Difference between header tank and expansion tank?

Obonobo

Hello all!

I am about to work on my (what is supposed to become very) cool plumbing, but I am confused about the different types of tanks used in the various builds on this forum.

My question:
What is the difference between header tank and expansion tank?

Here is my understanding: a header tank should be the highest point in the cooling system. Then all air in the system will rise here and be discarded. According to the schematic of RJES it is connected to the water manifold (from pip on manifold to large pip on a, say, T25 header tank) and to the heater matrix (small pip on header tank). The header tank needs an overflow tank, so any excess coolant is not sprayed around the engine bay.

On the RJES schematic there is no mention of an expansion tank. Why is this not so? And in what kind of schematic should it be?

I browsed around on the forum, but I actually became more confused because of the many different schematics I found.

BTW, my project is building a EJ22 in a '75 bay, rad between the rails, using a reversed manifold and wanting to put on or two heater matrices in the cooling circuit.

Thanks for any help!
_________________
Greetings from Sietze
-------
Driving a '75 Bay with a EJ22 '93 and 091 6-rib box.

And it's a long time since it looked anything like this!

P4UL · Padawan Joined: 13 Sep 2010 Posts: 83 Location: Derbyshire

Your right in what your thinking about the two tanks.

On RJES's circuit diagram the expansion/overflow tank is item 17.

ElusiveStranger

Obonobo · Posted: Mon Jun 27, 2011 10:11 pm Post subject:

Thanks guys: clear answers, clear mind!

Best/safest option for durable non-bubbliness seems to be the Frontera-type tank.

Great! And now: to the scrapper!
_________________
Greetings from Sietze
-------
Driving a '75 Bay with a EJ22 '93 and 091 6-rib box.

And it's a long time since it looked anything like this!

ElusiveStranger · Posted: Mon Jun 27, 2011 10:37 pm Post subject:

You can use a T3 in the same way, here's Kev's:

_________________
The advice you receive on here is worth the paper it's written on.
Your experiences are worth shed loads to others, including the f'ups - live and learn.
Wouldn't YOU rather learn by someone else's mistakes? So would they.

'78 Bay, 2 litre 091 box, EJ20 NA & the ashtray's on the 'right' side.
I don't lean forward for hills any more Grin

Bugger, missed out on "Live fast, die young"

Obonobo · Posted: Thu Jul 07, 2011 7:48 am Post subject:

Thanks, that's clear!
_________________
Greetings from Sietze
-------
Driving a '75 Bay with a EJ22 '93 and 091 6-rib box.

And it's a long time since it looked anything like this!