How to change brake fluid?

[rockola1971]

It surprises me how much fluid it takes, especially since the brake lines are rather small diameter and the reservoir doesn't hold a lot. The ABS modual and MC/Booster must have large passages or something.

Dont forget the volume of fluid in the calipers all the way around too.

 

[gooffeyguy]

I know these trucks are long and wide, but my mustangs only take about 3 qts to do a complete flush, and the 33 hotrod only takes about 2 qts.

 

[iamdub]

The Tech 2 has an automatic brake bleed function. It uses the ABS Pump to "pump" the brake system instead of someone manually having to pump the brakes. Which is usually a necessary procedure because of the solenoids with the ABS manifold and those can trap air which is why the system cant be bled old school or usually even gravity bled.

I thought the standard ABS module was simply a bank of solenoids that pulsed opened to relieve pressure from the locked corner(s). I never knew it pumped anything. I know the StabiliTrak version of ABS has a pump on it because it actively applies pressure to some corners while relieving pressure from others. My questioning isn't to doubt you. I'm just kinda fascinated cuz I've never heard of this, but also never looked into it much.

After some reading, I see that the pumping action is a part of modern-day standard ABS since it has to reapply brake pressure to the wheel(s) it is modulating.

 

[iamdub]

We went through 6 quarts of brake fluid bleeding the brakes until the fluid came out clean, both the regular way and then with the Tech-2.

It does take a lot. But it's worth it to do a full and proper job and not contaminate the new fluid with the air (moisture) stuck in the system.

 

[iamdub]

I've heard the part about the pedal to the floor during some research. Do you know why it's bad to do that?

I do know because I learned by experiencing it firsthand, and way late in the game as I've done many brake jobs on all kinds of vehicles and never had a problem.

I did a full front and rear brake job on my Tahoe and when I got to the last corner (left front), the pedal started out like the previous three but suddenly wouldn't firm up. I thought I just had a large air bubble in it. Started the entire bleeding process all over again at the right rear and the pedal remained squishy. After some online reading, I decided that it had to be the master cylinder. Replacing it did indeed solve the problem, but what are the chances that it had just that amount of pedal strokes left in it that it failed half an hour before the parts store closed and on a night right before a 1500+ mile road trip?

Turns out, the cylinder wears within the usual range that the piston is stroked in during the many miles of normal driving. When you floor the brake pedal during bleeding, you're suddenly forcing this piston, with its aged seals, into the unworn/tighter area of the cylinder, stressing and possibly tearing them.

 

[wjburken]

It surprises me how much fluid it takes, especially since the brake lines are rather small diameter and the reservoir doesn't hold a lot. The ABS modual and MC/Booster must have large passages or something.

It’s not so much the actual contained volume in the system, it’s just that it takes that much to properly flush all the sediment out of the lines so the fluid is clear.

 

[Rocket Man]

It’s not so much the actual contained volume in the system, it’s just that it takes that much to properly flush all the sediment out of the lines so the fluid is clear.

This ^^^

 

[gooffeyguy]

It’s not so much the actual contained volume in the system, it’s just that it takes that much to properly flush all the sediment out of the lines so the fluid is clear.

This ^^^

And yet my other vehicles only take half the amount of fluid to get the same results

 

[Rocket Man]

And yet my other vehicles only take half the amount of fluid to get the same results

Maybe they never got as dirty in the first place? I looked and can’t find the brake fluid capacity for our trucks in the FSM.

 

[Rocket Man]

And yet my other vehicles only take half the amount of fluid to get the same results

Do you have hydro boost?