Subaru coolant system

graham-e · Posted: Wed Jan 12, 2011 9:41 pm Post subject: Subaru coolant system

I'm rethinking my coolant system...
Because after running the engine for about 10 minutes to let it warm up, coolants started spraying out the pressure cap on my header tank.
My header tank is from a porsche and has the overflow built in, i plumbed this into the heater hose near the thermastat. Should this work or have I made a mistake? I bleed the air from the top hose by loosening it off so there isn't any air in the system.

Does this diagram look right to you?

I'm thinking of removing the header tank and putting one of these in the top hose, with the outlet attached to an overflow tank..

Recon this will work? I thought I knew how coolant systems worked.. until now

ElusiveStranger · Posted: Wed Jan 12, 2011 11:53 pm Post subject:

Where's your rad? If it's below the engine ie chassis rail job, following the Subaru system won't work! Well not very well as you've found out & so did I 5years ago.

Plenty of pictures and drawings of schematics on here :-)
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'78 Bay, 2 litre 091 box, EJ20 NA & the ashtray's on the 'right' side.
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Bugger, missed out on "Live fast, die young"

graham-e · Posted: Thu Jan 13, 2011 12:07 am Post subject:

yeh, i've got a couple if ford radiators in between the rails..

I've confused myself i think, because i thought you had a conventional pressure cap, which if the pressure rose too much it opened to relieve it, and upon cooling down that expelled fluid was drawn back in. But how do systems with screw on caps relieve excess pressure?

ElusiveStranger · Posted: Thu Jan 13, 2011 12:49 am Post subject:

Okey dokey, I'm now on the puter not the phone.

Here's the theory (pull up a chair, I'm hopefully typing in a jovial manner):

Subaru system
Rad's "in" is higher than the block. Air/vapour naturally wants to rise from the block (when engine's NOT running), so it bubbles into the rad. Fire her up and the small tubes on the block (IAC, TB) flow water to the 'stat and matrix. Simples Happy

Now when this system heats up, the air (now in the rad) expands, remember it wants to be at the top? So it buggers off down the "expansion tube" on the Subaru cap, along with some water. When the system starts to cool it creates a vacuum (nature abhors this) and it sucks up the water from the expansion tank (the air's buggered off into the ether by now)

On a underfloor setup
(ummm under engine rad) where's that air/vapour going to go?
Well alot of it's gonna run into your matrix line (you'll hear it bubble round the matrix if it's up front) , shortly followed by into the waterpump. Now hazard a guess why it's called a water pump - it won't pump air, not that it'd do any good if it did.
Right, one place where air/vapour also likes to sit is where I call "A high spot in a low place". Imagine a toilet U bend but upside down. Pound to a penny you've got one and it's the big return pipe from the rad to the stat. That one that goes over your torsion tube then down at the engine. Don't panic though, I'll tell ya later.

Right a "flow through" header (like mine) goes between the engine and the matrix line. All that vapour (cold engine) gets forced into the top pipe of the header tank (mine's a Frontera, T3 tanks work well too) and only water comes out of the bottom.
So we now have a happy(ish) engine.
A proper flow through would take all the engine hot water through it and split some to the matrix, rad etc

Up there ^^^^ I was burbling on about toilets and U bends, yeah? Well that pipe is a PITA to start with on bleeds (I did have a bleed system on it ages ago, scrapped that). Fire her up and bleed as much as you can (statically). When it's up to the 'stats open temp...Pull away with a bit of gusto. Pull over, stop, and do it again (Rinse and repeat as necessary as they say on shampoo bottles). Once it's bled it's fine Happy

With the Frontera tank you run it approx 1/3 full of water as it acts as a combined header & expansion tank (like a pressurised central heating system). If you use a T3 (or similar) use it as you normally would ie fill to the max mark and connect the expansion tank up

Hope that clarifies it.

Post up a picture of your header tank and engine bay and we'll have a think Happy

_________________
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"

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

Very useful reply ES, learnt about header tanks, something Ive been pondering on. Thanks.

ping · Posted: Thu Jan 13, 2011 5:58 pm Post subject:

Which type of frontera tank did you use and can you elaborate on where you connected each outlet to in relation to the scooby engine? I'm confused about headder connecting.

ElusiveStranger · Posted: Thu Jan 13, 2011 7:04 pm Post subject:

ping · Posted: Thu Jan 13, 2011 7:56 pm Post subject:

Thanks for that, i've got a golf mk3 header tank i was going to use but i'm struggling as to where to T in to the system. I have one 16mm pipe at the bottom of it and one 8mm pipe at the top, so one outlet less than the frontera header! I have aslo looped my heater system for now as i wasn't going to install a heater.
What i think i may do looking at your design is to T in to the looped heater pipe for the 16mm bottom pipe and then T in to the top hose on the manifold for the 8mm top pipe. Any thoughts on this?

ElusiveStranger · Posted: Thu Jan 13, 2011 8:00 pm Post subject:

You don't need the pink line... but run one to the engine bay (or somewhere) & bung a bung in it. I'll help you to initially bleed the rad
_________________
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"

ping · Posted: Thu Jan 13, 2011 8:06 pm Post subject:

Good idea with the bleed line. I think i'll do that as well.

ydeardorff · Initiate Jedi Joined: 02 Jan 2011 Posts: 32

I too am looking at doing something like this with my sterling.
heres the link:
http://www.lamborghinigallardopic.com/lamborghini-gallardo-lp550-2-valentino-balboni-race-car

The black and white picture there shows a similar layout to what I have planned. Any help or thoughts on how to make this system self bleed air from the system?
The engine will be higher than the rad like in the photo.
(WRX 2.0 turbo engine, with lines plumbed in the shifter tunnel, or along the side heater channels)
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Sterling Kit car (VW based) Project

Current donor car and engine:
2005 WRX Turbo

Looking for 200 to 250HP lump, Found it = WRX

ElusiveStranger · Posted: Sat Jan 15, 2011 2:07 am Post subject:

Do us a quick sketch of what you think will work. A few side photos of the car would help.
Have a gander at the Lotus Elise/Exiege(SP?)/VX220
_________________
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"