2G coolant overflow tank how it works

[Allen2g]

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newbie question but how exactly does our coolant tank works, is it simply a overflow or does it pull coolant back into the system when needed? Currently have a monster can as an overflow, not sure if i should just keep it or go back to oem

 

[Kryndon]

Ever notice that the OEM reservoir cap also has a hose going almost to the bottom of the thing? That's not only so it doesn't let air back into the system, but also so it can pick up some coolant when needed. During the different cycles of engine operation and temperature, the coolant level changes (like increased RPM for example). Also it can change during Winter/Summer, cold/hot etc.

If you only let it flow out but not back in, you'll end up permanently removing coolant from the system and it will overfill the Monster bottle. However, if you put the same type of hose going from the top of the monster can to the bottom, it should theoretically work as the OEM reservoir, just maybe have smaller quantity (which again might cause some overflow problems). Also, I guess that little hole on the top is your breather/vent hole. If any coolant needs to overflow, it may end up leaking from there.

So really, just put the stock reservoir back on. I know it looks ugly when it fades into that yellow burnt plastic, but if you really want to, maybe paint it black but leave the area between FULL - LOW unpainted so you can keep an eye on the level. Or buy an aftermarket aluminium unit, which looks much nicer (or make it yourself if you can weld).

 

[Allen2g]

Ever notice that the OEM reservoir cap also has a hose going almost to the bottom of the thing? That's not only so it doesn't let air back into the system, but also so it can pick up some coolant when needed. During the different cycles of engine operation and temperature, the coolant level changes (like increased RPM for example). Also it can change during Winter/Summer, cold/hot etc.

If you only let it flow out but not back in, you'll end up permanently removing coolant from the system and it will overfill the Monster bottle. However, if you put the same type of hose going from the top of the monster can to the bottom, it should theoretically work as the OEM reservoir, just maybe have smaller quantity (which again might cause some overflow problems). Also, I guess that little hole on the top is your breather/vent hole. If any coolant needs to overflow, it may end up leaking from there.

So really, just put the stock reservoir back on. I know it looks ugly when it fades into that yellow burnt plastic, but if you really want to, maybe paint it black but leave the area between FULL - LOW unpainted so you can keep an eye on the level. Or buy an aftermarket aluminium unit, which looks much nicer (or make it yourself if you can weld).

Holy shit, i feel dumb . But on my defense, ive never actually looked into a stock tank, when i got the car this can was already the tank . i simply guessed it was just an overflow seeing there was a hose from the neck then an overflow hose. I never knew there was actually a hose inside it which took coolant and prevented air. TY FOR THE INFO.

 

[Allen2g]

Yeah im going to purchase a oem res tank or make my own.

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maybe something like that

 

[Kryndon]

Hey, it's better that you asked and thought about it rather than completely ignore it. We learn as we go .

If you don't have access to the stock reservoir and want to make something custom, let me know and I can measure the stock quantity, height, width and the size of the inner hose. With those specs maybe you can make something yourself. A small bottle may be too small.

 

[Allen2g]

That would be great!! I prolly just need to know the amount of coolant the tank can hold so i can find a bottle close to the same size, also the amount the full/low line are. So i can mark that onto the bottle.
If you dont mind that is^^

 

[rEclipserGST]

Keep in mind that whatever container you use needs to be resistant to 200 degree temperatures.

That gatorade bottle won't last. Do not ask me how I know.

 

[iaintmaci]

I had to replace the tank on my Spyder. I had one of these I got used and it works perfect.

https://www.mishimoto.com/aluminum-..._42falV-snRD0_uVhSwXGdhDHAME_mURoCaLsQAvD_BwE

I was able to open a hole up on the mounting bracket a little, and now it just slides over the mounting stud on the top passenger side of the rad. I have put several thousand miles on it with no issues.

 

[Allen2g]

Keep in mind that whatever container you use needs to be resistant to 200 degree temperatures.

That gatorade bottle won't last. Do not ask me how I know.

seems youve had some experience . But no ill probably get something different and put it somewhere not too hot

 

[Allen2g]

I had to replace the tank on my Spyder. I had one of these I got used and it works perfect.

https://www.mishimoto.com/aluminum-..._42falV-snRD0_uVhSwXGdhDHAME_mURoCaLsQAvD_BwE

I was able to open a hole up on the mounting bracket a little, and now it just slides over the mounting stud on the top passenger side of the rad. I have put several thousand miles on it with no issues.

