Hey all,

When I bought this car, the brakes were mediocre at best. I had never driven a C5 before, but I would think these brakes should work VERY well. My brother has C5 brakes on his 69 Camaro and they will suck your eyeballs out. As it was, they didn't work well enough to ever activate the ABS, maybe in the rain.

So I rebuilt them. Turned the rotors (GM slotted/drilled), Disassembled cleaned and painted the calipers, new pads (Power Stop Semi Metallic) and added Russell SS braided lines. Sucked the old dirty fluid from the MC and bled using a MytiVac bleeder. 3 times. The fluid is clean at each corner.

They don't work any better than before.

The pedal is hard with the car not running. Running, it feels soft for about one inch of travel, then feels solid.

Ideas? I suppose I could bleed the master cylinder, but it never went dry. Could the booster be bad? It doesn't leak vacuum. MC be dead? Not leaking, and doesn't sink to the floor. Pumping the brakes doesn't make a difference.

Ron

 

How did you turn slotted/drilled rotors?

 

Took them to Orileys.

 

Did they measure the rotors to make sure they were still within tolerance?

 

Buy new rotors, turning then is a waste of money and makes them more vulnerable to warping.

You probably need to bleed them more, do the pads bite hard or are they numb?

 

So after you did all this work, can you activate the antilocks now?

 

They were fine, only removed .010" per side.

 

Numb, and no, can't activate the ABS

 

What shape are your Tires in??

 

You have air in the system and i would also recommend a more aggressive pad.

 

When you turn rotors you have fine grooves left and your pads only touch the tops so braking is reduced due to less surface contact.
Then you further reduce contact patch by adding drilled and slotted, have you bedded your new pads yet?

The other question is how much vacuum do you have at idle, by your signature it appears you have a bit of a lumpy cam which will reduce the power assest.

C5 brakes are some of the best ever produced for a passanger car and in fact are the same ones used on Cadillac's being much heaver.

 

+1. Drilled rotors are for looks. Think of it this way, if you want more grip on pavement from your tires, do you add chunky off road tires, or do you go towards slicks? Drilled+slotted is like going to a chunkier tread instead of slicks. Plus, it reduces mass. Mass that absorbs the heat that stops you. Having said that, for a DD, you probably won't notice much, if any, difference.

If you can't stand on the brakes and get lock up or abs to kick in, then there's definitely something else wrong besides just the rotors. I also do not believe it's your pad choice. Someone else mentioned air, i agree with that, bleed the brakes again. Once you get bored of doing it and think you're done, do it again. Are you sure you didn't get any air in the master? It won't matter what else you do if the master has air in it.

I do a lot of autocross with my C5, and the stock brakes with EBC Yellow pads are enough to scare most people that ride with me.

 

I doubt it's air with a good solid hard pedal.

I would suspect it's the booster or that you're not getting power assist.

Second would be some kind of blockage in the line but you could probably tell if there was a blockage or not when you bled the brakes.

 

Thanks guys. I have always done my own brakes, and never had this issue. I know with new turned rotors and new pads, they take a few good stops to work, but it's just not happening here.

On the drilled and slotted rotors, I understand that it will reduce area. It has to. They were on the car and relatively new when I bought it. It also had the GM ceramic pads. The inside pads on the front had transferred pad materail to the rotors....they weren't right. Hence all the work. The calipers were also painted pale yellow and looked like hell. A brush job.....

I just went out and had a close look at the rotors. It appears the fronts are barely working. I washed the car the other day, and the water stains on the rotors where it drains out of the cross drilled holes are still there. As is the machining from the turning.

I will just go ahead and bench bleed the master cylinder. And go from there. My pads aren't fancy but should be fine.

Oh, vacuum at idle is 15", and of course goes up when driving, so I don't think that is the issue.

As far as bedding, they worked too poorly to bed! And first drive was with new engine combo, new A4 etc, there was a lot going on all at once. The brakes I noticed immediatly.

BTW, I have EBC Green with their rotors on my Cobalt SS Supercharged, great brakes! And excellent rotors. Would have loved to do this on the Vette, but very spendy!

And finally, this new setup is pretty much an animal. Even partially tuned in MAF only. I am very pleased. I really need these brakes to work correctly!

I'll let you know what I find.

Ron

 

When you rebuilt the calipers did that include the pistons? If not you have have some partially stuck pistons.

 

I disassembled the calipers. Everything appeared excellent. I did not replace the seals or boots. I can't see how anything could "stick".

 

Upon closer inspection, the master cylinder is leaking where it bolts to the booster. i should have notice this when I had the heads off etc. Maybe I did, but it just didn't register.

Now to find a new/rebuilt one for less tha $179! Ouch! (Summit, Dorman, $84)

I will let you know how it does, but I believe this is the issue.

Ron

 

Sounds like a good place to start! Glad you found the problem.

 

Well, it wasn't the master cylinder. Replaced it with new, no difference.
So I'm down to the booster I think.
Gads, I hate the shotgun approach.
The booster doesn't seem to hold vacuum very long. But I don't know what is normal here. Haven't worked on a power brake issue before.

They seem to work fine for normal stops, but I swear, the harder I try to stop, the worse they work.

Ron

 

With your engine off, try pulling off the brake booster vacuum hose. You should hear and feel a huge amount of air being sucked out. There should always be vacuum at that hose (engine on or off). Have you removed your intake recently? If so, have you checked the back of the intake to make sure that your brake booster vacuum hose is connected? Just some things to look at.

Like the others have stated, the brakes on these cars are the best in the industry. My eyeballs almost come out of their sockets when I hit the brakes.