Suggestions
 

Recently installed a new brake booster and pedal is soft and goes near floor. The MC remained full of fluid during entire process, and I have bled 3 times. 1st question: should the engine be running while bleeding or should it be done without running, have tried both ways. 2nd question: could the proportioning valve have something to do with this? I have heard of bleeding them but unsure of the proper procedure. Any help is appreciated.

More than likely you got some air in the ABS unit. That needs a rather high end scantool to access the ABS bleeding procedure

Scan tool
 

thanks Raybz, I have access to a high end scanner if I need to, but is there a particular procedure to bleeding the ABS? Also I read you can trick the valves for the rear line into opening so you can bleed it, heard anything about that at all? Thanks again.

How do the brakes feel with the engine running after you have done the bleeding?

I remember bleeding my brakes at home (with my BF watching the level in the master cylinder to ensure we did not get air in the system) and having the pedal go to the floor and never seeming to harden up even with the bleeder valves closed. But when I started it up and vacuum was to the booster diaphragm it worked fine. No problems since.

If you did not get air into the system could there be a mechanical issue where by when you depress the brake pedal there is some sort of slack in the system?

Good Luck!

Christine

Christine
 

hey it seems to be softer as the engine is running but when it's not the booster isn't working so I believe the pedal is harder without just because of the building up of pressure with no booster behind it. If that makes any sense. It seems either way it turns up the same end result of the pedal going close to the floor, while it does stop it's just not right. I believe there is air in the ABS system somehow and am reading everything I can on it in preparation for trying to bleed it out. Ive never had to go this far into a brake job so it's a first for me, seems after I installed a new engine, every other part got jealous and wants replaced too. Way I see it the brakes aren't right now so I can't really screw em up. Fix em or break em. Either way I'll learn something. Thanks for the reply

I have only been able to do the gravity bleed method on the two Blazers I have had, using a hand vacuum pump nor the two person "press pedal,hold, open bleeder, close bleeder, pedal up" worked.

I lift the rear up a bit, start with the right rear, place a pan under right rear caliper, open bleeder, make sure master is full and then let it drip for 15 minutes. Refill master, repeat for left rear, then right front, finally left front.

Oh and I assume you bench bleed the master before installing it onto the booster right? If not, then you will never get the air out.

Never had to mess with the ABS module.

Good luck with it.

ive heard this before and I'm going to try it, curious though why lift the rear end? Seems like it would deter fluid from calipers. After that you had good brakes though. Definitely worth doing before I dig into ABS and my wallet. Thanks again

bleeding order
 

Ditto on bench bleeding the master cylinder first.

There is a proper order for bleeding the braking system, most often starting with the one furthest away from the master cylinder then doing the next closest etc.

According to my 1999 GM manual, the correct order for bleeding the system, after bleeding the master cylinder first is 1: Right Rear, 2: Left Rear, 3: Right Front, 4: Left Front

When by myself, I've used a clear bottle with a hose in it that connects to the brake bleeder valve that is partially filled with fresh brake fluid so that as the old fluid and air bubbles come out, no new air is sucked back in. In order to watch what is happening at the bottle I use an extendable (i.e. up to 8' long) broom/paint roller handle so I can push on the brake pedal from a distance.

Good Luck!

I wasn't clear
 

sorry, I'm aware of bleeding farthest to nearest I meant to ask if there was a certain way to bleed proportioning valve? Not sure if it's the same process or a certain sequence or procedure to it. First time digging this deep in brake Job, it's usually a cut and Dry process as your undoubtedly aware. Makes me feel dumb I can't figure it out. Thanks for your reply.

Oh, got it. We're good.

What year is your Blazer? I have the GM manuals for the 1999 models. I could look up what it says and scan the pages for you if you think it would help.