Brake System Questions

[actionstan]

Hello All,

Car Saturn sl1 99 130k miles

I received some assistance here changing my brakes which went great!(thank you!) While I was down there I also "Flushed" my brake system.

The reason I am back is because after the brake job/flushing the brakes I am unable to make my wheels lock up/ABS activation happen however I am still able to stop quickly(fast enough for emergency situations)..I can get the pedal all the way to the floor without wheel lock up(but a very fast and very hard stop), and it is certainly not spongy. But I am trying to figure out If I induced Air into my system or if its just a combination of all of the new parts, at first the car had barley any stopping power at all, but I assume the more the car "adjust to the new pads" and the more the pads wear in the better it has started stopping.

Over the weekend I got brand new tires on all 4 wheels (More grip?) I put new semi metallic pads, and new rotors on the front tires, and bleed all 4 wheels.

Per Eric the Car Guys recommendation I bled the brakes by doing the Driver Front, Passenger Rear, Driver Rear, and Passenger Front, (the opposite of how most seem to do it.) I had my wife help me, I had her press the brake down, and I would quickly open the bleeder valve and close it, I had good flow from the fluid and actually got some air out, I DID NOT mess with the ABS untit, and the master cylinder never got close to low on fluid.


So, does it sound like air in the system? or just the grip of the new tires? The brakes have never been super strong on my saturn, but plenty strong to stop. Ive also read I could have damaged the master cylinder by bleeding the brakes by pumping the pedal, is this possible?

Let me know your thoughts, I may look at bleeding the brakes in the correct order, passenger rear, driver rear, passenger front, driver front. If I had air in the system would there be a dramatic difference? or is it possible that a little air will cause a little loss in stopping power?


As always, thanks!

 

[AVB]

New rotors will cause that sometimes, except the pedal shouldn't go to the floor unless the abs is activating. Could be a master cylinder problem.

 

[actionstan]

Originally Posted By: AVB
New rotors will cause that sometimes, except the pedal shouldn't go to the floor unless the abs is activating. Could be a master cylinder problem.


Hello,

Thanks! It seems like they keep getting a little better, And I have done what bedding I can, (Hard stops from high speed and keep rolling) when safe to do so. I kinda wondered if its because i'm not used to semi metallic pads, and maybe they require more bed in? Is there a way to test a master cylinder?

Thanks!

 

[Gabe]

Originally Posted By: actionstan
Ive also read I could have damaged the master cylinder by bleeding the brakes by pumping the pedal, is this possible?


That sounds like what happened.

 

[AVB]

They may get better, I never like the pedal feel with new rotors. If the pedal is going to the floor you will still need to fix that though.

 

[JHZR2]

My first thought is indeed air, like if she pulled up on the pedal without you knowing.

My second thought is that I have read that allowing the pedal to go to the floor during bleeding, when it does not usually do so during use, can indeed damage the MC. Im not so sure that I believe that, unless you have grit or something wrong with the system, but I have seen that stated, FWIW.

 

[actionstan]

Originally Posted By: JHZR2
My first thought is indeed air, like if she pulled up on the pedal without you knowing.

My second thought is that I have read that allowing the pedal to go to the floor during bleeding, when it does not usually do so during use, can indeed damage the MC. Im not so sure that I believe that, unless you have grit or something wrong with the system, but I have seen that stated, FWIW.


I used tubing and a bottle to bleed so even if she lifted up, It should have just sucked back in dirty fluid and hopfully not air.

 

[AVB]

The thing I never liked with that method is that it could suck air around the threads.

 

[actionstan]

Originally Posted By: AVB
The thing I never liked with that method is that it could suck air around the threads.


What method do you feel is best? I made sure to close the line, before my wife lifted up from the brake pedal. I went around the whole car fully, twice. Then I also went around to each bleeder without the tubing and her press down and i quickly opened the bleeders and closed them, to make sure they were pushing a steady stream of fluid. Also.. From what I am currently researching on the internet, is that if I damaged the master cylinder, it would get slowly worse.. not better. I am going to try to get a ABS activation tonight on my way home from work as long as i can find a safe place to try it.

 

[AVB]

Find a dirt, grass or gravel lot to activate the abs.

The way you bled is fine, I just don't rely on the tube and bottle to keep air from sucking in. It doesn't matter as long as you hold the pedal down. When using a vacuum bleeder I always remove the bleeders and force a cone into the port for a better seal.

I don't open then close the bleeders quickly though. I make sure the pedal is all the way to the floor before closing them, a lot of times you don't get any air out until the end of the stroke.

 

[actionstan]

Originally Posted By: AVB
Find a dirt, grass or gravel lot to activate the abs.