Mishimoto, alrdy sounds expensive ahaha. Im just going to fab my own

 

[rEclipserGST]

Put it somewhere not too hot? You do realize the standing fluid will be there, but it will push HOT coolant INTO the overflow.

Do what you like of course.

 

[Kryndon]

@Allen2g Yo bud,

Sorry for the delay but I really was preoccupied with other stuff. But today I did some measurements of the stock overflow bottle. Hopefully they can be of some help to you. My ruler had inch measurements as well, but I really ain't used to measuring things in inches so I did most in millimeters. Shouldn't really be a prob tho. I'll attach a pic but also list the measurements further down for easier reading since I don't trust my handwriting on cardboard, . So, from top to bottom:

Overflow cap:
Diameter (outer) of big end - 12.8mm
Diameter (outer) of small end (from thermostat elbow to cap) - 8mm
Diameter (outer) of inside section - 8mm
Length of inside pickup hose - 240mm

Overflow tank:
Length (top) - 4 inches
Width - 3 inches
Height - 10 inches
Distance between LOW and FULL lines - 3 inches
Total volume of overflow tank - approx. 1 Liter (33.8oz)
Volume of (up to) LOW section - approx. 250 mL (8.45oz)
Volume of (up to) FULL section - approx. 450 mL (15.2oz)

That's all I got. Hopefully it will be useful to you or someone else.

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[JPenny]

I used this approach and it worked very well no overheating. Sometimes the can would shrink/suck in slightly but never enough to crease. Very easy to do if you have the original cap.

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Thank you for your time, Jason Penny

 

[Allen2g]

@Allen2g Yo bud,

Sorry for the delay but I really was preoccupied with other stuff. But today I did some measurements of the stock overflow bottle. Hopefully they can be of some help to you. My ruler had inch measurements as well, but I really ain't used to measuring things in inches so I did most in millimeters. Shouldn't really be a prob tho. I'll attach a pic but also list the measurements further down for easier reading since I don't trust my handwriting on cardboard, . So, from top to bottom:

Overflow cap:
Diameter (outer) of big end - 12.8mm
Diameter (outer) of small end (from thermostat elbow to cap) - 8mm
Diameter (outer) of inside section - 8mm
Length of inside pickup hose - 240mm

Overflow tank:
Length (top) - 4 inches
Width - 3 inches
Height - 10 inches
Distance between LOW and FULL lines - 3 inches
Total volume of overflow tank - approx. 1 Liter (33.8oz)
Volume of (up to) LOW section - approx. 250 mL (8.45oz)
Volume of (up to) FULL section - approx. 450 mL (15.2oz)

That's all I got. Hopefully it will be useful to you or someone else.

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Thank you!! Just saw this now, the full line is 15oz which is perfect, i got a gatorade bottle as an overflow due to not having much dsms arouns my area and shipping one would be like 45usd in just shipping which is not worth .
Heres the one i made, thoughts? Would it work like the stock one .

 

[Allen2g]

Also how would you go about properly filling our cooling system?
Fill the coolant overflow so no air gets in the system, then fill the neck till full, fill as needed as fluid goes down, when filled, fill overflow to full line?

 

[Kryndon]

I haven't tried it like that, but I fear it may want to crumple inwards when heat gets too much. Might be wrong... Personally I would try to replace that straight barbed fitting with one that goes off to the side. That way the line from the cap to the thermostat housing will be more horizontal. I'm sure they sell those fittings in "L" shapes with a 90 deg angle.

As for filling the system; pretty much what you described. But you need to have the car running during that process, and keep massaging the upper and lower rad hoses to burp any bubbles out. The rad cap needs to be left off during the entire process. Also you need to have your heater set to MAX heat and fan speed set to 4 and the knob turned on the defroster mode (which blows towards the windshield). That way you open up the heater core so coolant can flow through there, mix up, and get rid of any more bubbles. When the car is up to operating temp and no more air is coming out, and the coolant starts to more or less spill from the coolant cap, close it off and shut the car off. You're done. Just make sure you have coolant in the middle between the low and full lines on the overflow.

 

[Allen2g]

Is a 90 degree barb neccesary or just preference? I personally couldnt find a 90 degree so i just went with a straight pronably missed it.

& yes thank you! Im aware of how to properly fill systems just wanting to make sure aha

 

[iaintmaci]

Mishimoto, alrdy sounds expensive ahaha. Im just going to fab my own

Check out Ebay honestly. Im not one for liking to cheap out on anything anymore (I learned my lesson)m but there are some knock-offs on there that look pretty nice. Round. Square. Painted. Polished. All for 35 or less.