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

[humboldtrunner]

Jiggle valve

Thank you much for the replies. Although the name itself sounds silly, it's function is definitely not. A jiggle valve sounds like something a girl with FLBP would need !:girl::girl:

 

[eliasb11]

My guess is that it has less to do with with allowing air through than neutralizing a fluid pressure differential across the thermostat. The 12 o'clock placement would make the most sense if the primary goal of the jiggle valve was to allow air past, but the 6 o'clock position suggests that allowing fluid flow is probably the more important function. This means that thermostat will be opening and closing solely as a function of fluid temperature and not affected by a pressure differential built up across a closed thermostat

 

[pauldub]

I have a Scan Gauge and found there was absolutely no difference in temp with the jiggle valve at 12:00 or 6:00. I'm suspicious that the FSM is simply in error. In my nearly 40 years of engineering experience at a local airplane company, there were many times that the guys who wrote the maintenance manuals made a big mess of things.

 

[mtbtim]

I have a Scan Gauge and found there was absolutely no difference in temp with the jiggle valve at 12:00 or 6:00. I'm suspicious that the FSM is simply in error. In my nearly 40 years of engineering experience at a local airplane company, there were many times that the guys who wrote the maintenance manuals made a big mess of things.

I agree manuals can be wrong at times. I've caught several mistakes in my 2000 manual. But, this is not the case in this situation. I've personally seen a change in temperature with a switch of the jiggle valve position on 2 different 3rd Gens and there's tons of others who've experienced the same thing on this forum. Why it made no change for you i don't know. For some reason you're an exception to the rule. I think there's some type of voodoo going on with these jiggle valves.

 

[AntleredRuin]

Just a thought: in addition to the earlier post mentioning that 12 may actually cause any trapped air to aerate the coolant moving through the system.
We know that air rises, so what if the valve at 6 helps 'trap' excess air at the tstat? That way, it won't continue to cycle through the system.

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[SaulG]

https://imgflip.com/memegenerator

Cooling system is pressurized :der:

 

[slomatt]

I have a Scan Gauge and found there was absolutely no difference in temp with the jiggle valve at 12:00 or 6:00. I'm suspicious that the FSM is simply in error. In my nearly 40 years of engineering experience at a local airplane company, there were many times that the guys who wrote the maintenance manuals made a big mess of things.

Using a Scan Gauge I've measured a 10 degree lower temperature having the jiggle valve at 6:00 vs having it at 12:00. When I had my timing belt changed they put the jiggle valve at 12:00 and I immediately noticed my truck ran ~10 degrees hotter than normal, after switching it back to 6:00 the temperature went back to normal.

- Matt

 

[poopypants]

post revival....

I've got to thinking... The jiggle valve is of function at only one point in time, when the thermostat is closed.

Standard operating temps are well above the temp at which the thermostat actually opens by about 15-20°... This means the operating temp of the vehicle would NOT be effected by the jiggle valve, per se, considering the thermostat is open and the function of the jiggle valve is only effective when it's closed....

It's not about the jiggle valve orientation at all, that's just an easy and well known thing to reference...

... it's all about the larger opening of the thermostat being at the top of the tube during normal operating temps, therefore allowing the hottest section of the hose to flow the fastest, as opposed to deflecting off the jiggle valve and flat facing, circulating backwards and down, to then make it through the large thermostat opening!

This would EASILY explain why it is that "Putting the jiggle valve at 6 o’clock" aka "putting the water flow opening at 12 o'clock", makes a difference in peak OPERATING temp/cooling efficiency.

 

[jmansfield]

Had to revive...just experienced a ~20 degree swing...

I recently bought a 98 runner (5vz, automatic) and was seeing coolant temps in the mid 200s. After checking other folks' coolant temps and seeing I still had the original radiator on the car, I decided I'd replace the radiator, put in the red coolant (previous owner had green) and replace the thermostat. Well I did all that and I was still reading mid 200s, even got 210 at one point (all freeway driving). Here I am, new radiator, toyota red long life, new thermostat, and I'm hitting the same temps, if not higher, what gives?

Dig around the forums and I come across the jiggle valve. Hm, didn't notice the orientation when I installed it. Well, I took off the thermostat this evening, I had originally installed it in about the 11;30 position. Flipped to 6 o'clock, and BOOM!! Now I'm in the upper 180s/lower 190s. Nearly a 20 degree swing. Unbelievable

 

[mtbtim]

Had to revive...just experienced a ~20 degree swing...

