc too, so it's too early to comment on my temps. But, my before temps were 184-190 town/freeway. Intake air temp varied, but I have a snorkel so that may make a difference too. I replaced the original radiator with the older style one along with a new water pump and blue fan clutch last summer. I also did all the heater hoses and phh too. I would think your temps are just a bit high, but I am not sure how much difference the SC makes. Give me a few weeks and I should have some better temp data soon. Being that summer is approaching, I'm hoping everything on my cooling system is fuctioning properly. Have you replaced the water pump, thermostat, or fan clutch? What about coolant? What is the history on that? Most of it is just general maintenance and after seeing how you did your hood vents, should be a piece of cake for you :)

190°-210°F is normal
You want your motor to run in that 200°F zone for max efficiency.

too cold, it will increase wear and not run efficiently
too hot, it will cut A/C (around 225°F ?) and good warning to back off

New cars are good at getting to 200°F asap and staying in that zone for max efficiency.
Your truck is running normal temps. Keep an eye on it when towing.
Thats a bit to warm. Mine is almost a constant 190 with ambient temp of 93.

Replace clutch fluid with 10k. It dropped my temp about 6 degrees.

Funny you should mention that... picking up the 10,000 CST silicone was one of my many stops today!

I have the upper and lower radiator hoses on the way from Dan, along with the 'Dan-fan.' When all that stuff gets here, I'll spend a day or two installing those and changing the clutch fluid.


Have you replaced the water pump, thermostat, or fan clutch? What about coolant?



When the S/C was installed, the mechanic said that the water pump was perfect (even though it is the original, 137,000 miles). The t'stat seems OK, too. I will change the clutch fluid to the super-gooey 10,000 stuff in a few days, along with a system flush and refill. PHH replaced with the good stuff a few weeks ago.

I'm getting there (I hope, I hope, I hope)
Mine is usually mid to upper 190s in most conditions, once warmed up. No S/C for me :^(
I see these with a modified temp gauge, so I'm kinda guessing the temps with what has been posted before. I'm also supercharged, with 10k cst in the fan. No cool vents though :flipoff2:

Normal Stop and Go : Halfway to slightly above half (185-195)

Highway driving 80mph: Halfway (185-190)

Going downhill on highway: 1/4 to 1/2 (160??? - 185)

Going up steep grade (about 7% or so) at 70mph: above half to 3/4 (200-215?)

These are all guesses, but it looks like your temps are within normal range.
Not a Supa-charged guy

but, what I like seeing is that your IAT is pretty consistent. I've been pretty surprised to see that the IAT runs, best case (freeway hustling) ~18* above ambient, and then rockets up ~40-50** above ambient in slow-go driving...and more upon heat-soak.

Seems like you're doing all the right things. FYI...my WT runs around 193-195* in slow going, 188* at consistent speed.

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