Question Coolant backing up into fill tube

adsoyo

Distinguished
Mar 26, 2012
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I've been running this custom loop for a little over a year now and it's been working great. No leaks, low temps, nearly silent. I noticed the coolant in the res looked like it lowered, not uncommon as air bubbles work their way out of the nooks and crannies. I went to add a little but when I unscrewed the fill port, the coolant was backed up all the way to the top. Has my loop built up pressure due to the heat cycling? Would my loop benefit from a pressure relief valve on the res? I don't want it to start bursting at the seams.

 

Eximo

Titan
Ambassador
Outside air pressure changes, air pressure inside changes with temperature, ambient temperature changes. Yes, if it well sealed there will always be a pressure differential between it and the environment.

As long as the fluid is moving and the tubes aren't collapsing, not much concern. The fluid is non-compressible so makes no difference to the pump.
 

rubix_1011

Contributing Writer
Moderator
Looks like the fill tube in the top of your reservoir has the dip tube in place in the interior of the top cap?



This would be one reason why it is rising - when barometric pressure changes on the soft tubing of the cooling loop, it will 'squeeze' the coolant up into this tube because it is below the siphon line (coolant level in the reservoir).

Basically, if you squeeze any tubing with your fingers, you should see this rise and fall as you apply pressure/let go.

There isn't a problem here, but if you don't want this to occur, you'd want to remove the siphon tube from the reservoir top cap on the inside, then put back together as usual.
 

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