Flushing Brake System with Denatured Alcohol

[Coastal220]

Originally Posted by Mike D

Not worth the time and trouble. Think about it. Anything which will eat paint from the exterior of your car (brake fluid) is probably strong enough to keep the system clean.

Do an annual flush as part of your spring "tune-up" routine and you'll be fine.

Sounds like firm logic, and for the most part I completely agree. Still, strange things happen in closed spaces that are seemingly self-supporting. Things tend to separate, congeal, turn to solids, react to their containers, the list goes on. I know brake fluid is designed to resist all of this, but for all I know the same fluid sat in the car for 15 or 20 years. Probably not, but who knows.

Moral of this story is I'm neurotic and always concerned with covering all my bases. So for this I apologize. Unless some crazy story comes in, I think I'm convinced that a brake fluid flush is enough.

[alabbasi]

ATE makes a DOT4 racing brake fluid that's blue in color which is great for flushing brakes.
Bleed the system until you get solid blue fluid out of the bleed nipples so that you know that you have all of the old fluid out.

[Palolo]

Originally Posted by sloride

Denatured alcohol is ethyl alcohol (ethanol) with an additive that makes it poisonous, while methanol is poisonous without any additives.

Exactly.

And the stuff you can buy OTC contains some water. The "purest of the pure" stuff is much harder to find if at all. (I grew up in a family of commercial distillers, and the stuff that came out the top of the columns was literally poisonous and burned with no visible flame)

I would also not use compressed air unless the line has a dryer in it. No point in forcing moisture laden air down a brake line.

[Coastal220]

Thanks guys,

I do plan to use ATE Blue. My compressed air line does have a separator on it, but I think I'll just see how the brake lines flush with clean fluid.

Also, I wasn't aware that denatured alcohol sold over the counter STILL has some water in it. I wonder how much... in any case, if I do any "cleaning" of the lines I'll use brake cleaner instead.

Cheers

[werminghausen]

Originally Posted by Frank Reiner

Coastal:

Re: Use of "Brake cleaner". Spray can brake cleaners are intended for use on metallic parts. They contain hydrocarbon based solvents which are not compatible with the rubber parts in the brake system. If you strip the system of all old rubber parts, and then flush the steel lines with cleaner, followed by air, there will be no hazard. The solvents evaporate quite quickly, so there should be no residual. When the system is reassembled and bled, it will be clean.

This is correct, flushing with brake cleaner makes only sense if no rubber is involved. So you need to disconnect the brake line from master cylinder and disconnect lines from calipers, then flush, then blow compressed air. Let it vent for some hours before you assemble.

[pop & blow]

what i do is put a catch bottle on each wheel and open up the bleeders and pour the new brake fluid in until all the old has been replaced. don't put alcohol is great for cleaning freshly hone wheel cylinders or cylinders honed in and engine block great for cleaning metal parts not so good on rubber parts like the cups in a wheel cylinder or master cylinder will cause problems, just put fresh DOT #3 and brake lines rust from the inside out, that is why you should flush every couple of years or just suck out the master and add fresh fluid.