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is this really an overflow tank?

J

jmg222

NAXJA Forum User
NAXJA Member
Location
US
still working through my overheating problem, and noticed something that I never bothered to question before (I dropped the 350 in my xj over 12 years ago, I didn't do all the work)... what the heck is this? It's clearly supposed to be an overflow tank, but it looks like a charcoal canister... debating if I should replace it with a real overflow. Anyone ever see anything like this? (I'm not saying this is contributing to my overheating issue, put this in the category of what the hell was I thinking when we put that in)

20zzds9.jpg

a5c2v.jpg
 
blakews2217 said:
Generic overflow tanks come from the radiator cap
Click to expand...

It is connected to the radiator cap (look at the stainless steel line going to the fill cap in the pictures). It's weird that there's no drain.. I don't want to replace it if it's fine, just loks more like a charcoal canister than an overflow to me.
 
Well I'm a bit stupid. If it were an overflow it should have a vent and an overflow port. I'd see if it opens and see if a hose goes to the bottom of the bottle


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ok-- I should've been a little clearer. There's only one hose going from the coolant fill to the "can". So, it's not recirculating (if it were, I agree, no drain. But if it were recirculating, ovciously would need a return hose). Since there's only a single hose, it's set up as an non-recirculating overflow... in which case, shouldn't it have a drain and an air vent?

This is a relatively minor issue. I don't have any leaking or overflowing antifreeze anywhere, so I may just put it in the "don't fix it if it ain't broke" category. I can't imagine this has anything to do with my overheating issues either.
 
blakews2217 said:
Well I'm a bit stupid. If it were an overflow it should have a vent and an overflow port. I'd see if it opens and see if a hose goes to the bottom of the bottle


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Click to expand...

it doesn't open-- it's completely sealed, no vent. weird.
 
by the way, if I replace it with a standard overflow canister (jeggs has some nice chrome ones :) ) do I have to worry about introducing air into the system?
 
As long as the cap stays on it will back purge itself. The way that cooling system works with the tank is when it gets warm the rad cap vents pressure ( as coolant) to the tank. When it cools it creates a vacuum and sucks the coolant back in. As long as you keep fluid in the tank it should be fine.


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blakews2217 said:
As long as the cap stays on it will back purge itself. The way that cooling system works with the tank is when it gets warm the rad cap vents pressure ( as coolant) to the tank. When it cools it creates a vacuum and sucks the coolant back in. As long as you keep fluid in the tank it should be fine.


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Click to expand...

that's what I thought, but the overflow tank I got from jeggs (and pretty much all others I've looked at) have a fitting at the top for the overflow line, a drain at the bottom, and a vent hole at the top. overflow coolant will go into the canister, but I don't see how it gets sucked back in-- there's nothing but air at the top of the overflow tank.

In the "tank" I have in the pictures above, there's no vent hole at all, I don't see how coolant is supposed to flow into it.

Again, not a huge deal, worst case I don't have any overflow and I'll just spray fluid if the pressure exceeds cap pressure, but I'm thinking that replacing the canister with a standard overflow will cause the system to suck in air.
 
It will not if there's coolant in the tank. If you're looking for a new one, it must be recirculating. If not, it's a catch can. Jegs had some little stainless ones that looked nice, used one on my mustang.
 
jmg222 said:
that's what I thought, but the overflow tank I got from jeggs (and pretty much all others I've looked at) have a fitting at the top for the overflow line, a drain at the bottom, and a vent hole at the top. overflow coolant will go into the canister, but I don't see how it gets sucked back in-- there's nothing but air at the top of the overflow tank.

In the "tank" I have in the pictures above, there's no vent hole at all, I don't see how coolant is supposed to flow into it.

Again, not a huge deal, worst case I don't have any overflow and I'll just spray fluid if the pressure exceeds cap pressure, but I'm thinking that replacing the canister with a standard overflow will cause the system to suck in air.
Click to expand...

You sure there isn't a line inside the tank he goes from the fitting to the bottom...so it can over flow INTO the tank, and also suck fluid back to the system ??
 
Boostwerks.com said:
That is a catch can, not a recirculating overflow.

It will dump coolant into the can when hot, and then suck back in air when cold.

You need a recirculating overflow to prevent air getting into the system.
Click to expand...

Isn't that a recirculating tank then? I have a generic Dorman tank on my small block XJ.

The one I had was a recirculating sealed tank with the hose inside. I have since upgraded.

tank.jpg
[/URL][/IMG]
 
Boostwerks.com said:
That is a catch can, not a recirculating overflow.

It will dump coolant into the can when hot, and then suck back in air when cold.

You need a recirculating overflow to prevent air getting into the system.
Click to expand...

yeah, tjhat's what I thought. But without a vent hole, how is coolant even making it into the can? it's completely sealed.
 
jmg222 said:
yeah, tjhat's what I thought. But without a vent hole, how is coolant even making it into the can? it's completely sealed.
Click to expand...

The air in the can can compress. Coolant will find its way in there when the engine warms up and air will be pulled back into the system when it cools. This is why recirc tanks will have the inlet on the bottom along with a vent on the top. Its also why you need to keep them roughly half full at all times to prevent air from getting sucked into the system
 
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