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Coolant expansion tank empty

10K views 18 replies 8 participants last post by  M8TJT 
#1 ·
Hello,

I just checked my radiator level today and it is full to the top, but my coolant expansion tank seems empty. I can not tell for sure because it is so hard to check. Is that normal? I mean it is important for radiator to be full, I do not have any problems with heating. Temperature guide is always bellow half.

Honda fn2 type R


Thanks!
 
#3 ·
Of it was me, I would use Honda coolant and not just water.. as it mixes with your engine coolant, it will dilute it... the coolant has additives which prevent rusting, provide better cooling properties and also gives a lower freeze temp point for those winter months..
 
#15 ·
Yep, good old fashioned tap water!
Water boils and turns to steam at 100 degrees. Coolant doesn't = another reason not to use water. I had something similar with my mk8, radiator full yet expansion looked empty. i just bought a 1 litre bottle of honda coolant and topped it up until half way between low and full. It is difficult to reach and see what levels its at. I stuck my ledlenser on the side which lit up the interior giving me a good idea of its level.
 
#7 ·
Between min and max when warm from memory, I think it reads pretty low on a cold check.
I made the mistake of filling it cold and when my engine was hot the level was near full, had to buy myself a fluid syringe with a long tube on it and drained it until ok
 
#12 ·
He didn't say that he had got it, just that topping up with tap water can possibly cause it, however unlikely given the amount needed for a header tank top up.

What really surprises me is that the OP needed to ask about topping up the coolant in the first place.
 
#19 ·
At an absolute pressure of 30 psi water boils at 121C REF
As atmospheric pressure = about 15psi add 15 psi = 30 psia = 121C so I wasn't far out.
And I did say "about" as I can't be assed to do it to the nearest 0.1C

The point that I was trying, but obviously failed, to make was that the coolant in a car is much more affected by the pressure in the system than the actual coolant mix.
 
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