DOT 3 to DOT 5 • The Dodge Challenger Message Board

by **LITEMUP (Von)** » 17 Mar 2003 18:51

Can I blow all the DOT 3 brake fluid out of my car and replace it with DOT 5? I was told the only difference was that DOT 5 was not corosive. If thats true, I would love to replace mine.

But, if it was true, I would probably have heard about it before now.

by **Christer (Christer)** » 19 Mar 2003 18:56

I am not 100% sure but this is what I think: The only way to avoid rust in hydraulic brake systems is to change the brake fluid every now and then, maybe every second or third year (or something like that). It makes no difference if you use DOT 3 or DOT 5-fluid in this case. (Comment: I think that DOT 4 has been a standard fluid for the last years. I think it is a wise thing to do, to throw away your can of old DOT 3-fluid)

by **Glenn Jackson (Henner)** » 21 Mar 2003 2:04

yes I heard on hotrod tv or a show like that open cans of brake fluid sitting on the shelf collect moiture even if the lid is on tite. alway use a new can of fluid when doing brake work!!!

by **Christer (Christer)** » 22 Mar 2003 11:58

I found some information on:
http://www.shotimes.com/SHO3brakefluid.h tml

by **Christer (Christer)** » 22 Mar 2003 16:37

Here are two cuts from the site:
"DOT 5 is for silicone brake fluid. Silicone brake fluid (DOT 5) should be avoided because it is not compatible with regular brake fluid, it is hard to pour without introducing bubbles and thus results in soft pedal feel, and moisture still gets into your system and will pool in low areas like your calipers and encourage rapid corrosion. STAY AWAY!"

"That leaves DOT 3 and DOT 4 fluids. These fluids are compatible with each other and may be interchanged or mixed with no ill effects."

My comment: A thing to consider is that different makes absorbs moisture in different degree. Some of them quick and other slow (see the site above). Hey, it is a jungle out there!!!

by **Christer** » 06 Jan 2005 15:22

I have found some new information about this topic:

DOT5 is a silicone brake liquid. The big advantage with DOT 5 is that it doesn´t absorb moisture. That is why is very useful in cars who are garaged for long periods of time.

Are there any disadvatages with DOT5 then? Yes! It won´t under any circumstances mix with ordinary brake fluid (DOT3, DOT4 or DOT5.1). If you do it by mistake, then the complete brake system must be taken apart and washed with alcohol. All rubber sealings must be replace with new ones.

Silicone brake liquid will also give the brake pedal a bit more of "mushroom feel".