Are ABS brakes user serviceable?

[kenvil1]

I really admire the V7 for it's apparent ease of service (says a non-owner), but can the average owner/rider replace their own brake fluid on ABS equipped models, or do they need a qualified mechanic to perform the work?
I like the simplicity of a single caliper per master cylinder, but ABS throws a wrench into this basic system (pun alert). Also, has anyone contemplated retrofitting a non-ABS brake system on their V7II, or is the idea simply foolhardy?

[Kentktk]

I really admire the V7 for it's apparent ease of service (says a non-owner), but can the average owner/rider replace their own brake fluid on ABS equipped models, or do they need a qualified mechanic to perform the work?
I like the simplicity of a single caliper per master cylinder, but ABS throws a wrench into this basic system (pun alert). Also, has anyone contemplated retrofitting a non-ABS brake system on their V7II, or is the idea simply foolhardy?

Brake fluid and pads owner can do just like before ABS. Pull the ABS controller fuse and you have will non-ABS brakes

[Muzz]

Have no idea on the V711, but my mate who has a K1200 BMW was told that the year he bought was good because you could service the ABS, whereas on the later years you couldn't. No idea on the difference.

[guzzisteve]

Just buy an earlier version, plenty unsold new models.

[pete roper]

As long as you don't get air in the system you can bleed them the same as any non ABS system BUT....

The problem arises in the fact that there is a fluid reservoir in the ABS pump and this won't be purged with normal bleeding. While PADS has a specific function for activating and purging the pump, (I don't know about aftermarket systems.) you can purge the pump simply by once you've bled the brakes 'Conventionally' taking the bike somewhere safe and getting the ABS to kick in a few times. This will circulate the old fluid in the pump back into the main system and then another 'Conventional' bleed will remove the stale fluid from the system entirely. If however you get air in the pump you will have to have the *Stimulated* purge function to clear it out as the brakes won't be effective enough to get the ABS to kick in.

Pete

[Kev m]

Then there is the simple fact that brake fluid replacement intervals are generally ridiculously conservative. You could likely go a decade without issue.

[kenvil1]

Brake fluid should be replaced every two years, apparently, although this guideline is probably in the better interest of the manufacturers than the owners. I know my decades-old Honda had a kinda sludge in the front master cylinder and the braking seemed fine.

[Kev m]

Brake fluid should be replaced every two years, apparently, although this guideline is probably in the better interest of the manufacturers than the owners. I know my decades-old Honda had a kinda sludge in the front master cylinder and the braking seemed fine.

Exactly, that's my point.

For decades most vehicles in the US has literally NO recommendation to EVER replace brake fluid.

It's becoming more popular, but I'd venture the guess that the vast majority of vehicles on the roads here have never had, and never will have, their brake fluid replaced.

[sib]

It's interesting that the latest workshop manual for the V7II ABS (2Q000105) makes no mention of a brake fluid reservoir within the ABS control module, nor any instructions about how to bleed it.  Has anyone actually disassembled one of these units to verify that there's a brake fluid reservoir present, or any significant dead space that wouldn't be flushed by a thorough brake flush?  Thanks for any info.

[kenvil1]

I'd venture the guess that the vast majority of vehicles on the roads here have never had, and never will have, their brake fluid replaced.

The same can probably be said about fork oil, but I'd kinda expect Guzzi owners to be more proactive than most. What's the saying? "Moto Guzzi: Making mechanics out of owners for over 75 years"

[Kev m]

The same can probably be said about fork oil, but I'd kinda expect Guzzi owners to be more proactive than most. What's the saying? "Moto Guzzi: Making mechanics out of owners for over 75 years"

Well it's interesting you would say that.

I'm writing a Sportster repair manual now and in just the short last decade recommendations changed from every 20k miles to every 50k miles with no time limit.

I'd say that's another example of something I ignored when manufacturers suggested something too conservative and later changed at many times over the recommendation to find the fluid didn't seem emulsified or otherwise contaminated.

[sib]

I would propose that one reason for the longer change intervals these days is that the parts have improved to lower the rate of contamination of the fluids.  For brakes, water infiltration into the very hygroscopic brake fluid is probably the primary reason for the need to replace the fluid.  Water-laden brake fluid can rust metal brake components and it can boil when heated during heavy braking.  There are only so many ways that water can get into the fluid:  air leaks around the non-pressurized fluid reservoir cap, and diffusion of water vapor through the rubber of the piston seals and even the brake hose itself.  Rubber hose composition has changed to lower vapor diffusion, partly due to more stringent evaporative emissions regulations, and I woudn't be surprised if the rubber in the caliper piston seals has also improved to lower water vapor incursion.

[kenvil1]

my mate who has a K1200 BMW was told that the year he bought was good because you could service the ABS, whereas on the later years you couldn't.

Some BMW K models use servo motors as part of their ABS systems. Whole other ball game.

