question on brake bleeding with hydroboost.
Thread Starter
Safety Car
Joined: Oct 2000
Posts: 4,286
Likes: 172
From: Lake Wylie, South Carolina
question on brake bleeding with hydroboost.
I just finshed installing brand new SS hard lines and braided flex lines. I have a completely dry system right now and have a couple questions that I couldn't answer from the search function.
1. If I have the MC cap off and both front and rear resevoirs full and then push in the pedal should the fluid squirt out the top? The reason I ask is that I have done this and I am seeing some bubbles but no force full expulsion of fluid. I am trying to make sure that the push rod is long enough from the HB to the piston of the MC. The MC is a new unit with the shallow piston cup from the late '70's models not the deeper piston cup that came on the earlier models.
2. If I am ok from the first question what should I do first to bleed a dry system? Open all the bleeder screws?
3. As I said before I have the MC full and have pumped the brakes with the cover fastened to the MC but the fluid level does not go down. Is this because of the amount of air in the lines or could this be another indication of the HB units rod not fully activating the MC piston.
4. Lastly, I do not have the HB fluid lines hooked up to the pump but I do have the fittings capped. I can bleed the brakes without the HB hydraulic lines being hooked up correct?
Thanks
1. If I have the MC cap off and both front and rear resevoirs full and then push in the pedal should the fluid squirt out the top? The reason I ask is that I have done this and I am seeing some bubbles but no force full expulsion of fluid. I am trying to make sure that the push rod is long enough from the HB to the piston of the MC. The MC is a new unit with the shallow piston cup from the late '70's models not the deeper piston cup that came on the earlier models.
2. If I am ok from the first question what should I do first to bleed a dry system? Open all the bleeder screws?
3. As I said before I have the MC full and have pumped the brakes with the cover fastened to the MC but the fluid level does not go down. Is this because of the amount of air in the lines or could this be another indication of the HB units rod not fully activating the MC piston.
4. Lastly, I do not have the HB fluid lines hooked up to the pump but I do have the fittings capped. I can bleed the brakes without the HB hydraulic lines being hooked up correct?
Thanks
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Yes to number 1.. When you push the pedal if you don't have a cover plate on the fluid always squirts up and you make a mess.
You could open all bleeders and wait for gravity to work. They always recommend bench bleeding the master cylinder but gravity should do the job over time.
I had my hydro boost off this weekend and my hole in the back piston for the master cylinder is only about 3/8th inch deep, no more??
You don't need the hydroboost pressure lines hooked up since the rod goes straight through no power assist is needed to bleed the system.
I always pressure bleed my system. Using a old cap I have a air connection welded to the cap. I then use shop air turned down to about 10 pounds and bleed the system that way.
Good luck . I can't see just pumping the pedal with the bleeder screws open working.
You could open all bleeders and wait for gravity to work. They always recommend bench bleeding the master cylinder but gravity should do the job over time.
I had my hydro boost off this weekend and my hole in the back piston for the master cylinder is only about 3/8th inch deep, no more??
You don't need the hydroboost pressure lines hooked up since the rod goes straight through no power assist is needed to bleed the system.
I always pressure bleed my system. Using a old cap I have a air connection welded to the cap. I then use shop air turned down to about 10 pounds and bleed the system that way.
Good luck . I can't see just pumping the pedal with the bleeder screws open working.
Thread Starter
Safety Car
Joined: Oct 2000
Posts: 4,286
Likes: 172
From: Lake Wylie, South Carolina
Norval,
Do you remember the length of your push rod? If it is still out could you measure it for me?
When I pump the pedal with the cover off I get a few bubbles but make no mess so that tells me that the piston is not engaging enough. I do have the shallow cupped MC that like you said is no more that 3/8 deep if that. I used the rod that came with the HB. I still have my old rod so I would think I could just cut it down and smooth out the end and re use it. Agree?
There is no difference in which end of the rod goes into the HB and which end contacts the MC piston is there?
Thanks!
Wade
Do you remember the length of your push rod? If it is still out could you measure it for me?
When I pump the pedal with the cover off I get a few bubbles but make no mess so that tells me that the piston is not engaging enough. I do have the shallow cupped MC that like you said is no more that 3/8 deep if that. I used the rod that came with the HB. I still have my old rod so I would think I could just cut it down and smooth out the end and re use it. Agree?
There is no difference in which end of the rod goes into the HB and which end contacts the MC piston is there?
Thanks!
Wade