The way you bled is fine, I just don't rely on the tube and bottle to keep air from sucking in. It doesn't matter as long as you hold the pedal down. When using a vacuum bleeder I always remove the bleeders and force a cone into the port for a better seal.

I don't open then close the bleeders quickly though. I make sure the pedal is all the way to the floor before closing them, a lot of times you don't get any air out until the end of the stroke.


I know the car will be able to lock the wheels on dirt, gravel, or grass. I feel like it should be able to lock up on pavement too.. and its falling just short of that. I may try re-bleeding, and making sure the pedal goes all the way to the floor as you have described. I should mention, that I was never trying to get air out of the system, just exchange fluid.. I just wonder If I managed to introduce some air into the system?

Will a little air in the system cause only slightly less braking power? or does any amount of air cause a major lack of brake function?

 

[djb]

The problem here is likely the pads bedding in rather than bleeding. Did you follow the procedure of doing 10 stops from high speed in a row? Overheating the pads results in much higher wear, shaping the pads to the rotor grooves and cleaning the rotors down to bare metal. Regular braking then results in material transfer from the pads to the rotors, which is the normal low-wear operating point.

That said, take advantage of DIY. Do a mini-bleed a few days after fresh fluid or changing pads.

Micro-bubbles form when pouring fluid into the reservoir or moving the calipers back and take a day or so to rise to the top. When you have a shop do the work it's too expensive and inconvenient to have the customer come back later to get out that last air bubble. When you DIY the economics are different and you can re-bleed with little overhead.

I just bleed a tiny amount into a paper towel -- open slightly, pause a half second, close. If you got a little spot of fluid in the towel, you removed the air. Your helper should feel barely any pedal movement.

 

[Traction]

I can only suggest after learning the hard way on a older malibu and some other gm like gran prix etc. the inboard and outboard brake pads look interchangeable but if the inboard pad ends up on the outside there is a very,very short locating pin that will cause the caliper to bind and only let the inboard pad do the braking resulting in poor braking. I cooked the inside of new rotors twice by the time a figured it out. Brakes worked great after getting the pads where they were suppose to be. I still don't know if I mixed them up or whoever changed pads before did and I put them on the same.

 

[actionstan]

Originally Posted By: djb
The problem here is likely the pads bedding in rather than bleeding. Did you follow the procedure of doing 10 stops from high speed in a row? Overheating the pads results in much higher wear, shaping the pads to the rotor grooves and cleaning the rotors down to bare metal. Regular braking then results in material transfer from the pads to the rotors, which is the normal low-wear operating point.

That said, take advantage of DIY. Do a mini-bleed a few days after fresh fluid or changing pads.

Micro-bubbles form when pouring fluid into the reservoir or moving the calipers back and take a day or so to rise to the top. When you have a shop do the work it's too expensive and inconvenient to have the customer come back later to get out that last air bubble. When you DIY the economics are different and you can re-bleed with little overhead.

I just bleed a tiny amount into a paper towel -- open slightly, pause a half second, close. If you got a little spot of fluid in the towel, you removed the air. Your helper should feel barely any pedal movement.


I have done the high speed stops to the best of my ability, when its safe to do so. It has definitely gotten better, when i first put the new pads and rotors on I had almost no stopping power at first.
So i will continue to keep a eye on it.. and I may go ahead and do another bleed this weekend and follow AVB's advice on bleeding by putting the pedal all the way to the floor THEN closing the bleeder to make sure its bled thoroughly.

 

[The_Jeff]

Go read stuff specific on Delco ABS VI.

It is tough to bleed.

With you standing on the pedal with the motor running it shouldn't go more than halfway down.

 

[The_Jeff]

From the critic:

Quote:

In the past, I have used a pressure bleeder to bleed my brake system at the calipers, but I have never bled the system at the ABS control module assembly. I specifically recall that after my first brake bleed with a vacuum bleeder, the pedal got softer and has never firmed up completely despite numerous pressure bleeds. So, I'm guessing that I somehow introduced into the ABS control module during that first brake bleed.

I learned that the older Saturns used a GM Delphi VI ABS System. The main concern by wolfman and other well-respected members of this forum was that the pistons may not be in the home position after vehicle shutdown, hence the need for the scan tool to ensure a proper bleed. However, I recalled reading somewhere that older Delphi ABS systems can be properly bled without a scan tool, so I decided to do a bit more research.

