Still having brake problems...

I hope I don't get in trouble for cross posting, but you guys have always been so helpful here. I also posted this in C5 tech.

Downshifting at max braking is a major freakin' pain...the brake is below the throttle...my ankle doesn't bend that way.


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Ok, here's the brief history
- hot track
- bad pad taper
- wierd pedal (would go all the way to the floor with the power on)

Got home figured it was the taper. Installed new rear pads, installed LG Wilwood front calipers, complete bleed...and I mean complete.

Went for a run to bed the new brakes and the pedal is still soft. I've bled like crazy, I do not feel there is any air in the lines, it feels like something else.

It is hard to describe, but the best I can do is this - the brakes feel like they engage at a normal pedal travel but it feels like I have to push a LONG way to induce heavy braking. I can achieve it, including ABS on dry pavement.

Another interesting symptom...while bleeding (all power off) when we let the pedal up you could hear a groaning noise coming from under the dash, i.e. as the master cyllinder was filling back up...

With power off the pedal is firm, which leads me to believe there is no air in the system. It's only when power is on.

Could this be a booster issue? Where is the vacuum for the booster?

Does any of this give anyone any ideas? I'm fixing to take it to the dealer, but with the new calipers I don't want them pointing to those first...sigh. I'm getting quite frustrated.

Thanks!
Jon

 

Jon any leaks? I had a leak today at the track and sounds like your problem.

 

No external leaks anywhere I can see. I even put fresh towels down below each caliper (even the stockers in back) to see if any drips were going unnoticed.

Bleeders are tight. All fittings are tight. I thoroughly cleaned everything before bleeding and before my drive and 2nd bleed.

After more listening it almost sounds like the groan is coming from the distribution block near the abs. Could there be air in there?

 

When you put the new rotors and pads on, did you crack open the bleeders. Sometimes, air can get into the ABS system. Then you have to bleed the ABS also, requires special tool as I recall.

 

anyone know the piston sizes of the Wilwoods??

 

Volume is near identical to stock front calipers. http://www.precisionbrakescompany.com/wilwood.html has diagrams which may show it as I remember

 

I think I've reached 3 conclusions on this -

1) Air in the ABS. The pedal is firm without power, so I'm inclined to NOT think this is the issue

2) The Master. They're pretty cheap (relatively), so I may just shotgun it and replace it and see how it feels.

3) The 2004s are just crazy boosted compared to the 2001s (which I've had and tracked). I'm kind of thinking this is just the way it is, and the pedal just isn't going to push back at me the way the 2001 did. If this is it, I'm just going to have to learn to drive it. More track miles will increase my confidence (which the pedal feel has not helped) and I'll move on

Thanks for all the advice and discussions. If anything significantly changes it I'll be sure to post. I love the AC/RR section...it's my new favorite place Nice to take a brake from rusty rotors and painting calipers and decals

 

What method are you using to bleed the brakes? I had problems like that until I started using a power bleeder.
Scott

 

I am like you and would go for the master cylinder first.

 

Standard pedal bleed, in the sequence for 2001+. Wife puts pressure on pedal, open screw, close before wife lets up, allow wife to let up. Wait etc. I've tapped calipers etc. to get all air out.

What power bleeder are you using? Did this really make a difference?

 

Kent-Moore makes an adapter that fits on your master cylinder in place of the cap which allows you to attach an air hose to it (at about 10-15 PSI) to pressurize the master. Then all you do is follow the normal sequence and open each bleeder (one at a time) until you are satisfied that there is no more air in that line.

The K-M adapter is about $70 and you have to order it direct, some guys have modified a second master cylinder cap as a less expensive alternative.

If you do not have an air compressor or want the ability to power bleed at the track, Motive makes a plastic power bleeder bottle to pressurize the master or some guys have modified garden sprayers to do the same thing.

This is definately a better way than the old pump the pedal methodas far as getting all the air out plus you don't have to bug the wife to help you bleed brakes anymore which leaves you free to bug her about other favors.

Scott

 

Yah, I think I'm out of favors after the last 3 days

Thanks for the inputs!