Bleeding the air out of the ABS

[Annatar]

As some of you might or might not remember, I broke off a baked-in bleeder valve on one of my brake callipers. Trying to extract it with a tap, the tap broke, so I ended up having to completely remove the driver side front brake calliper and have the bleeder valve extracted at a machine shop.

I've since spent 2 L of brake fluid trying to bleed the brakes to no avail: the brake pedal falls through to the firewall and the brakes are very weak, which leads me to believe that the air got into the ABS (as the brake line had been disconnected for almost two weeks and I couldn't clamp it).

I can hear the piston in the master cylinder slamming against the cylinder housing.

So now the question is, is there a way to short-circuit a fuse, or some other way to pulse the ABS system to get the air out of it other than driving the vehicle and trying to get the ABS to engage, as I basically have no brakes?

If there isn't, which scanning tool do yinz recommend specifically for our ZL1's which has the ABS bleeding functionality?

[Camaro__ss]

Here’s what I did when my brake hose broke. You need a pressurized bleeding system such as Motive tat attaches to master cylinder. Make sure the reservoir is full, pump the pressurizer up to like 30 psi or so. It should hold pressure. Bleed the brakes starting with the wheel furthest from the master cylinder. As long as your master cylinder reservoir didn’t drain dry there should not be air in the abs.
If you did somehow entrain air in the abs, you still need a pressurized bleeding system. I think you also need a diagnostic scan tool that can activities the abs pump as you are bleeding. I have not done that before, so I don’t know if that is the exact procedure. The scan tools that do that sort of thing are not the cheap ones-you need the pro level one.

[ZMEnow]

Originally Posted by Camaro__ss

Here’s what I did when my brake hose broke. You need a pressurized bleeding system such as Motive tat attaches to master cylinder. Make sure the reservoir is full, pump the pressurizer up to like 30 psi or so. It should hold pressure. Bleed the brakes starting with the wheel furthest from the master cylinder. As long as your master cylinder reservoir didn’t drain dry there should not be air in the abs.
If you did somehow entrain air in the abs, you still need a pressurized bleeding system. I think you also need a diagnostic scan tool that can activities the abs pump as you are bleeding. I have not done that before, so I don’t know if that is the exact procedure. The scan tools that do that sort of thing are not the cheap ones-you need the pro level one.

Yes an active scan tool will turn the abs pumps on but they are not cheap. I have a lift so I first do the inners in the spec’d order, then I start the car put it in gear at just idle and that will pulse the abs. I then do the outers in the spec’d order, restart, idle, and then hit the clutch, done.

[ariZona28]

You probably already know but I'll throw it out for you just in case, don't forget the non-traditional sequence of RR, LF, LR, RF. Currently on pg 30 in the Z/28 section there's a thread pertaining to this. I'm pretty sure the ZL1 is the same.

[rednecks70]

I've only worked on older vehicles and don't know exactly how the ZL1 system works but if you let the system drain completely then the master cylinder now has air in it and you need to bench bleed the master cylinder before bleeding anything else.

[Annatar]

Originally Posted by ariZona28

You probably already know but I'll throw it out for you just in case, don't forget the non-traditional sequence of RR, LF, LR, RF. Currently on pg 30 in the Z/28 section there's a thread pertaining to this. I'm pretty sure the ZL1 is the same.

Someone searching for this at a later time will find this information very useful, so it's good you stated it, and it bears repeating so it's searchable afterwards.

ZL1 brake bleeding sequence (ZL1 brakes' bleeding sequence, ZL1 brake line bleeding sequence, ZL1 brake lines' bleeding sequence)

1. rear right inboard caliper valve;
2. rear right outboard caliper valve;
3. left front inboard caliper valve;
4. left front outboard caliper valve;
5. left rear inboard caliper valve;
6. left rear outboard caliper valve;
7. right front inner caliper valve;
8. right front outer caliper valve.

Since I still do not have the shop manual, I did not know that I have to bleed the air out through the inboard caliper valves as well. I discovered it serendipitously watching a video filmed by someone who does have the shop manual for our ZL1's, so I wrote it down in my notes.

As soon as the 4 L of DOT 5.1 come in, I will try the above procedure.

I am almost certain I got the air into the master brake cylinder, as my reservoir was completely empty for two weeks. I am still not sure how to bleed the master cylinder...

Yes an active scan tool will turn the abs pumps on but they are not cheap.