I recently bought a 98 runner (5vz, automatic) and was seeing coolant temps in the mid 200s. After checking other folks' coolant temps and seeing I still had the original radiator on the car, I decided I'd replace the radiator, put in the red coolant (previous owner had green) and replace the thermostat. Well I did all that and I was still reading mid 200s, even got 210 at one point (all freeway driving). Here I am, new radiator, toyota red long life, new thermostat, and I'm hitting the same temps, if not higher, what gives?

Dig around the forums and I come across the jiggle valve. Hm, didn't notice the orientation when I installed it. Well, I took off the thermostat this evening, I had originally installed it in about the 11;30 position. Flipped to 6 o'clock, and BOOM!! Now I'm in the upper 180s/lower 190s. Nearly a 20 degree swing. Unbelievable

There have been people that don't believe the orientation of the thermostat can have such a difference in the coolant temps. I've told those people, you don't have to believe me. Switch the orientation of the thermostat, and using a scan gauge or phone app, you'll see the difference in person and become a believer. I think [MENTION=136095]poopypants[/MENTION] above might have uncovered the secret why the thermostat position has such an effect on the temp. But, then again, maybe it's just jiggle valve magic.

People have also commented saying, "But, the Haynes manual says to put the jiggle valve at the 12 o'clock position." I politely tell them the Haynes manual is full of shit and the Toyota FSM is one they need to follow.

Then there's people that say it's not a big deal to run 10+ degrees hotter all the time. Over the short term, maybe they are right. But, over years of heating and cooling cycles, maybe running 10 degree cooler could have made the difference between a cracked head or blown head gasket happening at 250k as opposed to 450k.

 

[19963.4lsr5]

For the record when I did the timing belt job on the 96 I did what you normally do with a jiggle valve and put it strait up and my temps driving that engine in my 97 project were always 185-188. Then of coarse the engine died from what looked like a previous injury I wasn't aware of


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[jmansfield]

There have been people that don't believe the orientation of the thermostat can have such a difference in the coolant temps. I've told those people, you don't have to believe me. Switch the orientation of the thermostat, and using a scan gauge or phone app, you'll see the difference in person and become a believer. I think [MENTION=136095]poopypants[/MENTION] above might have uncovered the secret why the thermostat position has such an effect on the temp. But, then again, maybe it's just jiggle valve magic.

People have also commented saying, "But, the Haynes manual says to put the jiggle valve at the 12 o'clock position." I politely tell them the Haynes manual is full of shit and the Toyota FSM is one they need to follow.

Then there's people that say it's not a big deal to run 10+ degrees hotter all the time. Over the short term, maybe they are right. But, over years of heating and cooling cycles, maybe running 10 degree cooler could have made the difference between a cracked head or blown head gasket happening at 250k as opposed to 450k.

Absolutely agree with the last part. Could be much sooner than 450k that that issue would've came up. I dropped from 204-208 to 186-188, literally 20 degrees driving freeway in California. So flat ground, 70 degrees out. All it might've taken was a couple trips in the summer in the high desert up a nice grade, car pilled full of junk, that could be the difference between the warped head and not right there.

I think reorienting the thermostat is the single most important thing I have done for my car thus far.

 

[gamefreakgc]

I'm also a believer. I did a timing belt on mine back in July, so I thought what the heck, I'll try flipping it. Was previously at the 12 position. I would get high 170's to mid 180's on highway driving (cooler thermostat via supercharger package).

Soon after I tested it was in the low 170's, about a 10 degree drop. Under cooler weather it's in the low 160's... which is almost getting too cold lol!

 

[JKD]

When I did my own timing belt I read this thread and debated positioning.

In the end I went with what the book said (and what the original OEM one was at after the Toyota Dealer did first timing belt) and that was 12 o'clock. (ish)

Funnily enough my temperature dial went to exactly the same place it always has for the entire life of the car, 188k miles now and I won't worry about it until the next time I need to change something on the cooling system - i.e. it's not worth the hassle of draining the system, for!

 

[mtbtim]

When I did my own timing belt I read this thread and debated positioning.

In the end I went with what the book said (and what the original OEM one was at after the Toyota Dealer did first timing belt) and that was 12 o'clock. (ish)

Funnily enough my temperature dial went to exactly the same place it always has for the entire life of the car, 188k miles now and I won't worry about it until the next time I need to change something on the cooling system - i.e. it's not worth the hassle of draining the system, for!

