The position of the V6 thermostat / jiggle valve DOES make a temperature difference (-12°F for me)

I've read about the jiggle valve phenomenon for a while. I am a skeptic by nature, but there were WAY too many guys reporting a pretty big temperature difference to write it off. Plus, none of the guys making the claim had anything to gain by making it; they weren't selling a product and didn't stand to benefit in any way from saying what they said.

So, I did what in my opinion was a pretty controlled experiment. My commute to work is very consistent, so I recorded the engine temperature when I pulled into a parking spot at work several times by taking a picture of my Ultragauge as soon as I pulled the parking brake.

Last Saturday, I pulled the thermostat and noticed the jiggle valve was at 2 o'clock. I assume that the tech that did the timing belt at 90K reinstalled it in a random position. I put on a new gasket, reinstalled the same exact thermostat (not a replacement) with the jiggle valve at 6 o'clock, put the same coolant that I drained out back in and made no other changes.

Here are the Ultragauge images from several trips to work before the change, one trip home, and two trips to work after the change.

Trip to work #1, jiggle valve at 2 o'clock:



Trip home, jiggle valve at 2 o'clock:



Trip to work #2, jiggle valve at 2 o'clock:



Trip to work #3, jiggle valve at 2 o'clock:



Trip to work #4, jiggle valve at 2 o'clock:



OK, so are you convinced that my truck runs at 199.4°F yet? I hope so.

Trip to work yesterday morning, jiggle valve at 6 o'clock:



Trip to work this morning, jiggle valve at 6 o'clock:



What I think has been too much of a focus in the arguments regarding this is the jiggle valve itself. Is it really the jiggle valve that has anything to do with the difference in temperature? Or is it merely the position of the thermostat itself, and the jiggle valve just happens to be what the FSM uses as a reference to make it easy for the installer?

Perhaps with the thermostat in this position, it creates the highest flow and the least turbulence as water rushes through, regardless of the jiggle valve.

Here's another thread on the topic that is pretty convincing.

http://www.yotatech.com/f2/5vz-fe-running-warm-after-timing-belt-pictures-pleasure-249481/

 

Hi bumping this old thread because I had a situation similar. Once I got a scan gauge and started monitoring temps and comparing to other 5vzfe friends I was running about 10-15 degrees warmer. It would run 198 then when I would come to a stop it would go to 200-202. I flipped the thermostat cleaned everything up installed it at 6 o’clock 2 gallons of Toyota red. She now runs 190 and occasionally hits 191-192 at a stop so I am very happy with the results. Oh yeah jiggle valve was at 11 o’clock when I pulled it.

 

My Taco was running 195-200 degrees consistently and when I pulled the thermostat it was at the 12 o'clock position, done by me since I didn't read the FSM when I changed it originally. I flipped the thermostat to the 6 o'clock position and now runs consistently 186-188 degrees. It did get up to 190 when we had the 115 degree heat wave here but cooled down fast as I got moving.

 

Yeah it’s pretty much impossible detect the difference with the stock analog gauge.

 

Oh I use a Scanguage 2 on my truck.