brake pedal to the floor when crusing on the freeway

[fastezz]

OK when I am crusing on the freeway my pedal goes to the floor and I have to pump the pedal to get pressure but its fine around city, have any idea what it is??
Thanks
Ryan

 

[spirol]

It could be:
1. Leaking master cylinder (internal/external). To check, clamp the 4 brake lines and pump the brakes, if it goes to the floor then the master cylinder is leaking.

2. Contaminated Brake Fluid. It cause spongy brake in which the brake fluid needs to be replaced. Use DOT3 or DOT4 for brake fluid. Flush, refill and bleed the lines.

3. Air in the brake lines. Bleed the lines. To properly bleed, Start bleeding the caliper that is the farthers away from the master cylinder, Rear right, rear left, front right, front left. Or consult owners manual for proper bleeding.

4. Check your brake pads.

5. Check you rubber brake lines.

 

[Microrcdude]

i did multiple things to prevent this from happening. i got:

-Red-line brake fluid
-Goodridge brake lines
-New pads
-Got the master cylindar replaced

You can have a great brake system for less than $500

 

[fastezz]

i thought it might have been something as simple as bleading the brakes but it doesnt make since to me either does the master cylinder, it only happens above 70mph, but i will bleed them because the brake fluid is contaminated. thanks
Ryan

 

[Omega]

A stuck caliper that is causing the brake fluid to overheat will do the same thing. Check all the calipers to make sure they freely move in and out, replace as needed.