Hey guys , I have been floating around the forum and have found many interesting threads, but not one with my particular issue. I had to replace the 2 rear lines behind the ABS block. DONE. Bled according to spec RL, FR, RR, FL. Here is my problem. I have no air coming out of the RL or FR. However the RR and FL are a different story. I got the RR to have a trickle of tiny bubbles, but the FL CONSTANT air flow. Like as if some little goblin was hiding with an air hose and blowing air into my FL line. I mean NON STOP bubbles some times frothy like a foam. I bled this thing 4 different times drove the thing for 30 min or so and the brakes got soft. I spent and hour on just the FL today alone.... In my 20 years or working on cars and many other mechanical things I never ran across something so bizarre... ANYONE any ideas?
Could the MC have a bad seal and be blowing air into the lines?
And No I never let the MC run dry.

Thanks

 

Not even ONE reply thats crazy

 

OK, I'll take a stab. Yes, I think it could be the master cylinder. The first clue is that you have a problem with diagonally opposite wheels. I'm 99% sure the two sections of the dual master feed diagonally opposite wheels.

If it has the original MC, what can happen is that parts of the MC bore that never got touched in normal driving get a bit corroded. Now when you start bleeding the brakes you are making seals go outside of their normal range and perhaps over those areas that might be rough and compromise an already weak seal. I'll bet the problem is on the rear section of the MC as that one can pull in air. There is no way for the front section to pull in air other than through the rear section.

I'd replace the MC.

Dave

 

How exactly did you bleed the brakes???

Did you pump the pedal 3 times then hold, and open the brake bleeder nut on each caliper at each wheel ?

Or did you use the gravity method ??

Chances are if you've been doing it for 20 years you did it right, but it's strange that you would still get air in the system unless as has been mentioned the MC is bad.

 

I did both. Weather has been crappy so I haven't gotten to the MC but that will be my next job. I just figure if I have air getting in somewhere then there must be fluid coming out if the same place... but I have no fluid anywhere. unless it's leaking into the brake booster... Hummmm???

 

Thanks Dave..... MC will be my next step