Join Date: Apr 2004
Location: Whitby, Ontario
1st question - when you bleed the brakes, does air come out - ie: bubbles in the expelled fluid?
If so, then you have air entering the system somewhere, as obviously, that should not happen. If not, then you are not technically bleeding the system, and the problem is something else, that is sort of "repaired" by the pedal moving its full travel during the process.
That would tend to indicate the master cylinder is faulty, since no other parts are activated at that time.
Next issue, the ABS pump would not have a bearing on the braking system, since it is a pressure routing system only, and related to what the control unit tells it. Even if it fails, the system defaults to "normal" braking. The dealership can tell what is happening with the ABS with a DRBIII, and can activate all the valves and pump to determine if it is working correctly, and can tell if there are any faults in the controller that would have activated the system and caused a failure.
Basically, tere is nothing in the ABS portion of the system that can cause hydraulic pressure failure.
The only system parts that can cause that, are the master or wheel cylinders, and the physical brake lines.
So the first thing to check is the master cylinder.
place your foot on the brake pedal very lightly, with barely and weight or pressure.
The pedal should remain solid, and not move, even over a period of time, say 1 or 2 mins.
If it even slightly moves, the master cylinder has an internal leak, and should be replaced. You may need to try this several times, and at various brake pressures: press the brakes hard, to about 1/2 way, then keeping the pedal there, gently release the foot pressure, and see if the pedal drops. Try this in several spots in the travel.
The reason, is that there may be a bad spot in the cylinder bore, and you don't always press the pedal to that exact spot every time.
If you can press the pedal hard and maintain a hard pressure, but the pedal slowly goes down, and you tend to have a slight fluid loss over time, then you need to look for a leak in the rest of the system, such as rusted lines under the body, You only need a very tiny pin-hole to allow fluid to seep out, and possibly suck air in to have the failure of the brake circuit. Again, the question #1 is important, by looking at which wheel bleeder if any is showing bubbles. That narrows it to that line or wheel cylinder.
First places to start anyway.
goal - have one of my parts on every DI car:biggrinfl
Honoured to be January 2007 COTM.THANK YOU ALL.