So over the last 2 years my 4runner hasn't been getting as much love/use as it used to, but I still drive it about twice a week. A little over 2 years ago I did the TB, Water pump, valve cover gaskets and belts, all with OEM parts. I used to run a scangauge on it all the time and the coolant was pretty much ALWAYS 192-196, it barely moved at all once it got up to temp, but i stopped running it before I did all of this maintenance. So last summer I used an OBD 2 scanner and app and found out that on my trip up to North Carolina, my temps on the highway were running maybe 215-230 towing a trailer. Pretty concerning. After that I wasn't driving much more than a couple mile trips around town. A couple months ago I added a Scangauge again to keep a constant eye on the temps.

This past weekend I dug into things on the runner to fix my squeaky AC belt, but in a new battery and a CS144 alternator. I went ahead and replaced the thermostat (even though this one wasn't very old) and made sure the jiggle valve was at 6 O'clock (I was thinking maybe I had it installed upside down, turns out it was installed correctly at 6 o'clock). In doing this I also replaced a lot of coolant, which was nice and red. I burped out a bit of air as well, but once the initial air burped from filling up the coolant, no more bubbles in the filler tube. Turns out my Radiator cap was broken, so I replaced with with one from Advanced Auto. At this point I figured that was the culprit.

Things are better, but still running hotter than what I think should be normal. At no point does the needle on the gauge on the dash seem to move about half way, but that thing seems pretty worthless. Temps will get up to about 219 but once I'm at highway speeds they slowly start to drop back down to about 205. I'm thinking the fan clutch might be a culprit at low speeds but driving 70 down the interstate it should be cooling back down to the 190s. Am I crazy?

***Edit*** I am remembering that last spring I would have the coolant boil in the reservoir on my way home (up a small mountain) but I think that was because of the bad radiator cap causing loss of pressure and thus a lower boiling point for the coolant.

How old are the thermostat and the radiator?? I had one go bad at 230K and was sticking shut. IF you turn the heater on both heaters to wide open does the engine immediately start cooling back down? [Most 4 Runners have a back seat heater but not all] If lots of miles and many years on the radiator. I would change the radiator especially if its a automatic so you get the milkshake disaster. Very good thought on the fan clutch as well. You not crazy something is wrong Denso Rads are around $100 on Rock Auto. My temps gauges never move once they reach normal operating temperatures.


When I start my up and the engines cold, you can hear the clutch fan activate for while then freewheel. Of just lift the hood and watch it.

A test is the following:

To confirm the diagnosis, start with this simple test: Spin the fan as hard as you can on an engine that has not been started that day. If the fan rotates more than five times, you can bet the clutch is bad. You should feel some resistance and the fan may spin up to three times, depending on the ambient temperature

I changed the radiator to a new denso when I did the timing belt, water pump, etc 2 years ago, so it's still pretty new. Tranny has an aux cooler in series with the tranny cooler built into the radiator. The Thermostat was 2 years old, but I put a new OEM one in this weekend when I was troubleshooting.

That eliminates the rad and the thermostat. :-] I only use my dash temperature gauge.

I know when you are towing, its going to run hotter. Being working the engine and working the Tranny putting extra heat into your system.

I am sure the FSM has a test to verify your gauge is working properly. I don't how people think they the factory gauges are worthless. I know it showed me when my thermostat was stuck. Saved me from cooking it, that's what its job is to do.

You could always put a cooler thermostat in and see what that does for you

and if the water pump was oem or oem mfg I don't see that causing the issue of temperature.

The replacement cap would have corrected your pressure problem.

So what signs are you actually getting that the engine is overheating?? You stated the temperature gauge isn't up and staying the same as it always has.

Or are you using an Scanner and it is showing you actual engine temperature and thinking it should be cooler.

I know mine even smelled hot and heat off engine was much higher when my gauge was up on the upper white line...


Operating temperature limit for a 3.4?

What is the normal Scan Gauge Engine Temperature?

What is the normal Scan Gauge Engine Temperature?


I will plug my scan tool in my 98 tetanus 1 and see what it tells me the temperature is.. Now you have me curious

I know my gauge on all 5 of mine is always slightly below half with the factory 180 degree thermostat in them. :-)

You do have the bases covered, so I can understand why you are scratching your head. Sorry I couldn't be more help. :-[

replace fan clutch-15 minute job-$80-worked for me...

replace fan clutch-15 minute job-$80-worked for me...

I'm getting temps with my scangauge II. I could be wrong, but I was pretty sure the factory thermostat was a 190. Aside from the coolant boiling last year (hasn't this year, replaced the broken rad cap and not much high stress driving) and just higher than normal temps on an engine that never fluctuated much, there aren't any signs of overheating. I just want to get as many miles out of my 270k engine as possible.

I'll post some pics later tonight, but I'm pretty sure I figured out the culprit. I was looking things over and noticed my ac condenser had a lot of junk in it. About 2 years ago on a wheeling trip i went nose down in a mud pit, enough that water and mud got about 2 inches deep in my passenger side floorboard (and rising before I got tugged out). I'm sure just about the entire radiator was under. 15 mins with a garden hose and i had a nice little mud pit underneath my car. Cranked up the truck and within 2 mins it went from 216 to 190. I'll need to take her for a little longer drive, but I'm pretty sure this was my problem. Pretty pissed at myself for not noticing any sooner.

So as you can see from these first 2 pics, there was enough stuff caked in the condenser coils that there was a ton of junk on the surface, I'm sure there was way more in between the fins. I'm not sure if the radiator itself was as junked up (the little bits I could see were pretty clean), but with the ac condenser coils being that junked up, I can't imagine there was a ton of air flowing through to the radiator. There was a bunch of leaves and junk collected at the bottom which might have been why my tranny was running a little warm too.

You can see the last pic was the pile of dirt/mud that was on the driveway after rinsing it off, which doesn't include the chunk of leaves I pulled out.

I understand wanting to keep the temps down and making them last longer. Mud filled rad condenser and aux cooler will definitely raise your tempurature. I just checked my spare oem thermostat 82 degrees C 179.6 F. So Don't be too hard on yourself. We all boo boo and learn to keep the radiator area cleaner.. :-)
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