Based on my research, I have learned that the scan tool is not absolutely necessary as the pistons always stay in the home position following an ABS initialization as long as no ABS activation events have occurred. In addition, based on what I've read, you will not get fluid flow from the rear calipers if the pistons are not in the home position, which is something that I have never had a problem with. However, as stated in the instructions, you must first bleed the ABS control module at the front/rear bleed screws AND at the outgoing lines BEFORE bleeding the system at the calipers. Since I have only been bleeding the system at the calipers, this may very well explain why I still have a soft pedal!

Here are the service instructions that I have found on the Delphi VI ABS system, courtesy of a textbook:

Quote:
Delphi Chassis (Delco Moraine) ABS-VI.: To bleed the ABS-VI system, the pistons in the front and rear modulators must be in their upper positions to unseat the check balls in the hydraulic circuits. GM recommends using a scan tool with bidirectional control to do this. Although a scan tool makes the job faster and easier, the pistons can be positioned manually.

To manually position the modulator pistons, start the engine and run it for 10 seconds. Verify that the ABS lamp is off and listen for several sharp clicks that indicate the pistons being driven to their upper positions. If you do not hear these distinct clicks, drive the car at 5 mph and again listen for the clicking of the ABS control motors. When you hear the clicks, carefully drive the car to the service bay without activating ABS operation.

Before bleeding the wheel brakes, attach a hose to the rear bleeder screw on the hydraulic modulator (closest to the master cylinder) and manually bleed all air from the bleeder port (Figure 9-5). Then repeat this procedure at the forward bleeder screw. After bleeding the modulator, loosen all of the brake line fittings on the outboard side of the modulator and manually bleed air from the upper ends of the brake lines (Figure 9-6).

The last stage of bleeding an ABS-VI system is to bleed the wheel brakes, either manually or with pressure equipment. Because of the variations in ABS-VI installations and because the system has been split either diagonally or front to rear on different vehicles, consult the carmaker’s service instructions for the specific wheel bleeding sequence.

 

[actionstan]

Originally Posted By: eljefino
Go read stuff specific on Delco ABS VI.

It is tough to bleed.

With you standing on the pedal with the motor running it shouldn't go more than halfway down.



being that i never ran the master cylinder dry, or messed with the abs AND had ample flow to all 4 wheels.. is it still possible i induced air into the ABS unit? If so.. I have also found this guide:

http://www.autozone.com/autozone/repairg...900c15280068379

And it seems rather helpful.. I wonder if i can rent one of those pressure bleeders..

But at this point it may be in my interest to take it to the dealer and have a full proper brake flush, I also have a coupon for Tire Discounters, but I am not sure if they have the proper equipment to really bleed/flush a brake system like this..

 

[actionstan]

UPDATE: I drove home this evening I was definitely able to cause a ABS stop on dry pavement.. So I assume i Technically have enough stopping power.. but I still may look at trying to bleed the brakes further.

Thanks all!

 

[meep]

1. if the pedal gets firm, stops, but then slowly sinks to the floor then the MC is ailing and should be replaced.

2. brake pedal should never reach the floor.

3. pedal should reach a point where it feels firm.

I've always bled from the farthest wheel from the MC, inwards. so I start with back rt and end with ft left. the reason you do this was with older systems with 'T' junctions to minimize air bubbles from taking a side-step in a T and sitting there. IDK if it's relevant as much now.

Technique. I've never had any trouble with the $7 kits with a hose and a bottle. stick it on the bleeder, pump a few times, dump bottle, refill MC, pump a few more until clear. THEN watch for 30 seconds as it gravity feeds and ensure no baby bubbles, close bleeder, move on. I turned 40 this year, and started doing this work at home around age 12.... so that's 28 years of DIY bleeding. Never needed a better tool.

You do want to make sure you get this right. Too deep of a pedal hurts reaction time in a panic situation. spongy lines will also reduce ABS effectiveness. Good luck!

 

[charbaby]

Originally Posted By: actionstan
UPDATE: I drove home this evening I was definitely able to cause a ABS stop on dry pavement.. So I assume i Technically have enough stopping power.. but I still may look at trying to bleed the brakes further.

Thanks all!


Good! It sounds like the brakes are seating nicely and your ABS is functioning properly.

Here's one thought on Pedal Bleeding/2 person bleeding:
By having a 2 person bleeding setup, the brake pedal can often extend the Master Cylinder Piston too far(further than normal braking) causing some scoring in the cylinder wall. This can lead to no pedal pressure and the replacement of the Master Clyinder. And it's not the fault of the person pressing down on the brake pedal. It just happens!

I like using either a vacuum pump or gravity bleed. Now that you've already done one good bleeding/per wheel, a gravity bleed should surfice(if you don't have a vac pump). One wheel at a time...RR, LR, RF, LF, the way you want to anyway!

I don't think that you have any air in the system but, give'er another bleed anyway!