ABS and master cylinder replacement

[antoniobanderas]

well,Started having a question about the pedal feel in my grand am,so ,i bleed the modulator,the wheel cylinders and front brakes, still ,not much of a difference,so i decided I had to have a bad master cylinder,i got me a new one ,proceeded with the separation of the master from the modulator ,more or less,I managed to put all back together, it seemed to work better but not quite,there was always a delay in the braking force to the car,I then decided to put a new brake booster thinking that could be it,well,now the pedal goes almost to the floor before it applies braking action,I suspect that, when I disassembled the master cylinder from the modulator,i disturbed the internal gears tension in the modulator,,if this the case,can someone tell me something about how to restore my braking system? does it requires special tools? or what the car is a grand am 1993 v6 3.3

[rixGAphx]

I understand that when the ABS module is separated from the MC, there is a very special bleeding operation that must occur.
I don't know what it is.

Also, the MC itself should be 'bench'bled' before installation.
Whenthe MC is installed, it is impossible to bleed all the air out, 'cuz the small amount of remaining air rises above the exit ports.
When you 'bench bleed', you kinda twirl the MC (while injecting brake fluid) so the trapped air can escape.

You can NEVER remove the trapped air, from the MC or the Module, by conventional bleeding at the wheels.
* * *

One of the main causes of lousy brake performance in older vehicles is the 'Combination Valve'.
This is a very important part of brake systems, especially like yours (and mine) with front disks and rear drums.
For an explanation of this valve, see http://auto.howstuffworks.com/master-brake2.htm

Your problem may be with this device, and have nothing to do with ABS, MC, or booster.
* * *
At this point, you have probbly gotten yourself so deep in trouble that a professional needs to sort it out. $$$.

Sorry,
-Rick

[antoniobanderas]

hi ,i think that abs doesnt have a combination valve or proportioning valve ,hence the abs sistem thanks for your replay

[antoniobanderas]

UPDATE . today,I went to a junk yard and got me the entire ABS assembly for 80 bucks ,installed and then bleed it as per the Haynes manual, brakes were terrible! worst than before,,sooo I WENT to my mechanic and explained to him the story,he then started the car up and proceeded to bleed the 4 brake lines attached to the ABS assembly, then ,he did the same with the rear and front wheels ,after that ,guess what? car has a brakes again! so much as per the bleeding instructions in the Haynes manual! i always thought the brakes had to be bleed different ,especially with ABS,it turns out its no so ! he did it just like a conventional way,you pump the brakes like crazy for 5 0r 6 times ,hold the pedal, purge,close bleeder,and repeat two or more times in each wheel belive it or not ,this is how he did it and got a firm pedal which I could not get with the other method,
my method was to crack open the bleeder ,then push the pedal in ,hold it down ,then close bleeder and so forth,at each wheel,this did not work! also,at the ABS,modulator/master cylinder same thing,with no results,only until he did it the conventional way ,he restored the firmness to the brakes ,go figure! anyways,I am glad whichever way as long as I have brakes again

[rixGAphx]

Originally posted by antoniobanderas
UPDATE .....

... My method was to crack open the bleeder, then push the pedal in, hold it down, then close bleeder and so forth; repeat at each wheel.

This did not work!
No, this will never work.
You didn't get this method from Haynes.

NEVER open the bleeder screw unless there is pressure on the pedal.
If you open it without pressure on the pedal, a little fluid will flow out and a little air will flow in. So each time you do that, you are losing fluid and letting more air in.

Proper bleeding is definitely a 2-person job, unless you have a 'bleeder kit' (hoses and a bottle of extra fluid).

Glad you're back on the road, and your brakes are good enough for me to drive in front of you!! :D :D
-Rick

[antoniobanderas]

I could scan the haynes page were it says so and you will see i am telling the true ,they claim the ABS are different systems and SHOULD BE BLEED LIKE I EXPLAINED I belived it and the rest is history

[eaglesrealm]

The ABS does not have to be bled differently (typically in most systems) AS LONG AS it does not cycle.

