When the brake fluid is an unknown

RonKZ650 wrote:

I put dot5 in all my motorcyles way back in the mid 80s and have had zero problems. The way I flush brake fluid which I'm sure is not by the book, is to pump out the old fluid until the master cylinder is 95% empty, then fill with dot5, pump until 95% empty again, add dot5. Do this until dot5 can be seen coming nice and clear (or blue) out of the caliper. Flushed and ready to go and no fighting bleeding the lines. Never had a problem of any kind doing this procedure. Of course as pads wear, more brake fluid is used to take up space in the caliper to keep the pads adjusted, so this may explain why the fluid has gotten lower.

what ron said!

I did what Ron says a few years back (need to do it again) and as he says, I had no problem but when finished my brake feel was much firmer! Very simple procedure...

duncan wrote:

i just read a good article on DOT3/4/5 yesterday:

www.motorcycleproject.com/motorcycle/text/cows-brakefluid.html

...

That was an awesome article! I was pondering the same question (DOT 3/4 vs Dot 5). This article points out that Dot 3/4 is clearly the best choice for most riders. I just bought a quart of Valvoline full snythetic dot4 for about $6. I have all new lines and totally rebuilt mastercylinders and calipers. It would have been a good time to go to DOT 5 but it just doesn't seem worth it.

I would recommend flushing the brake system with alcohol and then filling with a good quality Dot 3/4.

Alcohol?? OK....I'm not a chemist, so am curious about this? Honest....just curious.....

79MKII wrote:

I would recommend flushing the brake system with alcohol and then filling with a good quality Dot 3/4.

:blink:
I would recommend flushing the brake system with new fresh brake fluid, preferably DOT 4.
I can't find any source that recommends anything but new brake fluid going into a brake system.

indykaw77 wrote:

Alcohol?? OK....I'm not a chemist, so am curious about this? Honest....just curious.....

It is recommended to use alcohol (isopropyl or ethyl) for brake part cleaning according to the Kaw factory manual. It states that it will not harm any of the rubber parts as would any petroleum-based product. I think I also read somewhere that glycol (the base for DOT3 and 4) is alcohol-soluable. Not 100% sure on that one though.

Yeah, but that's for parts cleaning. Don't run it through your system. Isopropyl Alcohol from the drug store is usually 50 to 70% water. And residual left in the system will just pre-contaminate it.:blink:
Flush the system with brake fluid. Clean parts with rubbing alcohol, then dry them thoroughly. Messing up your brakes can kill you or someone you love. Or maybe even someone you don't know.

pstrbrc wrote:

Yeah, but that's for parts cleaning. Don't run it through your system. Isopropyl Alcohol from the drug store is usually 50 to 70% water. And residual left in the system will just pre-contaminate it.:blink:
Flush the system with brake fluid. Clean parts with rubbing alcohol, then dry them thoroughly. Messing up your brakes can kill you or someone you love. Or maybe even someone you don't know.

Do an internet search on "flush brakes with alcohol", you'll see that it is recommended by many sources for Dot3/4 fluid.

pstrbrc wrote:

Yeah, but that's for parts cleaning. Don't run it through your system. Isopropyl Alcohol from the drug store is usually 50 to 70% water. And residual left in the system will just pre-contaminate it.:blink:
Flush the system with brake fluid. Clean parts with rubbing alcohol, then dry them thoroughly. Messing up your brakes can kill you or someone you love. Or maybe even someone you don't know.

I just caught the 50-70% water part:blink: Where did you get that from? I don't think they can all it isopropyl alcohol if it only has 30% isopropyl.

From Wikipedia (this covers the water in the brake system part):
..."It is also used as a gasoline additive for dissolving water or ice in fuel lines. Although Isopropanol is sometimes sold as "Isopropyl Rubbing Alcohol, 70%", there is no isopropyl alcohol in the United States Pharmacopeia formula for Rubbing alcohol, U.S.P.. It is used as a disinfectant, and is a common solvent.

Isopropanol is a major ingredient in "dry-gas" fuel additive. In significant quantities, water is a problem in fuel tanks as it separates from the gasoline and can freeze in the supply lines at cold temperatures. The isopropanol does not remove the water from the gasoline. Rather, the isopropanol solubilizes the water in the gasoline. Once soluble, the water does not pose the same risk as insoluble water as it will no longer accumulate in the supply lines and freeze."

79MKII wrote:

I just caught the 50-70% water part:blink: Where did you get that from? I don't think they can all it isopropyl alcohol if it only has 30% isopropyl.

Oops! sorry. my bad. To be sold as Isopropyl alcohol in the US it can be no more than 50% water. It's customarily no more than 70% alcohol. I have a bottle in the cupboard that's 50% alcohol, and one that's 70%. That means that one bottle is 50% water, and the other is 30% water. Oh, and, yes, I CAN find knuckleheads on the internet that recommend flushing a brake system with isopropyl alcohol, but no manufacturers of brake components. Raysbestos makes it clear that if a system has been contaminated by foreign fluids (atf, etc.) that all components containing rubber parts (master cylinder, hoses, brake cylinders) be replaced and the steel lines only be flushed with alcohol before reusing.
But I can't find any reputable (meaning, they could be tracked down and sued) source recommending isopropyl alcohol as a brake system flush. If you can find one, post it.

OK, OK, I'm not getting into a flame war here, preach. What I should have made clear is that the lines should be broken free and flushed with alcohol. All of the other parts can also be flushed with alcohol. I would then follow up with compressed air. Isopropyl actually clears the system of water and won't harm the rubber components. For a normal flush, where the type and condition of fluid is known, the mastery cylinder should be emptied (with a baster type suction device) and new DOT 4 fluid added until the fluid at the bleeder is clear and clean. I just thought in this case that the system could be cleaned for a fresh start. It would mean a lot more work, but like you said, brakes aren't something to mess with. I think we're on the same page here.

---- replaced all rubber parts, so alcohol attaching rubber wasn't a concern