The 4 piston design on these cars was flawed from day one . the pistons have a very loose fit in the bores and have light springs behind them . The problem is caused as you drive and the runout from the rotors that can be caused by slightly loose front or rear wheel bearings . This causes the pistons to move in and out a small distance as you drive and they tend to take air into the calipers . The guy that invented the o ring caliper piston was a god send to the vette community ,,,, it just stops all the problems .

Geo

Just curious here.....after you bleed your brakes do you get a nice high tight pedal? Does it stay high and tight around town? Does the pedal drop happen ONLY after high speed driving like 60 mph on a turnpike?
All the answers that have been posted are good answers but if you can never get your pedal "correct" by bleeding the brakes, I wouold have to say rotor run-out ( over cut rotors ) or wheel bearings are not the culprit. If the pedal NEVER gets high and tight, I would look at an incorrect bleed or a bad internal seal on the master cylinder.
You did not mention it but are you losing any brake fluid? As George says, it does not take much to lose the brakes in these cars. George would know this better than I do, but I think you could also lose very small amounts of brake fluid from the master cylinder back into the power booster and end up with a low pedal from lack of hydrolic pressure.
Good Luck. It cost me $2500.00 by the time I finally got my brakes straightened out. Could not figure out what exactly was wrong...ended up replacing the entire system because everything in the system except the booster was bad.

Man the possibilities are blowing my mind. I never thought I would have to go to school to enjoy my dream ride.

Golly dang Glenn ah sur wood lak to be yur mekanik . Ah cood be rich . LOL just pulling your leg a bit ,,, as you say

geo

I bleed the system yesterday and there seams to be some improvment, though not what I;m used to. Looking forward to Adams results. Thanks to all who answeard my call for help. Hope to be of help to you all someday.

Ben81

Ben,
You may want to consider rebuilding the calipers... perhaps with the O-Ring Pistons I just bought. Here is a look at one of my calipers... you can see the gook and rust that has collected in the piston sleeve... pretty horrible:

(Click it to see a larger version)

Yea that does look pretty ugly. Will consider. thanks Adam.
Ben81

That is pretty much what all four on "The Toy" looked like last fall when I had everything apart. Some quality time with a toothbrush and brake cleaner got them cleaned up before honing all the piston cylinders. After putting eveything back together and bleeding the whole system the brake pedal was high and solid. Even after sitting in storage since November the pedal was still high and solid on the drive home last weekend. But I'm still going to flush the entire system again anyway before starting to drive on a regular basis.

Jim O.
Save the Wave...!!!

Jim a while ago I hit on a fast solution to doing the bores while tinkering around . I will take some pics to document the materials and process . It takes about 15/20 seconds to clean and polish each bore .

Geo

Here is the after picture following up the picture above

(Click it to see a larger version)


|UPDATED|3/21/2003 12:03:50 PM|/UPDATED|