Overflow Tank

[StockyStock]

Couldn't find a thread about this specifically so here goes

BACKGROUND

Bought a Mishimoto rad 2 years ago to replace my leaky OEM. Leak was a drop here or there, mostly came out during pressure test. Didn't install the Mishimoto until this weekend.

Turns out, the overflow nipple isn't cast in and the OEM cap doesn't fit. Ordered a cap but more importantly,

IS THE OVERFLOW TANK NECESSARY? (All capsing to make it an easier skim) I'm not trying to buy another or drain all the coolant again for a bit. Hoping this will work out. Is the overflow tank more an emergency thing Toyota made for the odd extreme temps case or is it absolutely necessary/will break something running it like this?

TIA

 

[alumarine]

It's needed.
It's not just Toyota that has used them for the last 40 years.
How Does A Radiator Coolant Overflow Tank Work? [2022 Guide]

 

[StockyStock]

I get how it works. I'd like to note I've literally never seen coolant in my overflow tanks at operating temps so I was wondering how often it even comes into play.

I'll have to contact Mishimoto and see if they're dumb or if it was an unfortunate mess up that happened 2 years ago with casting

 

[jgue467]

... at operating temps so I was wondering how often it even comes into play. ..

Once it gets to 'normal' operating temps in warmer weather it should pressurize, reach the limit and emit any excess (just a few ounces or so) into the recovery tank, kinda normal in every auto I've had, some emit more than others...

If not Full and/or has air, perhaps that would be one reason a system would not emit any into the recovery tank...

 

[brillo_76]

If your not seeing antifreeze coming and going from your overflow tank. You have a coolant issue. My 1998 used to not pull coolant from the over flow tank. Until I found the seep leak at the water pump. Once I fixed that leak. Low and behold the system worked like should.

I suspect you have a seep and your system or radiator cap isn't functioning properly.



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[Devbot]

It's not just Toyota uses them, everyone does because the amount of free space in radiators has greatly diminished over the century. If your radiator had enough room to compensate for expansion then no you wouldn't, however in the vast majority of cases that isn't the case even with aftermarket. Some might argue that they aren't necessary, and as long as it's full while it's hot then it's alright - however the problem with this logic is during a cold start when the coolant temps lower and the level recedes again, it can fall to a point where the system can have air induced into it during it's initial cycling and engine turn over. Get enough air and you'll begin to overheat, which will push out even more coolant, etc. etc.
Obviously this will vary from vehicle to vehicle/radiator to radiator, but as a general rule of thumb an overflow tank will never hurt. Look at it as cheap insurance. I suppose you could mess about with capacity levels, getting it to operating temp and all that to see if it was really necessary, but if you were that curious really i would just call the manufacturer first and see what they say. Chances are they'll tell you to run one if the vehicle came with one.

 

[Bad Luck]

I get how it works. I'd like to note I've literally never seen coolant in my overflow tanks at operating temps so I was wondering how often it even comes into play.

I'll have to contact Mishimoto and see if they're dumb or if it was an unfortunate mess up that happened 2 years ago with casting

You should have coolant in your overflow tank to at least the minimum cold line and it should raise in level if your cooling system is functioning correctly. It’s a necessary part of the cooling system since there is no expansion reservoir

 

[19963.4lsr5]

Until you figure it out don’t fill your Rad all the way to the top. Leave a 1/2” air gap so the water can expand.


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[StockyStock]

I'll be waiting for a new Denso to arrive and bumming cars for now. Not worth a risk. My other car decided to drop all clutch fluid over night so I'm waiting on parts for that as well