With an ABS, there is a normal off state that directs the flow from the master cylinder through the ABS and out to the brakes. Even if you get air in there, you can do the traditional bleeding method until it is out. When you changed the ABS itself, that only worked because the areas of the modulator that act only during ABS events was already filled with fluid. If you had put that on and not bled the brakes right, leaving air in the system and did an ABS stop, some of that air could have made it into the other 1/2 of the ABS and you would then leave yourself with more fun!!!

All in all, if you have air at all in the other part of the ABS unit, you typically need a special tool to plug into the car so you can cycle the unit while parked so you can push the fluid back through those modulator circuits and get the air out. That is in the Haynes manual.

Hopefully that made sense.

[antoniobanderas]

I must have a Haynes manual from the old days ,all it says in mine is crappy and erroneous

[antoniobanderas]

so,are you saying that unless i don't make a panic stop,abs stop,that is, the brakes would work good even if i had air in the modulator but not in the master cylinder and lines?,as long as i don't get the modulator activated the brakes would work good,, hmm ,i don't think so,i believe the brake fluid goes trough the modulator at all times ,but will only activate,if the wheel sensors tell it to,unless there is a bypass circuit inside the modulator itself, but the way i see it ,from the master cylinder goes directly to the modulator and then to the wheels

[rixGAphx]

Originally posted by antoniobanderas
[ from first post ]:My method was to crack open the bleeder, then push the pedal in, hold it down, then close bleeder and so forth; repeat at each wheel.

....I could scan the Haynes page were it says so and you will see I am telling the truth....
CORRECT method:
1. Push the pedal in and hold it down,
2. THEN crack open the bleeder and bleed,
3. Then close bleeder.
4. Repeat until fluid runs clear and free of air.
5. Repeat at each wheel.

I repeat: Do NOT crack open the bleeder screw first!!!
Push on the brake pedal first, THEN open the bleeder.

Go ahead and scan the Haynes page that says 'open bleeder before pushing the pedal'; if Haynes ever wrote that, they would and should be sued.

The above procedure only applies to bleeding the 'corners', like when you change calipers or wheel cylinders.
It is the same regardless of ABS or not.

Hope this helps.
-Rick

[antoniobanderas]

