thermostat with 2mm Hole in it.

[Cristobal]

Two years ago I replaced the thermostat in the Avalon with an original equip Toyota one, I told the mechanic to snip off the little sliding hourglass shaped part as that will speed up things when I flush and refill the cooling system. The car is used in SoCal and I have had good results---the car takes a wee bit longer to warm up but still tops off at the same temperature on the dash gauge with is about 192 degrees my mechanic says. I figure the little hole will help if the thermostat ever sticks closed and the thermostat cycles a lot less. The engine will cool down a lot if I am going down a grade like Town Pass in Death valley in winter; there you coast for about 9 miles and can do 70 miles per hour the whole way. What do you think of this practice?

 

[JHZR2]

I want my engine to heat as fast as it possibly can. Hopefully the diameter of the open thermostat is the same hole or not. At that point it is a non-issue at operating temp. I wouldnt want to delay warmup.

They make fail-safe thermostats if that is what youre worried about. I wouldnt be very worried about this if I installed a tested thermostat.

 

[oilboy123]

I agree.
I want it to warm up as fast as possible. I have seen charts before on how fast cylinder walls wear with the engine at cool temps. For that reason I like to run stock temp range unmodified thermostats.

 

[mechanicx]

I think that little pin is called the jiggle valve. It should allow air to escape when filling the coolant system but keep coolant from circulating when engine is running to aid warm up. I would not modify it.

 

[mechtech2]

I'd leave the little valve in.
If your thermostat breaks, then fix it.
The slightly faster warm up is the immediate and day to day goal.

 

[SteveSRT8]

It is indeed a proven fact that cylinder walls wear faster at lower temps. Ford published some great research on this in HP books way back in the 60's.

But the 'cutoff' point is around 180, so as long as the cylinder walls are above/around 180 there will not be any unusual wear. Note that their data was all developed with old dino oils so it may be a moot point today.

Many cars experience dramatic improvements in performance with a cooler stat. It's an easy mod that can make a ton of difference on some platforms.

But I must agree that I still wouldn't want to increase the flow through a closed stat and thereby increase warmup time!

 

[another Todd]

I think it is fine. Some thermostats come with a hole and no "jiggle valve". The amount of water bypassing the thermostat through that tiny hole is negligable.

 

[SteveSRT8]

negligible for most cars but not all.

1.5 liter all aluminum motor in 30 below zero weather? Might be an issue.

7 liter v8? No problemo.

 

[morris]

the small hole was started by some Chrysler engineers that found that a new mfg that makes stats. the new co made the stat air tight, causing a air lock. so they would drill a 1/8 dia hole to releave the air lock. i got this info form Old Cars mag, back in the dark ages

 

[steve20]

a common mod on the GM LT1 engines from the 90's these engines have reverse colling and it was a common practice to drill 2 small holes in the T Stat to help purge the air when flushing


Steve