Header tank

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paulsv8manta
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Header tank

Post by paulsv8manta » Thu Apr 12, 2018 10:24 pm

Hi guys, a simple question this time.
Do I need to install a header tank or can I run my 3.5 without one?



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Re: Header tank

Post by SuperV8 » Fri Apr 13, 2018 9:25 am

As your coolant expands you need somewhere for this to go!

There are two options and the names often get confused or interchanged - by me also..

It depends on your coolant/rad cap.

If its sealed (up-to the pressure relief value; often 15psi) with one seal and no overflow outlet then you need an header tank - Just a tank at the highest point in the system with one outlet at the bottom - which tees into your bottom hose, an with an amount of air for the coolant to expand into, and a small vent inlet above the coolant level with a small pipes coming form any high points where air might collect.

If your cap has two seals and an overflow then you need an expansion tank/catch tank - this tank can be anywhere but normally next to the rad and the cap needs to be the highest point of the coolant system. This cap also has an additional expansion relief seal which opens at a preset pressure (lower pressure), the expelled coolant is collected by the catch tank where the hose goes in the bottom of the tank - below coolant level. When the system cools it will suck in the coolant back into the rad. This catch tank is not sealed.

Tom.
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Re: Header tank

Post by DaveEFI » Fri Apr 13, 2018 11:52 am

paulsv8manta wrote:
Thu Apr 12, 2018 10:24 pm
Hi guys, a simple question this time.
Do I need to install a header tank or can I run my 3.5 without one?
Depends on the rad you're intending using. Has it a big enough header/expansion area built in? Using a separate tank allows a smaller/lower overall rad size.
Dave
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paulsv8manta
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Re: Header tank

Post by paulsv8manta » Mon Apr 16, 2018 7:33 pm

hi guys thanks for replying, and sorry it's taken me so long to come back, i've got another problem with the dam engine now!
Anyway the radiator i'm using is from a skyline R32 all aluminium. The rad cap was rated at 1.1 bar and has two seals and an overflow.
I've just changed the cap for a 1.3 bar hoping this would do the trick, but it looks like I need an expansion tank/catch tank.

Hi Tom, you say - this tank can be anywhere but cap needs to be the highest point of the coolant system.
That's going to be a problem for me as the heater matrix by the bulkhead is the highest point which is why I've i've installed a bleed valve.

This cap also has an additional expansion relief seal which opens at a preset pressure (lower pressure), ---- (I take it this is the catch tank your talking about?)

the expelled coolant is collected by the catch tank where the hose goes in the bottom of the tank - below coolant level. (Now i'm lost)
When the system cools it will suck in the coolant back into the rad. This catch tank is not sealed. (Now I'm totally lost!)

The catch tanks I've seen have one inlet at the bottom of the tank and a screw cap lid with an O ring.

Any chance you could elaborate this for me in layman's terms.

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Re: Header tank

Post by unstable load » Wed Apr 18, 2018 1:00 am

A few Rover P6 guys have used the Mini header tank in their cars. The pressure cap stays on the rad and the tank is there for containing expansion overflow.
Cheers,
John

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Re: Header tank

Post by r2d2hp » Wed Apr 18, 2018 7:19 am

I don't think you might have a header tank and not a catch tank.

The catch tank does not have a pressure cap.
This is an example from a Honda S2000. the overflow from the rad feeds to the catch tank cap. It has an internal pipe that extends to just above the bottom of the tank.

https://www.s2ki.com/forums/attachments ... image.jpeg

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Re: Header tank

Post by SuperV8 » Wed Apr 18, 2018 11:43 am

Anyway the radiator i'm using is from a skyline R32 all aluminium. The rad cap was rated at 1.1 bar and has two seals and an overflow.
I've just changed the cap for a 1.3 bar hoping this would do the trick, but it looks like I need an expansion tank/catch tank.
With the Nissan rad with two seals in the cap; the cap would need to be the highest point in the system, if the heater matrix is the high point then any air would collect there.
With this Nissan radiator the hose from the cap should go into the overflow/catch/recovery tank. As the engine/ system heats up and coolant expands, coolant is expelled passed the first seal at 1.1 bar through that small hose into the overflow/catch/recovery tank. That hose would need to go to the bottom of the tank, either externally or internally is fine but the outlet needs to be submerged under coolant so it can't suck air. This tank also needs to be vented to atmosphere (i.e. not sealed as that could over pressurize the system) As the engine cools it will create a slight vacuum in the cooling system which will draw back coolant from the recovery tank through the hose and through a one way valve in the centre of your rad cap.
Hi Tom, you say - this tank can be anywhere but cap needs to be the highest point of the coolant system.
That's going to be a problem for me as the heater matrix by the bulkhead is the highest point which is why I've i've installed a bleed valve.
This cap also has an additional expansion relief seal which opens at a preset pressure (lower pressure), ---- (I take it this is the catch tank your talking about?)
As your rad cap isn't the highest point in the system I think you will need to use a header tank type system, the 1.3 bar should be fine for your rad cap. Tee into the bottom radiator hose with a hose connected upto the bottom of the header tank. The coolant level in this tank now needs to be the highest point in your system, i.e. higher than your heater matrix. Don't fill the tank as the air volume will be where the coolant expands to as it warms.

Tom.
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Re: Header tank

Post by SuperV8 » Wed Apr 18, 2018 11:49 am

Dax Rush 4.6 supercharged V8 MSII

paulsv8manta
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Re: Header tank

Post by paulsv8manta » Thu Apr 19, 2018 9:42 am

Hi guy's, many thanks for all your help, and Tom that link - fantastic, especially leading to http://www.pirate4x4.com/tech/billavist ... stemBasics

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