Replaced Bendix ABS w/ '96 setup - low pedal now

Bendix system was shot. Took both feet as hard as I could push to get this thing to slow down. I ripped it all out and replaced w/ a '96 booster and master cylinder from AutoZone and a prop. valve from a yard. Brake lines are solid, bled the brakes properly, so there isn't any air in the system and I'm not seeing any leaks. So, a few questions:

1) Does the vacuum hose connect to the side of the manifold? That was the only approx. diameter connector that was capped on mine.

2) Would bad pads/rotors cause the low pedal? I noticed while doing the job that the front brakes are beyond shot. The driver's is paper thin and there are two gouges carved into the rotor about 1/2" wide and 1/16" deep. Guy I bought it from was really bad at maintenence from what I've found so far - not good for me...

So, needless to say, this weekend I'm doing the front brakes. What else should I do while I'm in there? I also can only assume the rear brakes are probably bad too, but didn't really look b/c he told me the cylinders were new, so I assumed why replace the cylinders and not do a whole job? I'm also not familiar w/ drum brakes - always steered away b/c I was told they're such a PITA to do....is this true? Am I better off just letting a shop do the rear?

Did you bleed the master?

Slo-Sho said:

Did you bleed the master?

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Yeah, but not completely confident on my job. I had it level and was doing slow strokes w/ 10 seconds in between as recommended in the instructions. I must have done this for 10 minutes, but for some reason, there were still a few bubbles in the front hose that I couldn't get rid of. Out of frustration I just said F* it and installed it, but I thought for sure that either the bubbles would get pushed out during the system bleed or that they'd just come to the top of the master. Was I flawed in my thinking?

You noted it has or had ABS, you do realize those require special equipment to bleed the ABS unit? If it no longer has the ABS, then disregard what I just said.

Jeff

If the pedal feels firm but low I'd suspect that rear brake shoes are too far away from drums. For test purposes you could adjust the shoes as close to drum as you can get. Then pedal shouldn't move much. Remember to roll back the adjustment couple of notches before hitting on the road.

But if it feels spongy then you have some air in system. I assume you took out the hole ABS master cylinder setup with modulator so there is no more ABS specific bleeding rituals to do.

-Kimmo-

Correct, no ABS system at all.

With the vehicle off, the pedal is hard as hell which is correct b/c it doesn't have assist. It moves only an inch or two.

With the vehicle running, it is soft, but engages only an inch or two off the floor. Like I said, I'm thinking it might be b/c the front brakes are completely shot and who knows, the rears might be too. Guess I'll just change out the fronts this weekend and see if it improves. If not, then I'll just have to assume that there is air in the system somewhere and do the whole bleeding process again.

Disk brake pads don't return from braking position to normal position like drum brake linings do. This is the reason I'd go to check rear brakes first. You should be actually able to hear those brake shoes move when you push the pedal.

But it is definitely a good idea to replace all worn brake parts while you are at it.

-Kimmo-

I have gotten serveral bad master cylinders from AutoZone. Don't drive yourself crazy if you can find the problem. Change all pads and ensure the calipers and cylinders and in working order and if after a GOOD bleed job is done, you still have the problem, remove the mc and return it---then start over and make sure you bench bleed well.

Thanks for the help - didn't know that calipers didn't return. Guess I'm changing front and rear then.

Regarding the brake bleeding, if there were some air in the MC, wouldn't that have been forced out during bleeding the calipers/cylinders? I went through 2 large bottles of brake fluid doing this and I know that I pushed fresh fluid through b/c the old fluid was brown whereas the new stuff was clear, so I made sure to bleed till a lot of clear came through.

Sounds like there is still air in the master. Have a helper rapidly pump the brake pedal 20 times and HOLD. Place a rag under one of the two brake lines coming from the master to the prop valve. Slowly loosen one of the fittings on the prop valve and bleed from there. Crack open the fitting about 5 times then move to the second line and repeat. Don't forget to bleed all 4 wheels after you have bled the master.

Okay, so pump 20 times and hold. I loosen one hose, fluid will spew out and then I tighten and the pumper releases? I do this whole process for 4 more times and then switch to the other hose for 5 times?

Just didn't know if by 5 times you meant actually "5 sets" or just 5 turns of the fitting to loosen it enough? Seems easy either way, but just don't want to make someone pump an extra 160 times if not needed!!! :spin1:

If the MC is not level when you bleed the brakes, air in the MC will stay trapped. That is why you should bench bleed the MC first, to insure it's level and to insure no more bubbles; bubbles=air still in there.

gone postal said:

Okay, so pump 20 times and hold. I loosen one hose, fluid will spew out and then I tighten and the pumper releases? I do this whole process for 4 more times and then switch to the other hose for 5 times?