[Kentktk]

I would venture to guess most cars on the road have the same brake fluid that it came off the showroom floor with. Be that 2 years 10 years or many more.

[Muzz]

 it can boil when heated during heavy braking.
 
Many years ago there was a certain hill that claimed many victims out here. It was back in the day when they had single reservoir master cylinders etc. Any survivors said their brakes failed, but when the experts checked they could find nothing wrong. Later it was found that it was the result of heat being transferred to the brake fluid, and if the brake fluid had not been changed for a long time the water in it boiled and turned to steam, which lead to a loss of brake pressure. By the time the wreckage was examined the steam had turned back to water and had been reabsorbed by the brake fluid (which is an alchohol).

There are only so many ways that water can get into the fluid:  air leaks around the non-pressurized fluid reservoir cap, and diffusion of water vapor through the rubber of the piston seals and even the brake hose itself.  Rubber hose composition has changed to lower vapor diffusion, partly due to more stringent evaporative emissions regulations, and I woudn't be surprised if the rubber in the caliper piston seals has also improved to lower water vapor incursion.

The very act of the brakes working will suck a small amount of air into the master cylinder reservoir. Probably small on a full disc braked car but one with drums on the back a bit larger. Water vapour will be absorbed by the brake fluid unless it is synthetic.

Good practice to change the fluid at the prescribed times. I think the 4.1 is the synthetic one, not sure on that, but before you think that would be the way to go it can sometimes be an absolute bitch to get them not to leak at the seals.

[Kev m]

The very act of the brakes working will suck a small amount of air into the master cylinder reservoir. Probably small on a full disc braked car but one with drums on the back a bit larger. Water vapour will be absorbed by the brake fluid unless it is synthetic.

Good practice to change the fluid at the prescribed times. I think the 4.1 is the synthetic one, not sure on that, but before you think that would be the way to go it can sometimes be an absolute bitch to get them not to leak at the seals.

Of course many bikes have a rubber bladder diaphragm to isolate the brake fluid in the reservoir from the incoming air that displaces the volume of fluid transferred to the lines.

[tonyduc]

Bought My 2011 Stelvio new in 2014, I picked it up with my truck and after unloading at home found that the rear brake did not work. Checked the reservoir and found that the fluid was almost black, after several bleeds brake was fine. So from just sitting 3 years in a brand new bike in this case the brake fluid did go bad. Ironically the front fluid was fine, and 2 years later rear brake still fine.

[kenvil1]

The moral of the story, however, is to not neglect your brakes. Lots of go is nice, but a lack of whoa is not.

[pehayes]

Having a little air in the master reservoir is not an issue.  It is the MOISTURE in that air which is an issue.  Brake fluid is very hydroscopic; meaning is literally sucks water vapor out of raw air.  The presence of moisture dissolved into the brake fluid drops it boiling point dramatically.  Brake hard several times and the parts can get quite hot.  Boiling brake fluid makes bubbles and fades the brakes.  The purpose of the rubber bellows or bladder is to prevent a constant resupply of moist air above the fluid level.  The bladder isolates that captured bubble of air and it remains 'dried' after the brake fluid sucks its moisture.  No way to get more moisture in until you remove the cap and bellows.  One of the reasons that most master cylinder caps and brake fluid cans recommend to always use fresh fluid from a newly opened can.

Patrick Hayes
Fremont CA

[sdcr]

Just buy an earlier version, plenty unsold new models.

Where?   

[Kev m]

Bought My 2011 Stelvio new in 2014, I picked it up with my truck and after unloading at home found that the rear brake did not work. Checked the reservoir and found that the fluid was almost black, after several bleeds brake was fine. So from just sitting 3 years in a brand new bike in this case the brake fluid did go bad. Ironically the front fluid was fine, and 2 years later rear brake still fine.

Considering the vast majority of vehicles on the road have never had a brake fluid change I'm going to guess you're talking about an absolute anomaly.

[Kev m]

Having a little air in the master reservoir is not an issue.  It is the MOISTURE in that air which is an issue.  Brake fluid is very hydroscopic; meaning is literally sucks water vapor out of raw air.  The presence of moisture dissolved into the brake fluid drops it boiling point dramatically.  Brake hard several times and the parts can get quite hot.  Boiling brake fluid makes bubbles and fades the brakes.  The purpose of the rubber bellows or bladder is to prevent a constant resupply of moist air above the fluid level.  The bladder isolates that captured bubble of air and it remains 'dried' after the brake fluid sucks its moisture.  No way to get more moisture in until you remove the cap and bellows.  One of the reasons that most master cylinder caps and brake fluid cans recommend to always use fresh fluid from a newly opened can.

Patrick Hayes
Fremont CA

HyGroscopic (I used to make the same mistake all the time).

And there's no constant resupply. There's not a lot of volume of air moving in and out.

As a matter of fact the volume of air is generally so small that it is probably not the biggest cause if there is excessive moisture contamination in otherwise normal usage.