ATF IN BRAKE MASTER CYLINDER?

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Don't! Brake parts are made from rubber that will absorb hydrocarbons and swell. If you must add something to limp home, go with the body fluids, undrunk beer, antifreeze, but not power steering, AFT, oil, gas, etc. Body fluids will lower the boiling point, and cause corrosion. However, after a complete flushing, the brake system should still work except for what ever caused the original loss of fluid. They are still using modern versions of what was available when hydraulic brakes were first available. Brake fluid is a water soluble poly glycol. AFT is parafffins or esters the same as motor oil, just lighter ones, or a leas without the VII.

We made a lot of progress in formulating rubber between the development of hydraulic brakes and automatic transmissions and power steering. There are even industrial brake systems that do use the hydrocarbons. I see no reason brakes couldn't switch, but the polyglycols are the way it has always been, and we mustn't confuse people by changing.

Best thing is to rebuild calipers and wheel cylinders every lining change or so and never have an emergency. Hoses eventually go, and in the rust belt, the steel lines too.
 
I wouldn't recommend any substitutions for brake fluid, but alcohol would be much better than water.

Hydrocarbons are a no-no for the reasons Labman gave.

Another reason is that hydrocarbons aren't miscible with with brake fluid (won't mix with brake fluid) so the resultant mess would be lot harder to flush out of the system.

Alcohol would greatly lower the boiling point of good brake fluid.
 
quote:

Originally posted by TomH:


To answer your other question, brake fluid (DOT 3 and 4) is a "glycol" based fluid, ATF is a "petroleum" based fluid. They have two totally different chemical makeups and are not compatible with one another.


Is the glycol in BF at all close to that in coolant?
 
quote:

Originally posted by XS650:
I wouldn't recommend any substitutions for brake fluid, but alcohol would be much better than water.
...

Alcohol would greatly lower the boiling point of good brake fluid.


Would that be isopropyl or the kind you can drink? Or does that matter?
 
I had an old Haynes manual that recommended flushing brake systems with Wood Alcohol (Methanol). So I guess that would be your best bet.

It always seemed silly to flush with anything else but more brake fluid.
 
quote:

Originally posted by JAYCEE:

quote:

Originally posted by XS650:
I wouldn't recommend any substitutions for brake fluid, but alcohol would be much better than water.
...

Alcohol would greatly lower the boiling point of good brake fluid.


Would that be isopropyl or the kind you can drink? Or does that matter?


Not much, but it's usually easier to find brake fluid than close to pure alcohol. Whatever is used instead of brake fluid, it should be flushed out at the first opportunity.

1921 Duesenbergs had the first hydraulic brakes on production cars. They use an alcohol water mix for brake fluid.
 
Since transmission fluid is hydraulic fluid, what would happen if it were put into a hydraulic brake system? Could you do it in a pinch just to get home?

Could you put brake fluid in an automatic transmission or ps pump for a short time?

What exactly is the difference between all of these hydraulic fluids?
 
DON'T DO IT!!!!!!

This is the BEST advice you'll hear on this.

Putting ATF in a brake system will require you to replace EVERY part in that system that has rubber/nitrolon components because of the swelling of these parts that will occur.

Likewise, but for different reasons, you should not use brake fluid in a system that calls for motor oil/ATF.

To answer your other question, brake fluid (DOT 3 and 4) is a "glycol" based fluid, ATF is a "petroleum" based fluid. They have two totally different chemical makeups and are not compatible with one another.

P.S. In the case of an emergency, you would do better by filling the brake cylinder with water or soda pop until you got to where that could be flushed out.
 
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