taylorslandy72

taylorslandy72

Active Member
Hi all, been out trying to bleed all the brakes on the s3 and couldn't stop getting air through, found out I was using some old fluid, is this what happens when it's gone off?
 
no.

it's hygroscopic so absorbs water which can rust internals and lower the boiling point, so your brakes boil when heavy braking; which is why you are meant to change it every x years
 
trax said:
no.

it's hygroscopic so absorbs water which can rust internals and lower the boiling point, so your brakes boil when heavy braking; which is why you are meant to change it every x years
Click to expand...

I didn't think the new synthetic fluid was hyoroscopic?
 
smnbyt said:
I didn't think the new synthetic fluid was hyoroscopic?
Click to expand...

Silicone fluid (dot5) is not hydroscopic but dot4 is. The dot 5 can get water droplets that will can cause corrosion and if you worry about the reduction of boiling point of normal fluid, then water will be much lower.
 
don't stick dot5 in. it doesn't mix with 3,4,5.1 and will cock things up.

you'd need to do a proper purge if you want to use it... and like there's not too much point really
 
the tins might be alright you know.. plastic i dunno, i'd use unopened plastic if it was a few years old.

but it's cheap enough to not risk it :D
 
trax said:
no.

it's hygroscopic so absorbs water which can rust internals and lower the boiling point, so your brakes boil when heavy braking; which is why you are meant to change it every x years
Click to expand...

And the water helps to corrode everything from the inside out
 
Last edited:
SpringDon said:
Oh, I see. That's not confusing at all.
Click to expand...

Tell me about it! DOT stands for Dept of Transport, USA - which explains _everything_... <grin>

It does make a bit more sense than it first seems. DOT3 was the "main" standard, which was improved for DOT4, with higher boiling points, as technology improved. Then DOT5 was introduced, still higher, and it wasn't hygroscopic (moisture-absorbing!) GREAT! Except... it was found to be really difficult to bleed, and wasn't miscible. So a revised standard - 5.1 - was introduced. Same higher boiling point, without the drawbacks, but still hygroscopic. And that's where we are today.
 
Last edited:
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