Changing from DOT 3 to DOT 5
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Road Warrior
Joined: Mar 2007
Posts: 1,959
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From: Florida
Changing from DOT 3 to DOT 5
My rear brakes have DOT 5 fluid, and that makes it maintenance free. My front is DOT 3, and I have to bleed them 2 or 3 times a year. I've read a little, and apparently the two don't play well together, and can cause problems when putting one over another. Anyone change from 3 to 5? Do the lines have to be flushed out with something? Thanks.
Seasoned HDF Member
Joined: Aug 2007
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From: NW AR
I've changed 2 Toyota clutch systems from 3 to 5. One was when I had to do a full replacement on the MC and SC. I flushed the line with brake cleaner, then blew it out with air. The other was a MC only. I opened the bleeder on the slave cylinder, put brake cleaner in the line and worked that through until it was clean at the slave cylinder, blew it out with air, then filled and flushed several times with DoT 5. Both systems have been working fine.
Novice
Joined: May 2011
Posts: 19
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From: Knoxville, TN
When changing from one to another it is highly recommended that you replace all components that fluid touches. I have heard of some people getting lucky and not having to change lines after a intensive brake cleaner flush. Not something that I would play with myself unless braking isn't that big of a deal for you.
Seasoned HDF Member
Joined: Aug 2011
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From: SW Ohio
DOT 5 isn't maintenance free. Water can and will contaminate the system as it isn't completely air tight. The water won't contaminate the DOT 5 fluid because it isn't hydroscopic but the water will collect in the system and cause corrosion issues if not changed regularly.
DOT 5 also compresses much easier than glycol based 3, 4 and 5.1 leading to a softer lever or pedal. It has its advantages, but maintenance free it isn't.
DOT 5 also compresses much easier than glycol based 3, 4 and 5.1 leading to a softer lever or pedal. It has its advantages, but maintenance free it isn't.
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Road Warrior
Joined: Mar 2007
Posts: 1,959
Likes: 2
From: Florida
Thanks for the great input! I guess I'll just keep doing what I've been doing, sounds like it's more trouble than it's worth. I haven't done anything with the rear brakes since I got the bike 7+ years ago, except I changed the pads once. Maybe I'll bleed them!
Seasoned HDF Member
Joined: Aug 2007
Posts: 8,201
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From: NW AR
If it was me, I'd swap it out to 5 after flushing with brake cleaner, then 5. I'm a big believer in 5. I've been swapping all my clutch hydraulics to 5 when I service them.
I pulled my rear brake apart after literally not touching it for ~15 years, not even checking the fluid level. I fully expected the caliper to be garbage. It looked almost new, with just some light scuffing.
I pulled my rear brake apart after literally not touching it for ~15 years, not even checking the fluid level. I fully expected the caliper to be garbage. It looked almost new, with just some light scuffing.
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Road Warrior
Joined: Mar 2007
Posts: 1,959
Likes: 2
From: Florida
Well, it really doesn't sound that bad. Maybe I will after all. I may have been the one that screwed up to begin with by adding 3 to it when I got it. I ended up with green sludge plugging the lines and MC. That was a long time ago.
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Seasoned HDF Member
Joined: Nov 2009
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From: Farmington ,MS
Don't think so...for all practical purposes liquids are not compressible...never noticed any difference in pedal/lever.