Just didn't know if by 5 times you meant actually "5 sets" or just 5 turns of the fitting to loosen it enough? Seems easy either way, but just don't want to make someone pump an extra 160 times if not needed!!! :spin1:

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Yes, 5 cycles for each of the two outlets on the master. You will know when there is no more air in the master. Don't forget to bleed all 4 wheels following this, I know it's a PITA but you gotta do it right.

DON't pump the hell out of them, apply slow steady pressure while opening the bleeder,just before the pedal bottoms out, close the bleeder, repeat 'til fluid no longer has air bubbles.
Pumping the pedal only serves to put any air in there through out the system and can ruin the MC.
As for the MC you should bleed it much like you were bench bleeding it, except the pedal is taking the place of manually moving the piston..
Search in here for the proper procedure.
What I do if the MC is on the vehicle is to take two pieces of tubing( we already have these made up, they come in handy) with fittings to fit the MC we are doing, these lines are only about 2" long, attach one end of clear tubing to theses "nipples" and place in the other end in the MC, fill the MC, slowly... push the pedal down, repeat 'til you do not see air bubbles

There are directions for making a pressure bleeder here and elsewhere. you would be wise to pressure bleed the system. This will force all the air out. The rest of the gang is right, soft pedal is usually a problem in the rear. I did this swap on my old jeep and had the same problem. I made the pressure bleeder for about $20 (you can buy them for $60 or so) and doing it myself it took about 30 minutes to get the whole system bled. After that I had better brakes than I ever did. If you google for a pressure brake bleeder you should find a site with directions, it's on some guys bmw site.

Well if pedal feels hard without boost I'd say that there is no air in the system. Just check those worn brake parts.

-Kimmo-

dizzymac said:

DON't pump the hell out of them, apply slow steady pressure while opening the bleeder,just before the pedal bottoms out, close the bleeder, repeat 'til fluid no longer has air bubbles.
Pumping the pedal only serves to put any air in there through out the system and can ruin the MC.
As for the MC you should bleed it much like you were bench bleeding it, except the pedal is taking the place of manually moving the piston..
Search in here for the proper procedure.
What I do if the MC is on the vehicle is to take two pieces of tubing( we already have these made up, they come in handy) with fittings to fit the MC we are doing, these lines are only about 2" long, attach one end of clear tubing to theses "nipples" and place in the other end in the MC, fill the MC, slowly... push the pedal down, repeat 'til you do not see air bubbles

Click to expand...

DAMN!!!! And to think that the MC came w/ 2 nipples and tubing for the purpose of bleeding it and I threw them away after i did the bench bleeding. I'm sure I can fab something up or maybe I'll look into this pressure bleeding thing.

Yes, the pedal is hard when not running - moves maybe an inch or two - not much. I honestly think it's the brakes themselves b/c the front brake pads are literally just a few sheets of paper thick and I don't know rear brakes and didn't really even look, but if the front is that bad, then I'm sure the rear is shot too. I'll look into manually moving the adjusters too - maybe they froze up?!?

I'll bet if you replace the pads and rear shoes along with the rear hardware you will get a much better pedal. With pads that bad all the bleeding in the world will not fix the problem.
Note of caution: if you replace the rear shoes, check the e-brake cables for tightness, if they are lose against backing plate you will want to adjust the e-brake. Nothing will get your attention faster than a rusty e-brake cable coming lose from the rear shoes and backing plate and being driven over. That sudden jerk and bang will have you checking your "undies'.

Well, I replaced the front pads & rotors - the driver's side was down to the metal!!! I also bled the master and got a few bubbles out and then all of the lines and the system is better, but still doesn't seem near as powerful as my '07 Passat or being able to lock up the 31's at highway speed as I've seen others suggest.

I looked at the pass. rear and the shoes are fine. The self-adjusting thing doesn't appear to be working though - heard this is common. Will the brakes still move to the proper spot and stay if the self adjuster isn't working? So, if I tighten it by hand, how far do I go? I read that w/ the drum on, you tighten until you hear the shoes rubbing (when you turn by hand) and then back off a lil. I tried this, but it sounds like they're rubbing when only 2 turns out. If that sounds about right, then fine, but I just don't want to have them rubbing constantly and then prematurely wear out.

I tightened the rear shoes as much I could. then pressed brake pedal and pulled emergency brake few times to settle the shoes in correct position. And tightened more repeating this until wheel couldn't be turned by hand. Then I untightened shoes about 5 notches (not turns ) now the wheels should be loose enough to be turned by hand. Probably you can feel shoes contacting a little bit the drum but it is okay. They'll wear quite fast to new shape.

-Kimmo-