I have recently replaced the servo unit and rebuilt the brake calipers on my 1959 xk150 , I am now ready to bleed the system . My question is because the servo unit is vacuum assisted does the engine have to be running while bleeding the brakes? Any information would be appreciated .

Submitted by SE98-32482CJ on Sun, 04/06/2014 - 16:58

Nancy Phillip is correct. His step of running the engine is a good test on the effectiveness of the booster but if as he says you get any pockets it is likely there is an open leak. Unless the booster slave is leaking internally there is no connection to the fluid portion of the system. Best of luck!

Submitted by NE48-24099 on Sun, 04/06/2014 - 09:05

I would say....no
However, I would bleed the brakes in the normal sequence, then start the engine, pump the brakes a few times hard, turn the engine off, and bleed the brakes once again. Let us know if any air pockets came out.