Why Does the Thermostat Jiggle Valve Position Make Such a Big Difference?

Joe Z said:
This subject really gets me thinking....maybe that little Jiggle valve is like the jiggle valves on grandmas old pressure cooker....with it down and no bubbles it just gets water flow pressure, with it up there could be a lot of bubbles and it reacts to the sensor on the thermostat and maybe it doesn't fully open...
This is just a thought and a thought only but there's got to be a reason it works for many??
Click to expand...

The temp sensed by the thermostat being influenced by it's orientation makes sense. You might be on to a logical reason for engines running a little cooler with the jiggle valve at 6:00!
 
jhfleet said:
The temp sensed by the thermostat being influenced by it's orientation makes sense. You might be on to a logical reason for engines running a little cooler with the jiggle valve at 6:00!
Click to expand...

Another thought, who knows..... with the jiggle up maybe it aerates the water a bit and sends more of a tiny bubbly mist throughout the system affecting temperature.

When i pull my Tstat out (hopefully a long time from now) i'm going to try the down position
 
HiluxSurf SSR-G said:
What is the function of the 'jiggler valve' on a thermostat? (Engine Overheating)
Click to expand...

On my original research for the purpose of the jiggle valve, I read that thread and others stating it's for getting trapped air out of the system. But, if that were the case, why would we be positioning the jiggle valve pointing downward. Air rises, right? It's well-documented that the 6 o'clock position for the jiggle valve in our rigs can drop coolant temps 10-15 degrees.

I think the best theory I've heard so far is it has to do with the flow characteristics of the coolant when it comes out of the block and hits the thermostat. Maybe the strongest flow is towards the bottom and the jiggle valve helps the thermostat open sooner in this position.
 
For grins I looked into the jiggle valve orientation for the Toyota cars: Avalon/Camry with a V6. And it says to put it vertical! I understand it's a different engine and these thermostats are located at the rear of the valley of the engine, almost totally opposite of the 3.4 trucks. But there's no way the flow of coolant is substantially dissimilar from an engineering standpoint...

Thermostat still faces towards the engine and is located on the lower radiator hose. The only option at this point has GOT to be with the aeration/fluid dynamics theory since our t/stats are so close to the water pump. I will ask some Toyota techs I know and see if there are any more ideas.

Quite perplexing.

On another note, [MENTION=115590]StreetCreeper[/MENTION] I heard if you run WITHOUT coolant altogether you won't be worrying about a damn jiggle valve.
 
mtbtim said:
On my original research for the purpose of the jiggle valve, I read that thread and others stating it's for getting trapped air out of the system. But, if that were the case, why would we be positioning the jiggle valve pointing downward. Air rises, right? It's well-documented that the 6 o'clock position for the jiggle valve in our rigs can drop coolant temps 10-15 degrees.

I think the best theory I've heard so far is it has to do with the flow characteristics of the coolant when it comes out of the block and hits the thermostat. Maybe the strongest flow is towards the bottom and the jiggle valve helps the thermostat open sooner in this position.
Click to expand...

Or, maybe the jiggle valve orientation itself has no effect on the operation of the system. Maybe the temp sensing wax pellet in the stat needs to be oriented a certain way. If so, the jiggle valve location might serve only as a handy indicator to ensure the rest of the thermostat is properly oriented. (I don't really think so, but it's possible!)
 
He is on to something !

On another note, [MENTION=115590]StreetCreeper[/MENTION] I heard if you run WITHOUT coolant altogether you won't be worrying about a damn jiggle valve.
Click to expand...

Seems like an early 70's VW Beetle we had for a backup work vehicle many moons ago got along just fine without coolant ...

Magic !

:rofl:

Britt
 
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CC Silver said:
Seems like an early 70's VW Beetle we had for a backup work vehicle many moons ago got along just fine without coolant ...

Magic !

:rofl:

Britt
Click to expand...

Also my old man's super fun to drive, but much maligned, '64 Corvair with a flat-six boxer air-cooled rear engine. No dang coolant, evah!
 
Just changed my thermostat and...

1998 4runner limited w 3.4, I just changed my thermostat and the new one doesn't have a jiggle valve, but the old one did. Did I get sold the wrong thermostat ?
 
mtbtim said:
Howdy Everyone,

Probably not the most exciting thread like somebody showing pics of their sick mods on their 3rd Gen but I'd really like to find an explanation out there of why the jiggle valve positioning can make such a big difference in coolant temps (around 10-15 degrees).

