I hope people realize that application of the brakes doesn't make brake fluid flow through the lines or various components. Sure...a very small amount of fluid movement happens. Applying the brakes simply pressurizes the fluid system enough to move caliper pistons the tiny distances needed to contact the rotors. Applying more brake pressure just pressurizes the fluid more. When an ABS module activates in an over-brake situation, the system of valves and pistons rapidly and repeatedly interrupts the high brake pressure enough to permit wheel movement. Fluid is not flowing through the module to any degree, but fluid pressure is rapidly fluctuating up and down by the module doing its work. I think there's a perception of the ABS module somehow allowing brake fluid to flow in a sort of bypass effect. Not true. Activating the ABS intentionally while riding is not an effective way to purge old existing brake fluid completely out of the module.

 

What I was wondering is there brake fluid in the abs pump that just sits there until abs engages, or does it cycle on its own, such as at start up? Otherwise fluid could sit in there for years, in theory.

 

This is me last year, unintentionally demonstrating what it looks like going from 55 to 0 with ABS. You feel pulsing in the brake lever, foot pedal, and your anus. 😳

 

Yes to all.

An abs system typically cycles upon startup, just self-check operations. Otherwise it sits there silently and sealed off via the valves.

The cycling of the valves and such upon startup does does not mix fluids well, though there is some small amount of mixing at the valves.

This is different than actuation of the abs during braking. Which will better mix fluids locally.

But this is still a far cry from using controlled actuation specifically to flush brake fluid through the abs unit.

 

Good description of how it works. Just activating the ABS by stomping on the brakes does not “ flush” the A B S module.

 

 

Bluesrider.df...WOW! I thought for sure you were going to hit! Nice job! ABS works.

 

Below is a good visual for the ABS system, and what was mentioned about the fluid remaining in the ABS unit, if not cycled when doing a flush.

The Red lines are what gets flushed when you do it the old fashioned way.
The Yellow lines are the very small amount of fluid in the valve unit that is stagnate, and not flushed without cycling the dump valve.
(The dark blue and brown lines are wires, and the light blue are the actuators.)

For the full video -
I do it the old fashioned way knowing at some point, the ABS will cycle before the next fluid change.

 

just as a preventive measure, when i do my 5k services, i hook up my scanner and do the abs activation. i'll do 2 or 3 (or more, depending) 5k services in the 1.5 - 2 years between brake fluid flushes. i also have a moisture detection device that i bought from amazon and will test the moisture content of my brake fluid at each service. sometimes it will go the full 2 years before it gets to the point where it is 'saturated', or it may reach it at the 1.5 year mark.

one thing to note is that the moisture content check is on the maintenance schedule. so if you don't do that check, and have a brake problem during the 2 year factory warranty period, the dealer could reject your warranty claim for not performing all necessary maintenance as required. it's worth the $10 to pick one up.

 

ABS was nice to have, but hats off my friend, you handled your **** there