L200 Sedan low brake pedal pressure
 

I've been a backyard mechanic for 30 years, 25 of which were also spent in the parts business, both retail and dealership levels, import and domestic. Felt like I knew my stuff until our L200 starting having low pedal pressure 5 years ago. It's a secondary vehicle so we have been chipping away at a solution as we have had time. Here are the details:

-Pedal went soft about five years ago to where only about the last 1/4 or less of travel would actually stop the car
-Within the last five years of intermittently troubleshooting, have replaced the following: rear shoes, wheel cylinders, brake hardware; front pads, calipers, brake hoses, ABS sensors; brake booster, check valve and hose; new mast cylinder three 3x (thinking we might have gotten defects); replaced ABS pump and brake controller with used unit from known working vehicle (no error codes showing either before or after installation).
-Have had the system bled about four times by two different service shops.
Nothing we have done will get our pedal pressure back. Been through everything I can think of. No adjustments have ever been made to the brake pedal throw.
WHAT AM I MISSING? Great little car otherwise, with only 100k miles on it. I'm second owner and first owner was a Saturn salesman who maintained it diligently. So car has never been abused and not in a harsh climate (live in Tidewater area of VA). Anyone have any ideas? Thanks for any input.

Is this a four-wheel disc abs vehicle?

For the disc brakes in the front, have you checked to make sure the Pistons are not overly extended? This can happen if the Piston seizes in place or hangs up. The inner pad will sit and wear against the rotor but never retract.

This leads to an increased system pressure that must be met to both
fill the void created by the overextended piston that is not normally there
AND
provide sufficient pressure through the other lines to the other three wheels to operate the the brakes at each wheel properly. At the same time.

check the pads rotors and calipers at the front wheels. If rear disc, do the same. If rear drum, pull the drums and check to see if the shoes are overly worn or if the wheel cylinders are weeping, or if the hardware is hung up pinning the shoes to the drum

My best guess is that there is something not right in the rear brakes.
Not assembled correctly.
Hardware issue or possibly the shoes are not adjusted properly.

Any updates?

Update.
 

So, took it to a GM dealer. Had them do the factory ABS bleed procedure. No change. They are stumped. Front disc, rear drums. Emergency brake works like it should so assuming rear brakes are adjusted properly. With vehicle off, plenty of pedal pressure. But as soon as you start the engine, pedal goes soft again. Stay tuned..,

Make sure they are not being stumped by the hour.... One and only one diag fee. If they don't know, move on

Indeed. Fortunately I am working with a service writer through a friend. And the service writer has an 01 version of my car so she has taken quite an interest in this. So she is currently only billing me for the factory ABS bleed procedure at the moment.

Are you saying that what is bothering you is that if you have your foot on the brake pedal when you start the car that the pedal moves down? If so, that's normal operation of a power brake system with a good booster and master cylinder. If it DIDN'T go down when you started the car, then you'd have a problem. Maybe I'm not understanding what you mean, but this is the impression that I'm getting. Maybe a defective check valve on the brake booster? Have you replaced that?

Maybe the rod from the booster to the master cylinder is misdjusted.

I remember at least one post on here in the last 2 years where somebody figured out after 137 troubleshooting sessions that it had to do with the connection between the power brake booster and the master cylinder itself. You can try searching on terms related to that. I don't remember which Saturn model it was. Today's GM techs are not going to know the finer details like this.

Unfortunately our L series specialist is on hiatus right now. He has factory service manuals 4 some of the L cars.

Hopefully he will be back soon.

I know Andy is missing in action for a while, but where the heck is Bones?