Cost is of no concern to me in this scenario, and information is power in this case. Yes, I know that in that case I could have the vehicle towed to a shop, but that would be accepting defeat: I want to do this myself.

if you let the system drain completely then the master cylinder now has air in it and you need to bench bleed the master cylinder before bleeding anything else

That's the ticket. I will have to research how to do that. That will be "fun", as I don't have adequate working conditions, id est no bench.

I promised myself that when I buy my next house, it will either have room enough to build a garage or already have a garage large enough to equip it with multiple workbenches, tire balanacer and (dis)mounter, a lift and a paint booth. And of course I'll be getting a 1000+ liter compressor for the facility.

[silversleeper]

I think the master cylinder air bubble would be pushed out during the other purging. Air in any line would be pushed out. I could envision that it might take pushing on the brake pedal or pressurizing as mentioned above to make sure it pushed into the abs pump and past it.

[ZMEnow]

Originally Posted by silversleeper

I think the master cylinder air bubble would be pushed out during the other purging. Air in any line would be pushed out. I could envision that it might take pushing on the brake pedal or pressurizing as mentioned above to make sure it pushed into the abs pump and past it.

One of the best tools I purchased. Makes me smile every time I use it..


Mityvac MV6830 Professional Pneumatic Air Operated One Person Brake and Clutch Bleeder

[Annatar]

Originally Posted by ZMEnow

One of the best tools I purchased. Makes me smile every time I use it..


Mityvac MV6830 Professional Pneumatic Air Operated One Person Brake and Clutch Bleeder

I believe it. That brings us to the next point, U. S. Amazon won't ship most of the items to Europe, and there are usually several years between items available on the U. S. Amazon becoming available on other Amazon web sites around the world.

Needless to say, I didn't find the above on either the U. K. or the German Amazon, so I ordered this: Sealey VS820 Brake & Clutch Bleeding System. We will see whether its lid fits on the ZL1's brake fluid reservoir and how it will perform.

[ZMEnow]

Originally Posted by Annatar

I believe it. That brings us to the next point, U. S. Amazon won't ship most of the items to Europe, and there are usually several years between items available on the U. S. Amazon becoming available on other Amazon web sites around the world.

Needless to say, I didn't find the above on either the U. K. or the German Amazon, so I ordered this: Sealey VS820 Brake & Clutch Bleeding System. We will see whether its lid fits on the ZL1's brake fluid reservoir and how it will perform.

That Mityvac has been around for almost 10 years, so I would think it would be available through many others than Amazon.

[Shodown]

I have a similar air compressor powered brake bleeder that was about $70 on Amazon and worth every cent.

I had all my calipers removed to refinish them and didn’t have any issues refilling the system and bleeding them though.

[cdb95z28]

If you do not think you allowed air into the master cylinder, and it doesn't need bench bled, go out and engage the ABS. Repeatedly and heavily. Of course be safe about it, don't put it in the weeds, and don't do it where other drivers can see you, they might get freaked out, haha. You won't need a lot of speed to engage the ABS. Doing this eliminates the need to have the dealer cycle the ABS.

When I installed 6 pistons on my '14 1LE, I did an initial bleed and went for a drive. I purposely engaged the ABS multiple times. The pedal got soft. I went back home and re-bled. Pedal was rock hard, better than it was the OE 4 pistons. I've rebuilt my 6 pistons a few times since, and I do this everytime and it works.

I use the Motive Power Bleeder. Simple one man bleeding. Don't forget to clean out the residual brake fluid in those closed bleeders when finished bleeding. Remember, the bleeder seals at the bottom taper when closed. There will still be fluid left in it above the tapered seal. Wrap a rag around the little red spray tip of BrakLeen and give a quik spray into the closed bleeder. The rag will keep any fluid and Brakleen from spraying all over the place. Do it twice and let it dry out before reinstalling the rubber cap. Not cleaning out the fluid from the bleeder will cause corrosion, which acts as a threadlocker, which then causes the loosening torque to go up, sometimes breaking the bleeder.

You mentioned you didn't bleed the inner bleeder, that could be a large part of your problem.

[cdb95z28]

Dorman makes these nifty little rubber plugs to close off opened brake lines.

https://www.amazon.com/Dorman-Help-1.../dp/B0049DYJCE

[George-CZ]

When you used a vacuum bleeder, didn't it draw air around the thread of the vent screw? I've always seen bubbles in the hose

I see a better alternative in an overpressure system.
It is attached to a container that is under pressure, and I use a vent screw to drain the liquid through a transparent hose and watch to see if the bubbles are still rising. I'll go around the whole car and in a few minutes and done.