Coolant frustration: new thermostat installed wrong way?

seabun

Member
Try to keep exposition short as I can

Driving to San Antonio from OK, engine overheating. Once in SA, Alamo Toyota tells me:
1. radiator is leaking (cheapy aftermarket put in 2-3 yrs ago in a pinch)
2. intake manifold gasket is leaking (gasket to thermostat?)

2 days, $$ later, I get:
1) new radiator (16410-AZ011, OEM but says Denso?)
2) water inlet gasket (16325-62010)
3) thermostat (90916-03075)
4) 1 gal of toyota red coolant (assuming they mixed it w/ water so actually
put in 2 gal)

Back on road, turn on Torque app and while driving at night, no A/C, temp is hovering around 205°, and idlng in driveway it reaches 208°.

That seems too high. When it was overheating on drive down, it was getting into 225°+. Research on here says most of you see temps around 190°, maybe closer to 200° on hot days with the A/C blasting.

I've also read a bunch about Thermostat jiggle valve placement. Consensus says to clock it at 6, or downward. My copy of the FSM confirms this. I check with Alamo and they tell me the new thermostat was installed at 12 and is supposed to be at 12. WTH!?

Please somebody help me out. Our Thermostats are supposed to be set at 6, right? Do diff years have different specs? (Mine is a 1999). Should I take it back in and make sure they flip the Thermostat around before I head back to Oklahoma, which I was planning on doing tomorrow, or say F-it and just do it myself when I get back home?

On an otherwise pain-free ownership, coolant issues on this 4R have been my achilles heel. It makes one of the best things about owning one, roadtrips and excursions, an anxiety-ridden struggle bc I fear anytime I hit the highway I will, like this trip, get stuck midway. Maybe the last thermostat I had, which was also installed at Alamo a yr ago btw, was also clocked at 12??

In conclusion, Radiator+thermostat+gasket are brand new, water pump+timing belt are 1yr old...truck should be ready to ride for many miles (just hit 190k)...but not if it overheats. Will flipping the thermostat ease my worried mind??

Thanks for any and all thoughts!!:usa2:
 

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T-stat installed in the 6 o'clock position is the general consensus around here. My OEM t-stat was installed at the 12 o'clock position, and my truck did just fine for 17 years before I swapped it this winter and put it in the 6 position per feedback here. My coolant temps dropped initially a few degrees but now hover in the General area of when my T-stat was at he 12 position. Splitting hairs with 1-2 degree differences here.

Folks here swear by the 6 o'clock position and some have provided tangible proof this results in lower cooling temps, but in my experience the notable difference in temps pre/post jiggle valve relocation is negligible. I'm almost willing to bet that my paper copy of the fam for my 2000 days jiggle valve at the 12 o'clock position.

I'm guessing your jiggle valve position isn't the culprit here. I'm guessing there's still air in your coolant system and it could use a good burping.
 
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Many members are obsessed with this jiggle valve, 205-208 is not bad, especially in the summer with A/C running. I personally don't remember which way I placed my jiggle valve and have absolutely no problems. As longs as your gauge doesn't hang around in the upper section it's fine, my gauge is always a bit below half, heat, cold, a/c on or off. Besides it's not the thermostats job to cool the engine, the temp listed indicates at what temp it will be fully open. the placement of the jiggle valve would have no effect on that. Now here come the arguments.
 
When I bought my truck Feb 2016 and went to replace the thermostat, the jiggle valve was in 6pm position. When I put the new thermostat in, I placed it in 12pm position. Shortly after this, I bought a Scangauge and noticed temps were ~207F. I then re-positioned the new thermostat with jiggle valve down at 6pm position, now @ 188-191F. Unfortunately I don't know what the temps were BEFORE i replaced the original thermostat but I can confirm the jiggle valve WAS at 6pm.
 
Your fine. Denso is OEM supplier. If you start breaking 210* and keeps climbing than you have an issue. But 210* in the summer with AC on in traffic is normal.

Yes you could drop about 10* flipping the thermostat but in the winter I like the warmer air.
 
