invisible_squid

I had this happen to me. The first time it happened was immediately after an ABS event. The pedal would go almost fully to the floor, except it would build pressure and actually brake near the bottom of the travel. Felt almost like the master cylinder was bypassing until the very last minute. Took it to a local dealer, who first diagnosed it as a faulty brake booster. Which does not make sense at all. If the booster was failing, the brakes would be harder, and I would see the revs jump up from the vacuum leak, and I was getting none of that. I told them to test and check the HCU because a tech I was friends with said it sounded familiar. In the end, what was happening was that the ABS HCU bypass valve was stuck open, allowing pressure to flow into and fill the accumulator before the system gained any pressure. When they replaced mine, they didn't bleed it properly, so the system was still full of air, making it seem like the problem was still there. They forced me into giving them authorization to change out the booster, too, which would mean they'd have to bleed the system twice. Haven't had any issues since