If you ever replace a brake master cylinder on a late model (2006-2012) Chevrolet Impala, get ready for some fun attempting to bleed the lines. The master cylinder sits below the BPMV and the lines rise upward from the master into flexible tubing and they run downward into the BPMV. Trying to bleed air from these lines is a very difficult job.

G.M. has a PIC5468A regarding this problem. They suggest that you loosen the lines at the master and rotate them downwards at the master before bleeding. Don't bother. The lines will still rise above the master at the point they fasten to the BPMV. I have seen techs spend hours trying to bleed these lines. I saw one tech unbolt the master with lines attached and suspend it over the engine with a bungee cord and use a pressure bleeder. Didn't work.

The only thing I found that will work is to first bleed the lines manually at the BPMV. Then I use an adapter from the brake flush machine to my mightyvac. I pump up 25 in. of vacuum and let it sit for 10 minutes then I pump the pedal slowly 30 or 40 times. Note - you will have NO brake pedal doing this due to the vacuum and the pedal will go easily to the floor. Repeat this procedure 3 or 4 times as necessary and it has always worked for me.

James from Florida