Thanks for all the replies. I'll probably switch it to 6 just for peace of mind but interesting to hear multiple experiences. I deal with hot days way more than cold days so ac is on a lot. A 10deg drop would be nice
 
I've had two trucks with the 3.4L engine. A tacoma that I bought new in 04 and now an 02 4Runner. My old tacoma always ran temps in the low 190's. When I bought my 4Runner I noticed that the temps were consistently around 207. Checked the thermostat (which was replaced by a Toyota dealership during a timing belt replacement) and found the jiggle valve in the 12 o'clock position. I flipped it over to the 6 o'clock position and now I see temps around the 190 mark again. Moral of the story, the engine should be operating around 190 from my experience and dealers suck.

I'd take it back, ask them where the jiggle valve is supposed to be placed, and upon their answer, I would show them the FSM and ask if they always perform repairs improperly and kindly request that they fix your ride correctly.
 
I never worry about the position of the jiggle valve.

I too in west TX and even towed my car 600 miles on a dolly in August with the temperature needle sitting just below half-mark. The IR thermometer gives 83 Celsius (approx: 181 F) on the top coolant outlet located on the engine.

Did you burp the system well? Did you clean the AC condenser fins? Is the fan clutch functioning? and is it OEM or AISIN? These are the main factors that will play the major role in cooling.

Finally, do you run the AC at full speed all the time? On summer, this will cause the compressor to run full time heating the ac condenser thereby heating the radiator. I use the full speed for the first 10-15 minutes and then switch it to 2 or 3.
 
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I still can't believe this is even a debate.

Why would it be acceptable to put in an 82*C (180*F) thermostat on an engine then regularly see >200*F temps? The engine was designed for 180*F water (inlet) temps. That's what it should run. Installing the thermostat correctly achieves this. End of story.

-Charlie
 
Haynes manual says jiggle valve at 12 o'clock, Toyota FSM say 6 o'clock. I would go with the FSM. Btw mine was installed at 12 then i switched it to 6 and now runs 10 degress cooler.
 
Did you burp the system well? Did you clean the AC condenser fins? Is the fan clutch functioning? and is it OEM or AISIN? These are the main factors that will play the major role in cooling.

Finally, do you run the AC at full speed all the time? On summer, this will cause the compressor to run full time heating the ac condenser thereby heating the radiator. I use the full speed for the first 10-15 minutes and then switch it to 2 or 3.

I'll be sure to ask that they burp it, and I'll check before I get on the road. I'll also look at the fan clutch. As for the a/c, I do like it cold but I have the limited digital temp controls and usually leave it at 1-2 "bars" out of 5 at 68-70deg. I appreciate all the feedback!
 
Update: went to dealership, had them top it off with coolant (reservoir was empty @ cold) and burp the system. Said fan clutch was good, but swore the thermostat was supposed to be at 12, according to their master mechanic (aka older, set in ways imo). Didn't have an answer when i showed them the FSM print out that clearly says "place jiggle valve downward", and didn't want to spend all day there so I hit the road. 9 hours straight to Tulsa, coolant stayed around 203° with low a/c, only rising (208-210) in Austin and Dallas stop/go traffic. Going to track temps in typical city driving here, and then switch the thermostat around and make note of any changes. Thanks for indulging my rants!:thanks:
 
Update 2: Back home, city driving shows the same range of temps (203-208°). Time to properly clock the thermostat!

I ordered a Lisle spill-free funnel, as soon as that arrives I'll flip the thermostat around and properly burp the replaced coolant, check the temps again.
 
The thermostat position will not make a difference. My OEM one installed when the car was brand new was at the 12 o clock position. I installed my new t stat in the 12 o clock position when I did the timing belt. According to my scangauge the temp is always around 188 to 195. Ive only seen it get to 200 once in heavy traffic when it was 110 out. The valves purpose is to aide in removing air from the system. Its too small for any significant amount of coolant to pass through it. The temperatures have to do more with the percentage of coolant to water.
 
The topic has been so heavily debated with one clear cut answer that it really come down to a matter of opinion on the subject

Right on, I've seen posts where it made no difference and for others (and me personally) it did, so really the only way to find out is to actually try it and see. One thing going for the 6pm cult is the FSM which specifies the correct jiggle valve position as being "downward."
 
I'll play 6 o clock made a 10-12 degree change on mine for the cooler.

Now in all honesty if none of us had these obd II readers we wouldn't know the difference and would carry on like everything was normal.

But I'm a 6 o clock fan boy because we have neat tools to help us.
 

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