Thread: Brake Fluid

Originally Posted by discoute

I have in the past when helping a friend at his house used a damp sponge stuffed in the top to get most of the fluid out. Brake fluid is water based.

Just go easy when you bleed it should be ok.

glen

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Never heard that brake fluid was water based - this is the NORMAL comp of DOT 4 Brake fluid.

MIXED ALKYL ESTER 35.0- 45.0
TRIETHYLENE GLYCOL MONOBUTYL ETHER 143-22-6 20.0- 30.0
TETRAETHYLENE GLYCOL MONOMETHYL ETHER 23783-42-8 5.0- 15.0
POLYETHYLENE GLYCOL 25322-68-3 5.0- 15.0
TRIETHYLENE GLYCOL MONOMETHYL ETHER 112-35-6 5.0- 15.0

Water destroys the boiling point of brake fluid!
See this link.

http://www.xs11.com/tips/maintenance/maint1.shtml

Trev.

Originally Posted by ladas

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Never heard that brake fluid was water based - this is the NORMAL comp of DOT 4 Brake fluid.

MIXED ALKYL ESTER 35.0- 45.0
TRIETHYLENE GLYCOL MONOBUTYL ETHER 143-22-6 20.0- 30.0
TETRAETHYLENE GLYCOL MONOMETHYL ETHER 23783-42-8 5.0- 15.0
POLYETHYLENE GLYCOL 25322-68-3 5.0- 15.0
TRIETHYLENE GLYCOL MONOMETHYL ETHER 112-35-6 5.0- 15.0

this makes it highly hygroscopic (absorbs water)

Check out the wet, as well as dry boiling point if you are checking out a premium fluid.

Castrol's deservedly famous SRF racing brake fluid has probably the best wet boiling point I can recall as it uses a Silicone Ester base vs polyglycol of normal fluids (not to be confused with Silicone brake fluids, which are compressable and therefore give a spongy pedal when hot) and I think the best/least compressability of any commonly available fluid.
Unfortunately it's price reflects its ability. No way I'd run it in a road car unless I was doing track days.

I tend to use Castrol Response Super DOT 4, the stuff developed for Porsche and BMW ABS systems

Dawg, don't know if I can lay claim to its invention. Honestly can't remember, it was years ago, but generally I'm much better at nicking someone elses idea and modifying it than coming up with something original.

" I tend to use Castrol Response Super DOT 4".

So do I. It's cheap and available everywhere. Why buy the normal Castrol Response for $6 odd, when the Castrol Response Super DOT 4 is only $8 odd (for 500ml bottles).

Being hygroscopic, is the reason the brake fluid must be flushed/replaced every 2 years and why you should never top up your brake fluid with a previously opened bottle.

My brakes failed about 2 years ago when I was going to a camp site in Oxley Wild Rivers National Park and the drive down is quite steep. I was in low range, but it wasn't ridiculously steep so I would accelerate in between erosion mounds, then brake. This got the brakes hot enough to boil my old fluid and made the brakes fail. Wasn't a nice feeling having the pedal go flat to the floor when I needed them (by luck, this happened at the bottom of the hill!). And no, I don't think I over used the brakes to the point where they should fail - people tow tonnes with these cars.

When I got home (brake were fine when cold again) I replaced the fluid and the old fluid was brown and dirty. I'm also willing to bet that moisture in the fluid can cause parts of the braking system to corrode??? But I'm no expert.

Correct on all accounts, for anyone that anally retentive I can see if work will let me have a copy of the brakes + brake fluid safety and precations vid they make us watch before doing any brakes module.

Its got a section of tab data on the effects of using contaminated brake fluid. admittedly its old but I was amazed to find out that leaving brake fluid open to air for 5 days essentially renders it useless.

Originally Posted by rick130

this makes it highly hygroscopic (absorbs water)

Check out the wet, as well as dry boiling point if you are checking out a premium fluid.

Castrol's deservedly famous SRF racing brake fluid has probably the best wet boiling point I can recall as it uses a Silicone Ester base vs polyglycol of normal fluids (not to be confused with Silicone brake fluids, which are compressable and therefore give a spongy pedal when hot) and I think the best/least compressability of any commonly available fluid.
Unfortunately it's price reflects its ability. No way I'd run it in a road car unless I was doing track days.

I tend to use Castrol Response Super DOT 4, the stuff developed for Porsche and BMW ABS systems

I am working on a PAO (Poly Alpha Olyfin) based brake fluid - a run off from our standard PAO based refigerant lubricants- the up side if I can get it to work / correct density and viscosity - is PAO's are virtually non hygroscopic

.....................but I think I have a bit of work to do yet, so don't hold your breath.

aaah, Mr Roc oil !

how do you get a PAO to work in a refrigeration system without using an ester for additive solubilty and to offset the seal neutral/slight shrinkage of a PAO

Used your stuff for years now, although still not sure how you've made it work with such a high PAO %

watch out, there's a few Fridgies on here.....