Funky Rear Brake Hose Replacement

[malloy]

Several threads go on about the lousy black rubber hose between the rear reservoir and master cylinder. Apparently it degrades and causes the brake fluid to turn black. Well, I'm there with that . The dealer says they all do that and a bleed is not scheduled for a year = could care less. That murky fluid can't be doing any good down line. Funny, though, how there is nothing wrong up front - crystal clear - go figure.

Has anyone found a good replacement for this hose, one that keeps the fluid clear?

I notice that the front hoses are fixed with Helix (sp?) type spring clamps but the rear hose has those one time type clamps, unless you have the fancy tool for them. What clamps are anyone using if/when they replace the rear hoses?

Much obliged .

[JRWooden]

The inside of the line does not leach stuff into the fluid for very long.

A flush now, and another one in a few months and the fluid will then remain clear (at least it has on my bike which is now about 3.5 yrs old) ... so I would go that way instead.

The flush is not hard to do, but obviously something you do not want to screw up

[malloy]

Thanks, JR! Mixed info on whether one needs to reset the ABS at the dealer or with a GS911 when bleeding an ABS equipped bike. Any comments on that issue? I've done a fair amount of bleeding on non ABS bikes but this is holding me up.

Much obliged.

[Apostolos]

After one flush my fluid got clear never to get dark again.

No special process or resetting needed for the abs. I used a mityvac. Works great.

God bless,
David

[malloy]

Thanks Apostolos. Getting the mity-vac out now.

[L.B.S.]

F800S and ST's have exactly the same thing, and from right off the boat and onto the showroom floor. No real length of time required for the fluid to turn dark, they come that way.

It looks almost like a dye leaching out of the rubber, not so much actual deteriorated rubber particulate, and it doesn't appear to ever come back once a flush is done.

When you buy the bike and point the dark fluid out, the Dealer says: "It's nothing, they're all like that, don't worry about it, perfecly fine, in no way effects anything. Please sign the purchase agreement here, Sir."

When you take your bike in for service, or try to sell/trade the bike for another model, the Dealer says: "OMG look at that brake fluid! It's hideous! We will have to flush that out immediately! Please sign the invoice here, Sir."

[JoelWisman]

Dido others. it's from the hose between the master and reservoir. BMW studied it and it is NOT harmful. I never once had to replace a rear caliper on a K7x bike. It is unsightly and a couple of flushes will make the unsightliness go away permanently.

P.S. it is never too early for the first flush. These bikes are shipped in cardboard crates in ISO containers on freighters. I have cleaned salt water deposits off of the body work at PDI more times then I care to remember.....

P.S.S. Clean looking fluid means nothing. Brake fluid is hygroscopic and is in a system that is not sealed. The only way to know how contaminated your fluid is, is with a $400 tester. Often black fluid is fine and frequently clear fluid is filled with water. That water corrodes the caliper piston pucks and bores. Corrosion byproducts are heavier then brake fluid so will hang out in the caliper never showing up in the reservoir.

Don't be concerned about the appearance go the brake fluid, but be concerned if you haven't flushed the fluid in over two years (every year for those in humid areas) and if it were me i'd also flush the fluid at the first service.

[malloy]

Thanks for the information LBS & Joel. I guess the by now BLACK fluid offended my senses - it shouldn't be that way, etc. So bled it I did and with seemingly no adverse ABS consequences. Took a short ride and all seems well. It's nice and clean now so I can sleep better. I'll probably do the front soon, just for grins.

[johnparjr]

Same as everyone else I flushed it after I rode home on the bike 5 min job done and it hasn't come back.

[JRWooden]

Originally Posted by malloy

Thanks, JR! Mixed info on whether one needs to reset the ABS at the dealer or with a GS911 when bleeding an ABS equipped bike. Any comments on that issue? I've done a fair amount of bleeding on non ABS bikes but this is holding me up.

Much obliged.

It may be the case that other BMWs need an ABS reset when flushing the system which confuses things, but I have found no data that would support the need to do so with the F800/F658GS twin bikes. I have flushed my system 4 or 5 times and not needed to reset with GS-911 or at the dealer. The front brake is a bit trickier due to need to flush at both the master cylinder and the caliper.

I flush at least once a year ... when I replace brake pads, or just for grins if the pads are OK.

I have one recommendation to add ... that is that when you compress the piston into the caliper that instead of just opening the master cylinder and then pressing the piston back into the caliper (thus pushing old fluid back into the ABS controller) I put a piece of tubing on the bleed screww and then open the bleed screw and compress the piston... doing it this way drains the old fluid out of the system thru the tube instead of pushing it "backwards" into the system.

Just "food for thought"

[fiwi]

Is there a specific mityvac model that people usually use on their bike?

[JoelWisman]

Originally Posted by fiwi

Is there a specific mityvac model that people usually use on their bike?

Any model will work okay for changing out fluid, but to combat softness in the brakes due to air inclusion, vacuum bleeding sucks.

By creating a partial vacuum in the hydraulic system air bubbles expand and become more difficult to pass through the system and remove from nooks and crannies.

Due to the fact that vacuum bleeders suck air continuously through the bleeder nipple threads, you also can't tell when most the air is out of the system (you will never get all of it out with a vacuum bleeder) nor can you tell approximately where the air was trapped in the system and hence where to look for how air got in.

If you can find and afford it, a pressure bleeder is a massively better tool for hydraulic system maintenance.

P.S. I have never seen a BMW who's brakes I couldn't massively firm up right out of the crate with pressure bleeding. Every BMW that has not been skillfully pressure bled has air in the system that the factory cheerfully left there for your braking enjoyment.

Lastly if you use any form of petroleum or silicone product to keep air from being sucked past the bleeder nipple threads during vacuum bleeding, you are shortening the life of every seal in your brake hydraulic system as NONE of them are petroleum or silicon compatible.

[malloy]

Good info JR & Joel. Agree about bleeding them right out of the box. BS on BMW and/or dealers for not doing it before delivery.

And these pressure bleeders of which you speak Joel; available at Walmart no doubt for $19.95 ?

[JRWooden]

At one time I worked in a shop that had a pressure bleeder .... it was the BEST

One night somebody forgot to release the pressure on it and we came in the next morning and it had pissed the better part of a gallon of brake fluid all over the shop floor.... the service manager was ..... ummmmmm ... not happy

getting the right adapter plates was always the challenge in our shop............. we ended up making several ....

[Hucker]

So, if one was looking for such a pressure bleeder system to maintain 2 F800's, one would be well off buying...

Joel, you've made some great suggestions on tools in the past. Don't let a brother down now...

Thanks.