9-18
Chapter 9 Brakes WATCH STEP 18 !! you will see it there




9 Brake system bleeding
Warning: Wear eye protection whenever bleeding the brake system, if the fluid comes in contact with your eyes, immediately rinse them with water and seek a physician's advice.
Note: Bleeding the hydraulic system is necessary to remove any air in the system or when the system has been opened for repairs.
1 It will probably be necessary to bleed the system at an four brakes if air has entered the system due to low fluid level
2 If a brake line was disconnected only at a wheel, then only that caliper or wheel cylinder must be Wed unless the system is allowed to drain through the open line..
3 If a brake line is disconnected at a fitting located between the master cylinder and any of the brakes, the part of the system served by the disconnected line must be bled.
4 Remove the master cylinder reservoir cover and fill the reservoir with brake fluid. Reinstall the cover. Note: Check the fluid level often during the bleeding operation and add fluid as necessary to prevent the fluid level from falling low enough to allow air bubbles into the master cylinder.
5 Have an assistant on hand, as wen as a supply of new brake fluid, an empty clear plastic container, a length of 3/16-inch plastic, rubber or vinyl tubing to fit over the bleeder valve and a wrench to open and close the bleeder valve.
Conventional (non-ABS) system
Refer to illustration 9.8 *
6 Remove any residual vacuum from the brake power booster by applying the brake several times with the engine off.
7 Beginning at the right rear wheel, loosen the bleeder valve slightly, then tighten it to a point where it is snug but can still be loosened quickly and easily
8 Place one end of the tubing over the bleeder valve and submerge the other end in brake fluid in the container (see Mustration)
9 Have the assistant pump the brakes slowly a few times to get pressure in the system, then hold the pedal firmly depressed.
10 While the pedal is held depressed, open the bleeder valve just enough to allow a flow of fluid to leave the valve. Watch for air bubbles to exit the submerged end of the tube. When the fluid flow slows after a couple of seconds, close the valve and have your assistant relaase the pedal.
11 Repeat Steps 9 and 10 until no more air is seen leafing the tube, then tighten the bleeder valve and proceed to the left rear wheel, the right front wheel and the left front wheel, in that order, and perform the same procedure. Be sure to check the fluid in the master cylinder reservoir frequently.
12 Never use old brake fluid. It contains moisture that wii deteriorate the brake system components.
13 Refill the master cylinder with fluid at the end of the operation.
14 Check the operation of the brakes. The pedal should feel solid when depressed, with no spongmess If necessary, repeat the entire process. Warning: Do not operate the vehicle if you are in doubt about the effectiveness of the brake system.
Anti-lock Brake System (ABS)
Warning: To properly bleed the ABS system on these vehicles, this entire bleeding procedure must be followed. This method can only be used if the ABS warning lamp is not illuminated and the ABS control system is functioning property. Do not press on the brake pedal during this procedure unless you are directed to do so.
15 With your foot off the brake pedal, start the engine and run it for at least 10 seconds while observing the ABS warning lamp. The warning lamp should light for approximately three seconds and then go off.
16 Repeal Step 15. If the warning lamp fails to come on at al or if it stays on after 10 seconds, this procedure must be stopped and the ABS system must be diagnosed and repaired before bleeding. If the warning lamp comes on for approximately three seconds and then goes off, proceed to Step 17.

9.8 When bleeding the brakes, a hose is connected to the bleeder
valve at the caliper (or wheel
cylinder) and then submerged In
brake fluid. Air willbe seen as
bubbles in the container or in the
tube. All air must be expelled before continuing to the next wheel
Note: The ABS modulator valve is mounted on the side of the master cylinder. There are two bleeder valves on the front of the ABS modulator valve assembly. The innermost bleeder, closest to the fluid reservoir, is referred to as the rear bleeder. The outermost bleeder it referred to as the front bleeder. Check the fluid reservoir throughout this procedure and make sure it is kept filled to the proper level.
17 Repeat Step 15 five times to correctly position the pistons in the modulator valve. Place one end of a clear hose onto the rear bleeder of the ABS modulator. Place the other end into a partially filled container of clean brake fluid.
18 Open the rear bleeder 3/4 of a turn. Have an assistant press down the brake pedal and hold it until brake fluid begins to flow into the tube. Close the bleeder and slowly release the brake pedal. Repeat this procedure until no air bubbles are visible in the hose or the container when the pedal is pressed down.
19 Repeat Steps 17 and 18 on the front bleeder of ABS modulator.
20 Beginning at the right rear wheel, loosen the bleeder valve slightly, and then tighten it to a point that it is snug but can be loosened easily.
21 Place one end of a clear hose onto the bleeder and the other end into a partially filled container of clean brake fluid (see •illustration 9.8).
22 Open the bleeder valve and have the assistant slowly press down on the brake pedal dose the bleeder and slowly release the pedal.
23 Wait at least five seconds and repeat Step 22.
24 Repeat Steps 22 and 23 until no air bubbles are present m the hose or the container when the pedal is pressed down. Tighten the bleeder valve.
25 Repeat Steps 20 through 24 on the left rear wheel, the right front wheel and the left front wheel, m that order. Be sure to check the fluid level in the master cylinder reservoir frequently.
26 Place one end of a clear bleeder hose onto the rear bleeder of the ABS modulator. Place the other end into a partially filled container of clean brake fluid.
27 Have the assistant press down on the brake pedal with moderate force and slowly open the rear bleeder 3/4 of a turn to release pressure. Close the bleeder and have the assistant slowly release the brake pedal.
28 Wait five seconds and repeat Step 27 until no air bubbles are present m the hose or the container when the pedal is pressed down. Tighten the bleeder valve.
29 Repeat Steps 27 and 28 on the front bleeder of ABS modulator. Top up the master cylinder fluid reservoir.
30 Turn the ignition switch on and appry moderate pressure to the brake pedal. The pedal travel should not be excessive and the pedal should feel firm. If not, proceed to Step 32.
31 Start the engine and apply moderate pressure to the brake pedal. If the pedal travel is not excessive and the pedal feats firm, proceed to Step 33.
32 If the pedal feels soft or has excessive travel, repeat the entire

