I'm trying to understand the coolant Reserve tank

lloydie · Post by **lloydie** » Fri Dec 27, 2013 7:24 pm

I've been thinking about removing or relocating the coolant Reserve tank to aid access to mixture adjustment screws but I'm struggling to find a reason why the bottle needs to have coolant in it .

In the service manual it says " Fill the reserve tank to the upper level line with the motorcycle upright on a flat. level surface"
now when I stripped the bike down I noticed the reserve tank had only two pipes
One from the filler neck on the right hand radiator going to the bottom of the reserve tank and the other one from the top of the reserve tank going out to the floor as an over flow .
Now with only one pipe coming from the radiator as a overflow how can it use the coolant in the reserve tank as it has no way of returning as the bottle doesn't have a pump to put it back in the system .
I can't see it being sucked back in as the cooling system has a positive pressure and even if the filler cap opened to let it in there will be 16-20 psi stopping it returning .

Earlier this year I filled the cooling system with pink coolant and filled the reserve tank with green coolant .
So when I stripped it down I was expecting them to be mixed together but they were not ! .
So another question . Is the reserve tank really needed ?

Jamoi · Post by **Jamoi** » Fri Dec 27, 2013 7:31 pm

Good question, I was wondering what the point of it was when I was putting it all back together, what with being a plumber and all.

I don't know the definitive answer but I'd like to know also.

darkember · Post by **darkember** » Fri Dec 27, 2013 8:31 pm

As far as I now as the temperature rises in the radiators the pressure will increase within the system & needs to expand somewhere hence the expansion tank. If you want to remove the expansion tank then I would move over to that fancy coolant that does not create pressure within the system.

AMCQ46 · Post by **AMCQ46** » Fri Dec 27, 2013 8:34 pm

as far as I can work out it is only a catch tank for expansion if it boils, I can't see how it can go back up into the rad either

Jamoi · Post by **Jamoi** » Fri Dec 27, 2013 8:42 pm

Can't understand why there is a need to fill it up with coolant, if the expansion vessel can only 'receive' coolant...? Odd!

lloydie · Post by **lloydie** » Fri Dec 27, 2013 8:46 pm

Jamoi wrote:Can't understand why there is a need to fill it up with coolant, if the expansion vessel can only 'receive' coolant...? Odd!

thats whats doing my head in

lloydie · Post by **lloydie** » Fri Dec 27, 2013 8:50 pm

darkember wrote:As far as I now as the temperature rises in the radiators the pressure will increase within the system & needs to expand somewhere hence the expansion tank. If you want to remove the expansion tank then I would move over to that fancy coolant that does not create pressure within the system.

but once its left the system through expansion it cant go back it . so i would think having an empty reserve tank would be better to keep an eye on as if it had coolant in it you know the radiator needs topped up .

Gazfirestormowner · Post by **Gazfirestormowner** » Fri Dec 27, 2013 9:34 pm

As far as I know as the coolant in the radiator cools it creates a vacuum that sucks the coolant back into the radiator

lloydie · Post by **lloydie** » Fri Dec 27, 2013 9:42 pm

Gazfirestormowner wrote:As far as I know as the coolant in the radiator cools it creates a vacuum that sucks the coolant back into the radiator

But the rad cap only opens at 16-20psi so liquid can exit and a cooling down system will be a lot lower than that so it can't suck it back up as the cap will be closed anyway .

mattycoops43 · Post by **mattycoops43** » Fri Dec 27, 2013 9:44 pm

+1

What he said.

Rads expand, push out a small amount, when cools sucks back in. only a small amount though. fluid in th tank stops rad sucking in air.

Thats the theory anyway.

:beer:

darkember · Post by **darkember** » Fri Dec 27, 2013 11:28 pm

Capillary action & +/- pressures. Lloydie fluid will move back & forth otherwise the expansion tank would overflow over time. Another more extreme example would be to pour boiling water into an empty pop bottle & screw the lid back on then watch it implode as it cools

macdee · Post by **macdee** » Sat Dec 28, 2013 1:20 am

loydie I have had a good ponder over the expansion bottle question and have come to the conclusion that its inclusion on the bike is more for safety an a visual reference point
safety in that it collects boiling water( if their is a problem )and dispossess of it by mixing it with cold coolant and then on to the ground
visual as it gives the user a chance to see that he or she has an over heating problem by the fact that there is more coolant in the bottle than their was before the journey ,the colour of the coolant helping to verifier the level better than water which is clear
the fact that the bottle is mounted lower than the filler cap and has only a snap lid means that it cant be use in the traditional manner which would require it to be mounted higher than the rads with the expansion cap on the bottle and a return pipe to the cooling system as in most cars etc
also worth pointing out that antifreeze is toxic maybe the bottle is there to meet some regs
this is in my professional opinion as a fully qualified EEJIT
PS I would like to here from Roger as to what system he ran on the race bikes

bigtwinthing · Post by **bigtwinthing** » Sat Dec 28, 2013 7:31 am

its there so that as the coolant heats up and expands you don't get coolant running all over the bike, its very toxic and bloody poisonous so don't swallow any.As the system cools it stops air being sucked into the system. Not sure how it gets back in but air in the system will make things run really hot. ( its a major problem in my job where our cooling systems use 500lts of coolant and we need to bleed off with every head change)

Tweety · Post by **Tweety** » Sat Dec 28, 2013 8:21 am

Well, high or low pressure aside, it does actually work like described above... The coolant that has been pushed out when hot returns back into the engine when it cools, by back pressure... It is needed, but it doesn't need to be as big as it is, and it doesn't need to be placed there...

MacV2 · Post by **MacV2** » Sat Dec 28, 2013 2:01 pm

http://www.ebay.co.uk/itm/New-HRC-Honda ... 256abbca1d

Smaller & HRC kudos !

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