The FSM says the jiggle valve must be pointed downward at the 6 o'clock position. Some people with the Haynes manual for their trucks says it's supposed to be placed at the 12 o'clock position. Some on this forum have recently replaced their thermostats, including myself, and found the jiggle valves in different position. [MENTION=115590]StreetCreeper[/MENTION] found his at the 1-1:30 position. I found mine at the 3 o'clock position. I placed my new one at the 6 o'clock position and nothing changed. My coolant temps were around 190 before and that's where they are now. [MENTION=136650]DK327[/MENTION] placed his at 12 and found he was running in the 200's for his coolant temp. When he switched it to 6, his coolant temp dropped to the standard 190 range where most of us run at.

I did some more reading on thermostats and the function of the jiggle valve and found an interesting statement from this Australian Radiator company.

Here's the link to the website:
ARE Cooling

And a quote:
"All High-Flow Thermostats are fitted with a jiggle pin that enables the system
pressure to be stabilised so that the valve opens easier. The jiggle pin also
allows air pockets to move past the Thermostat and the temperature to be
regulated more efficiently. Fitting High-Flow Thermostats will allow your
vehicle cooling system to operate more efficiently."

I already knew the jiggle valve helped remove air pockets so it would prevent an air lock but this new claim that it enables the system pressure to be stabilized so that the valve opens easier is something I didn't know.

But what is still hard to understand is why the position of the jiggle valve makes such a big difference. Is it possible the coolant piping leading to the thermostat doesn't actually fill completely to the top so a jiggle valve placed at the 12 o'clock position isn't going to be as effective? I would think since the system is pressurized the piping would be full. Could it be something with gravity?

Hopefully some of you mechanical engineering types will be able to explain this because I'd really like to understand what is happening that makes such a big difference with the positioning of the jiggle valve.
Click to expand...

The sole purpose of this "valve" is to assist in any trapped air behind the thermostat to leave the system. The air will most definitely leave, I know techs who cut the valve out. Any difference in temp is a mystery, although the AM t stats usually run 10 to 15 degrees hotter than the OE t stats, there's food for thought.
 
I don't really have an answer to the original question, but I will say that I recently bought a 3rd gen and when I installed my scan gauge found that my temps were consistently between 204 and 210. Having had a Tacoma with the 3.4L for over ten years and never seeing a temp over 197, I wasn't comfortable with the 210 temps I was seeing. Removed the thermostat housing, found the jiggle valve at 12 o'clock (last replaced by a Toyota dealer during a t belt change btw), turned thermostat 180 degrees to have the jiggle valve at the 6 o'clock position, now my average temp is 186. I can't explain it, but the proof is there for me...
 
Nate_GB said:
I don't really have an answer to the original question, but I will say that I recently bought a 3rd gen and when I installed my scan gauge found that my temps were consistently between 204 and 210. Having had a Tacoma with the 3.4L for over ten years and never seeing a temp over 197, I wasn't comfortable with the 210 temps I was seeing. Removed the thermostat housing, found the jiggle valve at 12 o'clock (last replaced by a Toyota dealer during a t belt change btw), turned thermostat 180 degrees to have the jiggle valve at the 6 o'clock position, now my average temp is 186. I can't explain it, but the proof is there for me...
Click to expand...

You and many others like you have experienced the same exact thing. What exactly is happening with the change in jiggle valve position to affect the temperature that much is a mystery. Like [MENTION=148927]Toyotayoda[/MENTION], i have also read that the jiggle valve was there for any trapped air to escape, but if that were the case, wouldn't it make more sense for it to be at the 12 o'clock position since air rises?

Anyway, jiggle valve at the 6 o'clock position is the way to go for our rigs.
 
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humboldtrunner said:
So I did get sold the wrong thermostat ? The one I just put in does not have a jiggle valve
Click to expand...

Yes you did. It should have a jiggle valve. I'd recommend replacing it with one you get from a Toyota online parts seller like Camelback Toyota or just go to your local dealer and get one. It's not an expensive part so theirs no reason to go aftermarket. Make sure to put the jiggle valve at the 6 o'clock position.
 
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