DOT change (brake fluid)

[WhiteBeard]

Well, since I'm about to change my non functional rear brake caliper as well as changing over to SS brake line, I'm thinking I might as well change over from DOT 5.1 to DOT 5 and see how it turns out.
I understand it's important that the system be drained and cleaned of the old fluid before putting the other one in. I read of somebody using rubbing alcohol for this purpose, any other tricks?
Is it important that the seals get changed at the same time? I guess its a piece of mind thing and since it is the rear brake...   

[Pat Conlon]

If your existing rear brake seals are fine, then leave them alone. You will be fine with a *through* system flush.

[WhiteBeard]

If your existing rear brake seals are fine, then leave them alone. You will be fine with a *through* system flush.

OK, so just empty it of old 5.1 brake fluid, then flush with new DOT 5 and bleed?

Found this article on a V-twin site (http://www.v-twinforum.com/forums/engine-oils-lubrication/122482-dot4-dot-5-brake-fluids.html):

DOT3/DOT4 to DOT5 Brake Fluid Conversion
by Dave Barbieri


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Since I don't do 'conversions', I wanted to talk to some of our brake vendors (TX & CA) and get my facts straight. Here's the procedure recommended:


Use a turkey baster to suck all the old fluid out of the master cylinder reservoir. Fill the reservoir with rubbing alcohol. Get about 5 bottles; yer gonna need 'em. 8-P

Bleed the system, just like you would normally. Keep bleeding each wheel cylinder/caliper until only rubbing alcohol comes out. When all you see is only clean, clear rubbing alcohol, you're thru with the flushing.

Take all the brake lines loose at both ends. Use filtered, dry compressed air to blow out all alcohol. The lines must be free of all traces of alcohol.

Remove the master cylinder and wheel cylinders/calipers. Disassemble each component, clean thoroughly with either hot soapy water/hot water rinse or with a commercial non-filming brake cleaner. Dry each part and reassemble using DOT5 brake fluid as lubricant.

Components such as the combination valve will have alcohol in them from the flushing procedure. Blowing them out will be pretty touchy. Too much air and you 'blow out' the valve, too little and you don't get rid of the alcohol.

Re-install all the parts, fill the reservoir with DOT5 fluid, and bleed as normal.
There's not complete agreement on how DOT5 reacts with DOT3/4. Some tech reps said it forms a gummy residue that affects brake action. Two stated that the DOT5 would simply 'flush out' any traces of alcohol/DOT3/4 during the bleeding process. Since there's not 100% agreement, (and I'm both anal-retentive and paranoid when it comes to brakes), I listed the full procedure.

Do you really, reeeelly wanna do this? DOT5 is typically used in heavy eqyuipment, military vehicles, and (some) antique vehicles. All share the same characteristic of sitting for long periods of time. DOT5 gets rid of any concern about moisture absorption while sitting idle.

DOT5 is expensive and a PITA; I think you'll spend a lot of time and $$, only to be disappointed with the actual performance gains

As the quoted forum post said, I have no idea of this guys credibility.
And if you, Pat, has done it the simple way and made it just fine so far (which I know for a fact by reading your answers in earlier posts), then I am not worried at all.

Thanks and ride safe,
Nat

[grannyknot]

I have done this a few times, Methal Hydrate  is what I have always used, cheaper than rubbing alcohol.
Just make sure that the lines are dry, keep the compressed air flowing until nothing is coming out of the lines.
Then add the Silicone.