Brake fluid, DOT 3 vs DOT 5
Tourer
Joined: Apr 2010
Posts: 465
Likes: 5
From: Cleveland, Ohio
Not saying this is the right thing to do by any means.
I bought a used 05 Sportster from a dealer. The cylinder caps both say to use DOT 5. I bought some DOT 5 and went to add some to the cylinders and lo and behold there was either DOT 3 or 4 in there.
I don't know how long it has been like this but as far as leaking goes there isn't any. The brakes also seem to function fine as well.
I bought a used 05 Sportster from a dealer. The cylinder caps both say to use DOT 5. I bought some DOT 5 and went to add some to the cylinders and lo and behold there was either DOT 3 or 4 in there.
I don't know how long it has been like this but as far as leaking goes there isn't any. The brakes also seem to function fine as well.
Seasoned HDF Member
Joined: Nov 2009
Posts: 15,705
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From: Farmington ,MS
My 84 came with Dot 5 from the factory. Once the seals have had Dot 3 on them, Dot 5 will make them deteriorate. If you rebuild the system with new rubber you could run Dot 5.
http://listproc.ucdavis.edu/archives...0901/0051.html
http://listproc.ucdavis.edu/archives...0901/0051.html
Thread Starter
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Cruiser
Joined: Apr 2010
Posts: 133
Likes: 0
From: West Central Indiana
Okay. The op now says he "thinks" he put dot 3 in the rear system. After talking with a local mechanic here's what I'm going to do. I already have the rear master cylinder off. I'll be flushing everything out with brake clean, lots of it, then then using some dot 5 as a flush also. Then reassemble everything, fill it up with dot 5, bleed the system and go on my merry way. The mechanic says that even IF I have a problem down the road there will be warning signs and that it wouldn't be an instantaneous failure. He says he has done this on a few bikes in the last 4 or 5 years and has yet to have any problems or complaints.
Both Harley and Clymer say bikes built after Sept. 1976 must use dot 5. By the way, has anyone bought any of this stuff? It ain't cheap. 8.99 for a small bottle of it.
Both Harley and Clymer say bikes built after Sept. 1976 must use dot 5. By the way, has anyone bought any of this stuff? It ain't cheap. 8.99 for a small bottle of it.
Outstanding HDF Member
Joined: Oct 2007
Posts: 3,178
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From: 50 Miles North N.Y.C.
Im just saying back in the early 1980's. The US Post Office and US Army National Guard. Changed out all there Cars and Trucks from Dot 3 to Dot 5. Just bleed them out with a power bleeder. Did not change out and break componits before the change. I bleed all my cars from 3 to 5 at that time. Had no problems. No leaks. The reason for the change over was lower mantanice . As Dot 3 is alcohol based Dot 5 silicon based. Dot 3 atracks moisture. Dot 5 does not. There are different boiling points between Dot 3 and 5. There are a lot of urbin legends on Dot 3 verices Dot 5. Just like there are on different Motor Oils. Dot 5 won't mess up your paint job if spilled on it. Dot 3 will discolor it. I don't know the difference Between Dot 3 or 4 would like to. Could it be the boiling point? I know Dot 3 and 4 are alcohol based.
Seasoned HDF Member
Joined: Dec 2004
Posts: 11,068
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From: Texas! Ya mean there's someplace else?
Don't mix them; they react with each other and more-or-less congeal. DOT 5 doesn't provide as good a "feel" as DOT 3 or 4, but it doesn't suck up moisture. Doing as you said - drain, flush, and fill - will work fine.
Ultimate HDF Member
Joined: Jan 2007
Posts: 8,750
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From: back home in Michigan
And they are color coded.
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Outstanding HDF Member
Joined: Oct 2007
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From: 50 Miles North N.Y.C.
Tourer
Joined: Apr 2010
Posts: 465
Likes: 5
From: Cleveland, Ohio
Upon further investigation on my bike I actually do have DOT 5 in there (Got the bike about a month ago)
Anyway the color is what threw me off. I bought some DOT 5 from Harley and it was purple and the fluid I had in there was a yellowish color.
So don't go by the color to find out what it is.
I did a test with the fluid in there. I took out a small about and put it in a shot glass. I then added a few drops of water in it. If it is DOT5 the water will not mix and sink to the bottom in what looks like a little bubble. If it is DOT3/4 then the water will mix with it and you will not be able to tell there is water in there that you added.
Anyway the color is what threw me off. I bought some DOT 5 from Harley and it was purple and the fluid I had in there was a yellowish color.
So don't go by the color to find out what it is.
I did a test with the fluid in there. I took out a small about and put it in a shot glass. I then added a few drops of water in it. If it is DOT5 the water will not mix and sink to the bottom in what looks like a little bubble. If it is DOT3/4 then the water will mix with it and you will not be able to tell there is water in there that you added.
Last edited by dibe; May 6, 2010 at 11:02 AM.