what a guy! maven awesome !

 

I do what I can

 

Okay, I actually need a little more info here.

I had my front calipers off the car for 24 hours once when I painted them. The lines to those wheels drained. I have ABS. When I put everything back together, I did a resevoir service and manual bleed. I don't have a vacuum bleeder. I made a couple of How-To threads on the subject.

My brakes work, but every now and then during a hard corner or aggressive braking, I get a DIC warning of "Brake Fluid" and the brake annunciator light. It goes away after about one second.

I am convinced that I got an air bubble in the ABS unit somewhere that I can't bleed out manually, but my dealership has told me that I don't need a shop-done bleed.

Tell me about the Tech-2 bleed procedure, and tell me if you think I need it, because I really think I do.

 

Wow, this so not me, but... BUMP.

Come on, somebody has to have an answer for me.

 

That just sounds like the brake master fluid level sensor. Is your brake fluid level slightly
low? If so top it off and test drive in the same conditions that make the light come on.

 

Definitely not the problem. Resevoir is full. I even had a software reflash done that apparently addresses this kind of issue with no help.

 

Check the ground under your seat.

Disconnect your brake fluid level switch, see if the problem still occurs with swtich disconnected, if it doesnt, you need a switch.(or possibly clean out old one)

Disconnect your park barke switch, see if it still occurs with park brake switch disconnected. if it doesnt you need to fix the park brake switch.

If it still comes on with both disconnected, you either have an EBCM, BCM or IPC issue, or a short to ground.

 

Okay, I'll do all that. The ground under my seat was disconnected when I did my sound proofing, but I did put everything back together, and the problem did exist before then. I'll disconnect those sensors and get back to you. It might be a week or more, it doesn't happen that often.

 

This is great info!

 

Here's a quickie question. Since the BPMV is replaced by the ABS unit on ABS cars, is the bleeding order the same, and does the TECH 2 need still not apply?

 

The BPMV is the abs.(Non ABS cars have a proportioning valve, and still use the same diag split) The only reason you need a Tech2 is if you have ABS

 

Which I do, which is why I think there is a bubble in the ABS unit that I can't bleed out.

 

I understand, but the BRAKE light wouldnt come on for that.

 

Okay, so you are telling me that the only system monitors that would create a DIC message of "brake fluid" are in the resevoir, and theres nothing in the ABS valve unit? If so, thats a good thing, because I have plenty of fluid. I guess it's possible the aggressive cornering could be splashing the fluid off of the sensor just long enough to set off the annunciator.

 

So I have a confession to make.

I never did disconnect anything. Sorry, I'm horrible.

However, I have been able to consistently reproduce the problem. It only occurs during aggressive turning to the right. I don't even have to be going that fast really. If I just pull the car hard over right, the alarm will sound. So I'm pretty confident at this point that it's just fluid sloshing off the level sensor in some way.

So here is my request. Somebody else go do this and see if you can get your car to do it.

 

I develop ABS systems for a living (we dont make the cobalt one tho), and when we bleed them on the test stand we cycle all valves with pressure applied and then bleed afterward to get all of the air out. If you keep your system full, you should not have to do this, but if you disconnect the master or anything before the ABS HCU, then you should bleed the system. There are several air traps that will reduce your pedal feel.

 

Thank You for your input.
I use a Motive Products pressure bleeder to change fluid after track/school days.
Would a pressure system like that with it's 5 to 10 PSI get rid of any trapped air in the entire system ?????

Thanks

 

We use approx 3-5 bar to do our initial bleed, then use 100 bar or so to do our final bleed. Unless you are introducing air into the system, this should be fine. It takes much more effort when you start with a dry system. Sounds like you are just pushing the old fluid through without disconnecting anything. Should be good.

 

At 3-5bar, Are you using a bladder type(fluid chamber/air chamber) pressure bleeder to do this?

At 100bar I can only assume you are using the master cylinder to generate that pressure, or do you have specialized full hydraulic bleeding gear to do that?

I cant imagine youd be using compressed air of any kind at those pressures as youd just be aerating the fluid. (fluid aeration is an issue even at pressures below 2 bar in a single vessel/chamber pressurized bleeder(such as the Motive unit referenced earlier)

 

You are correct in your assessments. I can get every bit of air out using these methods when cycling the solenoids before final bleed