External radiator header tank

[TurboRA28]

Howdy all, yesterday I dropped off all my engine bits n pieces with the machiner and was having a good chat to him about the build up.

Anyhows.. He suggested running a header tank. Reckons it is a good addition to almost all setups.

I was trying to get the idea of it all.. What I did pickup was you put a cap on the radiator that isn't pressurised. The radiator overflow pipe goes to this external header tank, that has its own pressurised cap on it.

That makes sense.. But then seems this header tank has a return pipe that goes back into the coolant system somewhere?

Can anyone expand on my limited header tank knowledge?

I've tried googling it with not much detailed results..

Cheers
Joel

[Toobs]

Basically its just an overflow system that can be pressurised.

The tank would usually be all metal so as to handle the pressure and will have its own radiator cap on it... it only has one combination inlet / outlet at the bottom of the tank and should be able half full of coolant.
Like the overflow system it will fill with hot coolant and return colder coolant... it just keeps the hottest coolant away from the radiator.

The Ford XR's have these as standard from at least the AU's but their tanks are made from a heavy duty plastic not metal... its not so easy to custom make tanks in this sort of plastic which is why most aftermarket setups are metal.

[Toobs]

Heres a dodgy diagram for you. (see attached)

[M.J.H]

If you know someone with a MS65 crown have a look at that.
Or have a look at any Falcon from the EA onwards as they all use the plastic one Toobs refers to.

[TurboRA28]

Thanks for the info all.

On ARE's website, they have overflow tanks. But these appear to use the pressuried cap.



If this is em.. The large pipe down the bottom, where would that go to?

That PDF file doesn't seem to be workign for me?

Thanks
Joel

[Hen]

I was of the opinion that most radiator header tanks were used to try and ensure all air was out of the cooling system. Especially useful if your radiator sits low (V mounted or boot mounted) as the radiator cap should be at the highest point in the cooling system so any air in the system ends up there.

The header tank basically just has a normal radiator pressure cap on it and does the same job a radiator cap usually does. Often they have multiple inputs from all locations in the cooling system which could develop an airlock, so any stray air bubble rise up to the header tank rather than staying there and becoming an airlock.

I have no experience with factory setups, this is just from what I have seen of "performance" setups.

Hen

[EDIT - in that above photo, I'd say the big feed is just a hose from rad/cooling system, the small feed is a hose from some airlock laden point in the system and the top little pipe is a normal rad overflow pipe]

[CrUZida]

Pretty sure Hen is right here.

The 1UZ Soarer's run them because the radiator cap is lower than the coolant passages in the motor.

There is no need for it if the radiator cap is the highest point in the system.

[YelloRolla]

Joel,
Ring ARE. I was walked through this exact scenario recently, and from what I recall what I am reading the above posts doesn't exactly fit....

[wagonist]

All the EJ20T powered Subarus ie WRXs, GT/B4/RS Turbo Liberties run an external header tank.

There's no rad cap on the rad at all.

I have yet to figure out why the turbo models have this, yet the non-turbo ones don't (apart from the turbo ones having an aluminium rad - irrelevant - & needing water feed/return from the turbo)

The main water feed for the engine bypasses this tank, but all of the auxiliaries (heater, turbo) run through it at some point.

[BeRad]

while were on the topic of overflows, ive got a stainless one lieing around its about 800ml that should be plenty big enough for a over flow correct?

[CrUZida]

Yeah, my factory one would be around the 1.0L mark.

[roadsailing]

Joel, i'll email you a design if i can both find it and scan it at work. hell overkill, but will work great.

otherwise just copy what fords use. (BA is a good place to start, but i think even the EBs had them) shouldnt be too hard. i'd like to make one for my car, cause its easier than fixing the leak in the radiator

EDIT:

also, for toobs' design to work, the lowest point of the tank must be higher than the highest point of the cooling system (head or whatever) if you are making a header tank, you might as well put air bleeds in too, to make filling easier. i'll dig out the design for you, PM me to remind me just in case.

EDIT 2:

the big pipe on the tanks you showed go to the bottom radiator hose, they do on the BA falcon at least.

[TheToyman75]

Damn what allot confusion

First - Ignore almost everything done on a Factory passenger car !! What you are seeing on most is a glorified overflow bottle, NOT a true Header tank set up as used for performance applications.

The Header tank concept is the same for all applications and serves one basic purpose, to alleviate air locks from the cooling system.

Basic points

# The header tank must be the highest point in the cooling system

# The small feed line/s to the Header tank must come from the pressure side of the cooling system, usually the thermostat housing (Pressure side) or the top of the radiator.

(Ideally you will run a line from the highest point in the head as well to bleed air from the engine) Both these lines are of the smaller size and feed to the Top of the header tank

# The considerably larger hose is the return form the header tank (Out the bottom) to the cooling cycle and must re-enter on the vacuum side of the cooling system. Usually to the vaccum side of the water pump or to the heater inlet pipe.


Hope that helps !

[wagonist]

Good advice from Rod there.

Thinking about it again, I've discovered why it was done in the turbo subarus & not the NA versions. Its becuase of the turbo position.
The water feed into the the top of the turbo is higher than the top of the rad, so to alleviate this, Subaru installed a header tank bolted to the intake manifold to make sure its higher.

I think the Falcon is the same because of the head being higher than the rad (I know it is in my BA)

The rad cap on both these cars is on the header tank.