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Discussion Starter #1
This time for those who have vacuum changed the coolant using a hand pump ( fluid/oil extractor) Does it matter what capacity the extractor pump is ?
I was loaned a 2.75 litre capacity oil extractor but can't seem to get enough pressure build up to draw enough coolant into the system ?
 

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As long as you can draw a vacuum with the pump, it should work. I built a system using my hand vacuum pump from my brake bleeder and it worked fine. It will be critical to ensure a good seal with whatever your using so the vacuum can actually build in the system before you open up the valve to allow the coolant to be drawn in.
 

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Discussion Starter #4
Thanks guys.
I built a system almost identical to the one on this old thread on here.
http://www.k-bikes.com/forums/showthread.php?p=155070#post155070
One thing that crossed my mind was whether I might be getting a vacuum leak ?
I did use compression fittings with ptfe sealant tape ?
But today I ensured everything was tight and could still only manage to get the vacuum gauge to pump to 0.4 , it does draw in fluid, but the vacuum soon drops and nowhere enough coolant is drawn into the system.
Should i go ahead and order a bigger fluid extractor ( 6.5 litre ) ?
 

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I bought a vacuum to change my fluid. Even with that, i had a small leak and couldn't get vacuum. Even with clamps on the hoses, I had a leak. It wasn't until I FOLDED OVER the hose on the bottom of the bike AND clamped it that I got vacuum.
worked perfectly and fast.
 

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It's also important to make sure that the coolant supply is higher than the top most point of the cooling system. The purpose of drawing the vacuum on the system is to enable you to start a siphon effect from the supply into the cooling system. Once that is established, the siphon is what feeds the coolant in and fills the system to full and the vacuum is no longer needed. Having no leaks in the filling system is still important to ensure the siphon is maintained and the coolant completely fills the cooling system leaving no air pockets.
 

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Discussion Starter #7
The coolant container is higher than the rad so shouldn't be a problem there.
I'm going to use some gasket sealer on the threads today, but reading the rep rom it would appear that a minimum of -0.8 bar should be achieved , I can only get my gauge to go to 0.4
With the small oil extractor pump.
It starts to draw in fluid ,but after a short time it just stops dead, probably after drawing in just 0.5 litres of coolant ?
Nowhere near enough , so it's either the pump hasn't a big enough capacity or there is a vacuum leak ( when pumping at the 0.2 mark a load whistle type noise is heard but then dissapears ?)
I have a 6.5 litre pump coming today ( this service is rapidly costing more than it would have at BMW ! Lol ! ) but will try the gasket sealer and the small pump again first and try that tip of folding over the bottom hose.
 

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Once the coolant flow is established and the vacuum you had is depleted, you need to open the bleeder valve on the top of the engine to allow the coolant to continue flowing. If you were able to get the coolant flow started with the vacuum, it should keep going. Like I stated before, the siphon is what really does the job of filling the system up, but you do need to open that bleeder to allow that to happen.
 

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Discussion Starter #9
Thanks guys for your input.
Using the larger pump I got it past -0.8 quite easily.
All done and dusted.
 
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