brake pedal too soft
 

We are new owners of an '08 SS. Sometimes when first starting the engine, and even before startup, the brake pedal drops very low. Once underway, the pedal feels OK although, overall, it seems a bit spongy. It stops OK so this is the only symptom. Reading through the forum I can see lots of folks with rotor issues but nothing like this. Will probably take it to the dealer but it is intermittent- and we know how that usually goes ! Any suggestions ?

spongy pedal -> bleed the lines

That was my first thought - it's just that it's intermittent and my exp. with air in lines is it stays spongy. But you're probably right.

probably not air but water... once the fluid absorbs it, pedal travel can go downhill pretty quickly... not something to mess with!

hope you get it worked out.

I'd suspect more of a booster issue. Not really a problem but simply pressure being built up by the vacuum when you start the car. You first press the pedal when the car is off and you have a firm but long throw pedal as the stored vacuum is depleted, start the car up and and it's rock hard for a moment then softens up and raises some also. Just a guess from here.

As for effectiveness I'd suspect like more oem parts they put in a lot of piston area on a moderately sized rotor and you'll never get the true feeling you want. Mostly because oem's tend to build to the masses who don't want a "hard pedal to push" (granny can't do that you know) so they compromise and make it mushy but strong in clamping.

I'll work on a kit for the SS with its new spindles (can't use a good thing from the current car eh GM? pita) and we can resolve this pretty quickly.

PROCEDURE AS POSTED FOR GM TECHS TO FOLLOW


Inspect the travel and feel of brake pedal applies. Perform the following:

Apply the brake pedal several times to fully deplete the power reserve.
With power reserve depleted, apply the brake pedal with light, steady pressure and hold for 15 seconds. Observe pedal travel and feel.
Apply the brake pedal with light, steady pressure, then without pumping the pedal, reduce pressure and reapply pressure several times. Observe pedal travel and feel for each apply.
Apply the brake pedal slowly, then release and apply the pedal quickly. Observe pedal travel and feel for each apply.
Did you complete the brake pedal travel and feel inspections?
Go to Step 3
--

3
Inspect the hydraulic brake system for the conditions listed, based on the following symptoms observed during the pedal travel and feel inspections.
• Pedal feel was spongy.

- Air in hydraulic system

- External brake fluid leaks

- Soft, weak or damaged hydraulic hoses; expanding under pressure

• Pedal fell away and/or traveled to or almost to floor.

- External brake fluid leaks

- Poor brake fluid quality; low boiling point

- Internal brake fluid leaks; improperly functioning master cylinder

• Pedal was somewhat firm then dropped slightly, or pedal rose with successive applies, or pedal travel was different between slow and quick applies.

- Internal brake fluid leaks; improperly functioning master cylinder

- Poor brake fluid quality; low boiling point

- Binding wheel cylinder pistons, if equipped

• Pedal returned to rest slowly after any of the applies.

- Internally damaged flexible brake hoses; hindering fluid return

- Binding caliper pistons

- Binding wheel cylinder pistons, if equipped

- Internal brake fluid leaks; improperly functioning master cylinder

Repair or replace components as necessary. Refer to Hydraulic Brake System Diagnosis .
Re-inspect brake pedal apply travel and feel.

ours went into the shop for the same problem and they found the the master cylinder leaking internally