Bleeding Master Cylinder & ABS
 

I own an SS and have never worked on the LT/LS, so I'm not sure if this post should be in the "General" forum. Nevertheless, I replaced the LR brake caliper on my 2009 SS. I have Brembos and bled the system using the sequence discussed HERE. Not once, but twice. I still have a soft pedal though. When I did my Brembo upgrade last year, and bled the system, I didn't encounter this much trouble. Here's a little more to the story...the car has been on jack stands for several weeks, slowly seeping out brake fluid from the leaky LR caliper (I was too busy to get to the repair). So it's possible the system lost too much fluid, resulting in an upstream air bubble in the master cylinder and/or ABS. Another piece to the story...the ABS light is on and was on well before the caliper started leaking. The ABS code is for bad LF wheel speed sensor, which I'm planning to replace very soon. Although the light was on, the pedal still felt fine before the caliper started leaking. So I essentially have two unrelated brake problems: first a bad wheel speed sensor (pedal still felt fine), followed by a leaky caliper a week later (pedal softened and still feels soft after the caliper repair and bleeding).

I'm going to work more on bleeding the brakes, but my main question now is how to bleed the master cylinder and ABS. After reading the service manual, it seems the process is to simply crack the lines at the ABS module, one-by-one, until fluid seeps out (i.e., gravity feed). But decades ago, when I worked in the GM garage, some cars required a special electronic bleeding process that was done with a Tech II. Does the HHR require this Tech II method?

It looks like you understand the how to's.
I would do your research with Google to find your answers to the year GM car your working on.
You might be overthinking the wheel here.

Unless the reservoir went completely empty how could air get in there?
With Brembo note that you bleed the inboard valve first.
Tech2 is only needed if you replace the EBCM, to program it.
Be sure to note which line on the EBCM goes where, it is not logical. But, it explains the bleeding sequence. Well, it is logical, if you accept the X sequence.

It's hard to see inside the reservoir and the fuse block is directly in front of it. Therefore, I do not know if it ran dry, but have suspicions.

Yup. I agree.

I did not replace the EBCM, so I assume I can just crack the lines to let fluid seep out a little bit (i.e., gravity feed).

My training tells me to replace calipers in pairs, so, that’s just me.
I suggest simple gravity bleed or a one person bleeder pump.
If you’re pedal pumping to bleed the brakes it is possible the pedal was pushed to far, if you suspect air in the system, start from scratch, bleed the master cylinder first then follow the bleeding sequence .

I replaced both rear calipers (one had a minor leak) on my SS with Brembo fronts a few weeks ago.

I filled the master cylinder and then used a vacuum pump bleeder on the rears. I kept bleeding until fresh fluid appeared at the rear calipers, as I wanted to do a flush at the same time.

After vacuum bleeding, I did a few pedal-push bleeder on/off cycles just to make sure. Then I bled the front Brembos to get new fluid through them also. I did top off the master cylinder once during the bleeding to make sure the master cylinder didn't go dry (as already mentioned it's hard to see the actual level once it goes below half full).

I didn't do anything with the ABS or disconnect the connections at the ABS module.

Everything worked fine after that.

Steve

This car's brake system is a nightmare. I've successfully bled all 4 brake calipers when I did the Brembo upgrade last year. It was pretty easy, but I didn't have the entire system open. But these latest repairs with the system running dry, have apparently let a stubborn air bubble in the system. I've tried bleeding 3 times but still have a soft pedal. One at a time, I crack the lines at the master cylinder to pump out air. I tighten the lines at the MC and then do the same at the ABS module, one line at a time. I tighten ABS and then do the 4 calipers (using the HHR's crisscross pattern discussed HERE). For each location, my assistant pushed the pedal down and I cracked open the port waiting until they tell me the pedal has fully depressed. Then I tighten the port and they release the pedal. I repeat several times at each port. Pedal is still soft though. What a nightmare. What is the trick to bleeding this system?

You need a power/pressure bleeder.

Don’t push the brake pedal all the way to the floor! Halfway is good! I learned on brake systems with cross brakes front to rear, and the trick was to put a piece of 2x4 under the brake pedal so you couldn’t mess up that valve system.
these new systems with ABS , it’s recommended to reverse bleed the system, pumping fluid up to the master.
I’ve also seen that the ABS module has to be bleed by the computer with a Scan tool.

https://www.chevyhhr.net/forums/www....ad.php?t=56744

A spongy brake pedal of course indicates air in the system, the trick is getting it out and not introducing more into the system.

CRAP! I asked that exact question further up this thread and was told the Tech II was only needed to reprogram the EBCM (if it had been replaced). Apparently, that was wrong and the Tech II is in fact needed. Oddly, the Mitchell's manual doesn't mention the need for a scan tool. Do you think a pressure bleeder would alleviate the need for the Tech II bleeding? (I don't have access to a scan tool)