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do I actually need a header tank?
rumplitter - 19/1/09 at 12:56 PM

I have a mid engine honda B18c4.

My question is: do I actually need a header tank? Can I not just install an in-line filler neck on the highest point on the top hose?

The original system will have just had a filler neck in the rad. With an overflow outlet sust below the neck, running to a reservoir( I presume an expansion tank). The in-line filler neck I've seen has a 8mm overflow outlet, if I connect this to a reservoir surely this is no worse than the original set up?

mad4x4 - 19/1/09 at 01:03 PM

My zetec doen't have a header tank, I do have a small expansion bottle of of the rad overflow but thats it.

My Rad has a filler cap on it.

Never had problems with boiling

Mr Whippy - 19/1/09 at 01:22 PM

At some point in the system you will require a pressure valve to raise the boiling point of the water. Ether that can be on the radiator with a bottle (expansion tank) after at , which is open to the atmosphere, excess coolant is bleed out into the bottle or the whole expansion tank itself is under pressure and it has a pressure cap on it instead of the radiator.

I the case of the radiator mounted pressure cap, when the coolant cools down and its volume shrinks the cap is designed to suck from the bottle to make up the coolant volume again. This means the bottle can be much lower than the engine.

The same thing happens with the Pressurised expansion tank but it drains back mostly under gravity, so the bottle is usually mounted higher than the engines cylinder head.

rumplitter - 19/1/09 at 01:54 PM

Thanks Mr Whippy,

I've seen an inline radiator filler neck in car builders solutions catalogue. I was thinking of fitting this at a high point on the top hose between the rad and the engine. (closer to the engine, mid engine car) this would have a radiator cap with an 8mm overflow outlet directly below. Which i prsume i could fit a an expansion tank to. Like you say as the pressure builds up water would be forced out into the expansion tank then sucked back in as the water cools.

Does that sound right?

If so, no need for a header tank?

contaminated - 19/1/09 at 02:15 PM

Yes that would be fine. The little bottle or whatever (I use an anodised drinks bottle) needs to be vented (just nit sealed air tight) and with enough coolant in it to cover the end of the 8mm tubing.

rumplitter - 19/1/09 at 03:18 PM

so what is the beafit of fitting a header tank?
I don't see the point?

coozer - 19/1/09 at 03:45 PM

quote:
Originally posted by rumplitter
so what is the beafit of fitting a header tank?
I don't see the point?


OEMS put them in cars so why don't we? There is obviuosly a benefit being that with a n expansion tank your not chucking coolant out and not having to keep topping the system up.

rumplitter - 19/1/09 at 04:24 PM

why would you have to top the system up?

what's the obvious benefit?