Volfy
1000 Posts Club!
I myself am not too concerned about the small volume of brake fluid that is trapped behind the ABS solenoid valve(s). I say this even though I have tool that allow exactly this for some of my vehicles... my BMW and Triumph motorcycle specifically. I don't even bother using the tool every time I bleed my bikes' brakes, for a few reasons:
1. The volume trapped is typically very tiny. This is especially true on a car/truck, where that trapped volume is much smaller as a % of the overall brake fluid volume... compared to that of a motorcycle braking system. Flushing the rest of the circuits probably displaces 95+% of the overall brake fluid volume. That means most of the fluid is now refreshed.
2. The fluid that is the most important is what's inside the brake calipers, where it is likely to be subjected to high temp and, therefore, needs to have that higher DRY boiling point, to prevent vapor lock. The ABS module is typically wayyy upstream, near the master cylinder, where it is much less likely to see high temps.
3. If I really wanted to "refresh" that small trapped volume behind the ABS solenoid valve, all I have to do is to activate the ABS system, right after I've flushed the brake fluid. This opens up to ABS solenoid valve and even though the ABS pump will only run a short period of time, it is generally long enough to push the small volume of trapped brake fluid out and replace it with fresh fluid. Yeah, the older fluid will mix with new, but again, the volume is small enough that, overall, the entrained moisture content in the system is diluted down to a safe level - especially for being mostly upstream near the master cylinder.
Practically speaking, it isn't such a bad idea for most drivers to test their ABS system periodically and to know what it sounds/feels like - in a controlled environment of the driver's choosing. Better that than learning that in an emergency where your (family's) safety might depend on it.
1. The volume trapped is typically very tiny. This is especially true on a car/truck, where that trapped volume is much smaller as a % of the overall brake fluid volume... compared to that of a motorcycle braking system. Flushing the rest of the circuits probably displaces 95+% of the overall brake fluid volume. That means most of the fluid is now refreshed.
2. The fluid that is the most important is what's inside the brake calipers, where it is likely to be subjected to high temp and, therefore, needs to have that higher DRY boiling point, to prevent vapor lock. The ABS module is typically wayyy upstream, near the master cylinder, where it is much less likely to see high temps.
3. If I really wanted to "refresh" that small trapped volume behind the ABS solenoid valve, all I have to do is to activate the ABS system, right after I've flushed the brake fluid. This opens up to ABS solenoid valve and even though the ABS pump will only run a short period of time, it is generally long enough to push the small volume of trapped brake fluid out and replace it with fresh fluid. Yeah, the older fluid will mix with new, but again, the volume is small enough that, overall, the entrained moisture content in the system is diluted down to a safe level - especially for being mostly upstream near the master cylinder.
Practically speaking, it isn't such a bad idea for most drivers to test their ABS system periodically and to know what it sounds/feels like - in a controlled environment of the driver's choosing. Better that than learning that in an emergency where your (family's) safety might depend on it.
