Replace DOT 3 with DOT 5 Brake Fluid

[kevmcrae]

Anyone ever changed from conventional DOT 3 to DOT 5 silicone based? I discovered my proportion valve had leaked over the winter and of course peeled the paint right off my inner fender!*^&$%^%^#!!! Bought a new chrome master cylinder with the proportion valve built in and thinking of changing to DOT 5 so I never have to worry about a brake leak ruining any paint. Had one guy tell me flush with alcohol, blow the lines out with air hose, and bleed with the new fluid?
Any other experience, advice, opinions?
Thanks
Kev

[rattle69]

Problem is dot 5 is racing fluid. It is to be changed always. It is not hydroscopic meaning meant to absorb water. If left in too long dot 5 will loose it's boiling point much faster that dot 3 or 4. It is used for racing only. Dot 5 is not recommended for every day use. Supercars come with dot 4...

[Rufton]

I would consider mineral oil for mild performance applications if entire system is brand new. Dot 3 exposed seals will be damaged by mineral oil. Not fond of Dot 5 because condensed H2O can pool and cause corrosion and performance issues. I use Dot 3 and change fluid every few years to avoid corrosion. Fresh Dot 3 has corrosion inhibitors. Dot 3 can damage paint. Quickly remove Dot 3 from paint w/ H20 or dish soap + H2O. Dot 5 can cause fish eyes when repainting. Not easy to completely flush system before changing to incompatible fluid.

[zeeklu]

I used dot 5 in my truck around 10 years ago. I replaced all the lines and every thing else. The fluid is still perfectly clean. My 2002 Harley came stock with it.
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[BigRed76]

My knowledge of the brake fluid differences is limited, however I've seen/heard of a lot more people converting to DOT 4 rather than DOT 5.

[Fldawg]

when i did my 4 wheel disc conversion i went with dot 3 synthetic , it's not suppose to attrach moisture like regular dot 3 , so far so good

[D.PASSMORE]

I run DOT 5 in my K20 and K5. No problems. All brand new components when I decided to use DOT 5.

[67 chevelle]

use dot 5.1 , not 5 , 5 is silicon and will not play well retrofiting your old system , 5.1 is great stuff being compatable with dot 3 and 4 , but has superior performance , higher boiling point , if you had a dot 3 system that was low you could top off with 5,1 , if you put 5 in it would destroy everything . i went thru a 3 year strugle with a brake issue in a 67 chevelle tryed every fluid , 5.1 was best , I tryed wrapin headers , lines , moving line and the brakes would lock after a few miles , even changed headers , turned out the rod from the booster was 1/16 of an inch too long into the master 2 5 cent washers between the booster and master solved the problem , since I have seen the same issue several times .

[Crabass]

Some info you might find interesting:

http://www.superchevy.com/technical/.../0509sc_fluid/

http://www.duntovmotors.com/tech-brake-fluid.php

[Bigdav160]

DOT 3, DOT 4, DOT 5.1 are glycol based fluid and will remove paint

DOT is silicone based and doesn't remove paint. It has some drawbacks but nothing I'd worry about.

[kevmcrae]

Thanks to all for your replies. And thanks to Crabass for the links. Gave me a lot more to think about.

[Tx Firefighter]

Originally Posted by rattle69

Problem is dot 5 is racing fluid. It is to be changed always. It is not hydroscopic meaning meant to absorb water. If left in too long dot 5 will loose it's boiling point much faster that dot 3 or 4. It is used for racing only. Dot 5 is not recommended for every day use. Supercars come with dot 4...

Every single vehicle in the Postal Service delivery fleet uses DOT5. All day every day. No racing, just work. It's good stuff.
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