[rixGAphx]

Originally posted by antoniobanderas
WATCH STEP 18 !! You will see it there:

9 Brake system bleeding
9.8 When bleeding the brakes, a hose is connected to the bleeder
valve at the caliper (or wheel cylinder) and then submerged In
brake fluid.
Air will be seen as bubbles in the container or in the tube.
All air must be expelled before continuing to the next wheel
Note: The ABS modulator valve is mounted on the side of the master cylinder. There are two bleeder valves on the front of the ABS modulator valve assembly. The innermost bleeder, closest to the fluid reservoir, is referred to as the rear bleeder. The outermost bleeder it referred to as the front bleeder. Check the fluid reservoir throughout this procedure and make sure it is kept filled to the proper level.
............
17 Repeat Step 15 five times to correctly position the pistons in the modulator valve. Place one end of a clear hose onto the rear bleeder of the ABS modulator. Place the other end into a partially filled container of clean brake fluid.
18 Open the rear bleeder 3/4 of a turn. Have an assistant press down the brake pedal and hold it until brake fluid begins to flow into the tube. Close the bleeder and slowly release the brake pedal. Repeat this procedure until no air bubbles are visible in the hose or the container when the pedal is pressed down.
Yes, it says that.

But, that procedure is based on the use of a 'bleeder kit' (bottle of fluid and a tube from the bleeder screw into the fluid):

"5 Have an assistant on hand, as well as a supply of new brake fluid, an empty clear plastic container, a length of 3/16-inch plastic, rubber or vinyl tubing to fit over the bleeder valve and a wrench to open and close the bleeder valve.
Conventional (non-ABS) system:
Refer to illustration 9.8
6 Remove any residual vacuum from the brake power booster by applying the brake several times with the engine off.
7 Beginning at the right rear wheel, loosen the bleeder valve slightly, then tighten it to a point where it is snug but can still be loosened quickly and easily
8 Place one end of the tubing over the bleeder valve and submerge the other end in brake fluid in the container (see illustration)
9 Have the assistant pump the brakes slowly a few times to get pressure in the system, then hold the pedal firmly depressed.
10 While the pedal is held depressed, open the bleeder valve just enough to allow a flow of fluid to leave the valve. Watch for air bubbles to exit the submerged end of the tube."
* * * *
My first post said:
"Proper bleeding is definitely a 2-person job, unless you have a 'bleeder kit' (hoses and a bottle of extra fluid)."

The procedure which you quoted from the Haynes manual is a very safe way of doing a two-man job, and specifies the use of the 'bleeder kit'.
I agree, that if the tube is connected to the bleeder and the end is in a bottle of fluid, then it is perfectly OK to open the bleeder screw first.

I only use the bleeder kit when doing the job myself, not if I have an assistant.
My reference ("NEVER open the bleeder screw unless there is pressure on the pedal.") was to you bleeding the brakes with an assistant, but without using a bleeder kit.
Your post didn't mention using a bleeder kit.

Did you use a bleeder kit?
If so, my apologies. You are absolutely correct.

Peace,
-Rick

[antoniobanderas]

OK,whatever,,the point is this method is Worth shit,it will not work,just use the conventional way and IT WILL WORK,note;always while bleeding have the engine on running you will be ok,why?the internal modulator ports will stay open and allow the bleeding,remember,the car is not moving. peace