Hi,
I have 8th gen civic with about 112k miles. regular braking works fine but once a while during sudden braking at high speed, brake pedal goes to floor and car does not stop. wheel keeps turning.
During rain it happens more often , cannot stop the car. Brake pads have been replaced along with rotor resurfaced at same time. I don't see any leaks and brake fluid level is maintained.
how to isolate, the cause ?

thanks,

 

Could be a bad master cylinder or abs pump.

 

stop driving the car and replace the master cylinder

 

The seals in your brake master cylinder piston are leaking pressure at high demand points such as emergency braking. You should have the master cylinder repaired with new seals, or replace the assembly if you wish.

do not drive the car until this repair is completed as the car is not road safe.

 

thanks all, showed it to mechanic and he suspects ABS. Going to disable ABS system and then test if braking improves , just to isolate.

 

99.9 percent chance of the master cylinder being bad and .1 percent chance of the abs modulator. This assumes no leaks.

 

After disabling ABS, brake pedal does not go to floor and is able to stop the wheels, but then car skids long distance.
On other hand, if ABS is enabled, then wheels keep rolling (you can steer) but in emergency braking, it has hard time stopping.
I have camry/Rav4/Mdx and never seen such problem with hard braking.
Other possibility may be that rear brakes don't engage effectively, thus all braking is left to front brakes. I will get that checked out.
Tires have about 40K miles but braking wasn't any different when they were new.
Any other suggestions ??

 

what would you like us to say that we haven't said yet ?

 

Took it to HONDA dealer, after test driving and brake inspection, they said it is normal, Brake system is working as it should.
Nothing wrong and no repairs needed.
Maybe I will try to get tires with better traction in wet conditions.

 

if the brake pedal goes completely to the floor beyond it's normal scope when braking hard and the car refuses to stop or slow down then there is a serious issue