Changing Brake Fluid from DOT 4 to DOT 5

[Kelpie]

1. I read that :

 

" DOT3 or DOT4 brake fluid absorbs water and can absorb water from the air, which is why we should avoid opening the car's brake fluid reservoir. For the same reason, we should always keep containers of brake fluid tightly sealed.

 

DOT5 fluid does not absorb water. This means the boiling point will remain relatively stable, but it also means that any water that does get into the brake system will tend to form pure water pockets, which could cause brake corrosion.

 

Two other important things about brake fluid: DOT3 and DOT4 eat paint, so don't spill it on your car. Also, none of the different types of brake fluid should be mixed. They can react badly with each other and corrode our brake system."

 

2. Hence to use DOT 5, my current DOT 4 Brake fluid should be completely flush out and replace with DOT 5. Any Bros have done it before? any comments and advice? Is the process reversible? i.e. change back from DOT5 to DOT4?

 

Please advise us. Thank you very much.

 

Regards,

[Followthelaw]

Have been using DOT 3 for many years,so far so good. Any DOT,the owner shld also do a flush once a year.For good braking,install a brake vacumnn,really works.

[Nine_eleven]

stay away from DOT 5

 

if you really want, then use DOT 5.1. (5 and 5.1 are worlds apart)

 

ATE's DOT 4 fluids even outspec normal DOT 5.1s...

[Kelpie]

stay away from DOT 5

 

if you really want, then use DOT 5.1. (5 and 5.1 are worlds apart)

 

ATE's DOT 4 fluids even outspec normal DOT 5.1s...

 

1. Is there a good reason to stay away from 5? I'm trying to find an answer to this.

 

2. 4 and 5.1 are essentially the same.

 

Regards,

[Rskeisuke]

dot 5 is not compatible to dot 3/4 brake system. use dot 5.1 if you die die must have biggest number.

 

i quote from http://www.carbibles.com/brake_bible.html

 

 

"..DOT3/DOT4/DOT5.1 which are glycol (Polyalkylene Glycol Ether) based, and DOT5 which is silicone based. DOT3 and DOT4 fluids are interchangeable* - the only real difference is their boiling point. Theoretically you could interchange DOT4 and DOT5.1 fluids too but I wouldn't recommend it. DOT3/4/5.1 and DOT5 fluids cannot be mixed or interchanged under any circumstances. They mix like oil and water (ie. they don't) and the silicon based fluids can destroy the seals in brake systems which rely on the moisturiser additives that are present in DOT3/4/5.1 fluids."

[EventH]

got this from wiki

 

DOT 5 is one of several designations of brake fluid denoting a particular mixture of chemicals imparting specified ranges of boiling point.

 

DOT 5 is a silicone based brake fluid. It is not compatible with any polyethylene glycol based fluids. Mixing DOT 5 with other types of brake fluids will start a chemical reaction that will cause solids to precipitate out of the mixture and inhibit proper brake system function.

 

Unlike polyethylene glycol based fluids it is not hygroscopic, however this means that instead of being dissolved, any water in the system will eventually find its way to the lowest point in the brake line, corroding it, and potentially boiling and causing brake failure. Its major advantage over other forms of brake fluid is that it does not harm paint while the other forms of brake fluid do. It is widely used in the antique automobile arena.

[Yeobh]

Not much advantage at all with Dot5. Replacing yr exiting Dot 4 with Dot 5 may result in more damage to the seals and increase corrosion inside the steel brake pipes.

[Yeobh]

No need to flush every year if the brake fluid is still within spec. Get yr mech to do a moisture test before replacing.

Edited October 20, 2007 by Yeobh

[Cheerios]

doesn't mean new things are good things

[Nine_eleven]

stay away from DOT 5

 

if you really want, then use DOT 5.1. (5 and 5.1 are worlds apart)

 

ATE's DOT 4 fluids even outspec normal DOT 5.1s...

 

1. Is there a good reason to stay away from 5? I'm trying to find an answer to this.

many bros here have answered this qn liao...

 

2. 4 and 5.1 are essentially the same.

if they're essentially the same to you...then why change?

 

Regards,

[Kelpie]

Not much advantage at all with Dot5. Replacing yr exiting Dot 4 with Dot 5 may result in more damage to the seals and increase corrosion inside the steel brake pipes.

 

1. Thanks, almost there. I came across this one which has a better answer on DOT 5:

 

"Silicone Brake Fluids

In years past, all brake fluids were glycol. Then D.O.T. 5, a silicone fluid having a higher temperature rating, emerged, initially to meet the higher boiling point requirements of racing use. (Race car brake systems include oil-cooler-like heat exchangers and ceramic pads.) Silicone fluid was able to withstand the most heat of any brake fluid, so it earned a reputation as a racing brake fluid. However, silicone brake fluid has properties very different from glycol fluid, and has its own pros and cons. On the advantage side, silicone fluid will not harm paint or plastic, and does not aggressively attract additional moisture as glycol fluid does. On the disadvantage side however, silicone fluid aerates easily. Harley-Davison, one of the sole current OEM users of silicone fluid, warns buyers to let the fluid sit at least an hour before using it. The trip home in the saddlebag is enough to aerate silicone brake fluid until it looks like a freshly poured soft drink. Silicone fluid is also slightly more compressible than glycol fluid, does not change color to tip the user to its moisture content, and worst of all, neither accepts or disperses moisture, making systems using it more corrosion prone, and requiring much more frequent fluid changes. Silicone brake fluid also lacks glycol fluid's naturally occuring lubricity, making it incompatible with the mechanical valving in some antilock braking systems"

 

2. DOT 5 requires more frequent change due to a higher possibility of corrosion, which is still acceptable. However, DOT 5 may be incompatible with some ABS. This will be a big question and of greater concern.

 

3. Still, I don't know about the outcome of switching back from DOT 5 to 4.

 

Regards,

Edited October 20, 2007 by Kelpie

[Kelpie]

1. Is there a good reason to stay away from 5? I'm trying to find an answer to this.

many bros here have answered this qn liao...

 

2. 4 and 5.1 are essentially the same.

if they're essentially the same to you...then why change?

 

Regards,

 

What I'm saying 4 and 5.1 are sama sama. Since they are still not silicone based, no point changing from my current DOT 4 to 5.1.

 

Regards,

[Eyke]

if you don't drive like you are in a race then Dot 4 should be sufficient for your needs.

[Silver_blade]

Not much advantage at all with Dot5. Replacing yr exiting Dot 4 with Dot 5 may result in more damage to the seals and increase corrosion inside the steel brake pipes.

Assuming everything is stock...using Dot 5 for a dot 4 specific system, will cause more damage.

[Yeobh]

Pl check your handbook for recommendation. Not all brake pump seals can take silicon and vice versa.