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Discussion Starter · #1 ·
My 4.6 V8 Moggy has no header tank or expansion tank. If you fill the top hose to the top, it spews out about 3/4 of a litre onto the road as soon as it gets hot!


As I understand it, I have 2 options. Firist I could fit an expansion tank onto the overflow on the exisiting filler (Red circle), so it can push out a load of coolant when hot and suck it back up again when cold (I have the right cap already). This is an easy fix as it can be put more or less anywhere and I could use more or less anything such a JD bottle etc, as its not pressurised.

I think the better option is a header tank which is pressurised and has to situated at the highest point on the cooling system. Most tanks seem to have an outlet that goes to the lower rad feed, an inlet that goes to the top rad bleed pipe (Green circle) and an overflow which can vent to the road. I have found a fairly cheap ali tank that just has an outlet and overflow which could just be plumbed into the top rad bleed for a simpler install.

This is the cheaper option:

And this is the more (4X) expensive option:

Any suggestions on what's best, what looks good and works, safely?

Premium Member
14,514 Posts
You are not meant to fill a std system to the top, so it will always spew out your amount - it's just finding it's correct level. Water expands when hot - so it's got to go somewhere.
Does it overheat? if not then leave it alone.
agreed, let it chuck out the excess and watch the gauge. if it doesn't get hot and doesn't throw any more out it's fine. it's obviously not a fresh build with teething problems so as mark says just don't fill to the top.
my dad had some lorry drivers that complained they were always topping up coolant, start of day and before returning to base. they were filling to the top when the header tanks were clearly marked max about 4" down, the numpties.
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