Well, you need to know that the factory temperature needle gauge will not show a difference of 10-20 degrees. By the time you see your needle rising, your engine temp is pretty far up there. For this reason and to read other information from your vehicle ECU, I recommend using a scan gauge tool or a bluetooth reader sending information to a phone app like Torque Pro. You can catch an issue with your cooling system much quicker.

If you're jiggle valve is currently at the 12 o'clock position, you are running at least 10 degrees hotter. I don't know what book you're reading but the Toyota FSM specifies that the jiggle valve point downward at the 6 o'clock position. And, it goes to show not even Toyota dealership mechanics know what the correct position is. I personally think it is worth the hassle to drain the coolant and get the thermostat in the correct orientation. You could drain the coolant into a clean container, remove the lower radiator hose, take off the (3) 14mm nuts for the water neck, get the thermostat in the correct orientation and put it all back together. Easy Peasy. But, if you want to wait 30-50k until your next scheduled coolant renewal, it's your engine and your choice.

 

[TheDurk]

When I did my own timing belt I read this thread and debated positioning.

In the end I went with what the book said (and what the original OEM one was at after the Toyota Dealer did first timing belt) and that was 12 o'clock. (ish)

Funnily enough my temperature dial went to exactly the same place it always has for the entire life of the car, 188k miles now and I won't worry about it until the next time I need to change something on the cooling system - i.e. it's not worth the hassle of draining the system, for!

Here is MY book:

 

[JKD]

Here is MY book:

Welp, I did this before I bought the FSMs. I found a diagram online and clearly mistook what I was looking at for the book. It was obviously not the the right one and am fairly sure the picture that came with the ASIN kit showed it 12 o'clock too...live and learn. :-/

If I get bored one day, I may do the switch out...almost contemplated it when I replaced the fan clutch.

10-20 would make a diff in the Summer of Cali for sure but as the truck is running fine and the temp gauge is right where it's at the whole of the trucks life then why take the risk..knowing my luck I'd not burp it properly.

 

[mtbtim]

Welp, I did this before I bought the FSMs. I found a diagram online and clearly mistook what I was looking at for the book. It was obviously not the the right one and am fairly sure the picture that came with the ASIN kit showed it 12 o'clock too...live and learn. :-/

If I get bored one day, I may do the switch out...almost contemplated it when I replaced the fan clutch.

10-20 would make a diff in the Summer of Cali for sure but as the truck is running fine and the temp gauge is right where it's at the whole of the trucks life then why take the risk..knowing my luck I'd not burp it properly.

Maybe you didn't read my last post. Your needle temp gauge on the dash isn't going to register a 10-20 degree change so saying your gauge is in the same spot doesn't mean anything. It is NOT a good gauge to show slight differences in temperature. Only a scan gauge or a phone app will show small differences in temperature. Trust me when I say you're running hotter than you need to be.

You now have the information in your hands. What you do with it is entirely up to you. You can say all you want that it probably doesn't make a difference but it's not hard to believe that it could make a huge difference in the longevity of your engine.

 

[JKD]

Maybe you didn't read my last post. Your needle temp gauge on the dash isn't going to register a 10-20 degree change so saying your gauge is in the same spot doesn't mean anything. It is NOT a good gauge to show slight differences in temperature. Only a scan gauge or a phone app will show small differences in temperature. Trust me when I say you're running hotter than you need to be.

You now have the information in your hands. What you do with it is entirely up to you. You can say all you want that it probably doesn't make a difference but it's not hard to believe that it could make a huge difference in the longevity of your engine.

I appreciate it, I do have an ELM ODB II device but the app I use is rubbish, need to get something going there.

Appreciate you and all the forums help.

 

[gamefreakgc]

Welp, I did this before I bought the FSMs. I found a diagram online and clearly mistook what I was looking at for the book. It was obviously not the the right one and am fairly sure the picture that came with the ASIN kit showed it 12 o'clock too...live and learn. :-/

If I get bored one day, I may do the switch out...almost contemplated it when I replaced the fan clutch.

10-20 would make a diff in the Summer of Cali for sure but as the truck is running fine and the temp gauge is right where it's at the whole of the trucks life then why take the risk..knowing my luck I'd not burp it properly.

Not worth pulling it all apart just to flip it around, if putting it at 12 o'clock was a big issue then we'd see overheating 4Runners all over the place. You are good, drive happy. Now, if later down the road you happen to work on the cooling system and have the lower coolant hose and housing off, sure, give it a try.