When im driving in city i dont notice any problems, but when im on the highway and brake, there is good brake pressure for 3 -5 seconds, and then the pedal begins to drop slowly. Its not going to the floor but still down a significant amount.All brake cylinders appear good, andim not losing fluid. Whats the problem? Is it a simple air in the system problem?

 

Try bleeding your brakes. There may be air trapped in the system. Also check your brake fluid level. Never let it go below the MIN mark.

 

another often-overlooked solution is to snug up your ebrake cables (on my 97 they were under the center console. I snugged those up and my braking got a ton better. Since those cables were new, I have to re-adjust them to take up the extra slack from them streching out. Maybe I'll do that this weekend

at a stopling (after you've stopped) pump your brakes a few times and then hold them down firmly...see if they sink then.

 

It really sounds likea bad master cylinder. Especially if they sink whenyou pump them a couple times & hold. Classic symptom is the pedal sinking slowly & smoothly under moderate pressure.

The piston seals go bad & the fluid leaks back into the reservoir. Thats why it doesnt leak OUT.

 

+1; I agree. it probably is a master cylinder starting to go bad.

 

I just had my brake master cylinder go out about a month ago and it acted differently. However mine just went completely bad instantly instead of gradually going bad.

When you use the brake coming to a stop light or stop sign, does it feel kinda iffy whether or not the car's going to stop in time? Do the brakes not work as well as they did? Does the pedal go all the way to the floor?

 

Master Cylinder

 

my whole brake for civic needs to be replaced. After my research with brakes, i would say bleed the brake lines. If that doesnt work, then you have to check the master cylinder