I have built my '94 Z28 into a road race car.
Left the stock LT1, 6-spd, and 3.42 gears.
Put on headers and 3 inch exhaust, and K&N open air cleaner.

Installed 13" ZR1 rotors and Wilwood calipers on the front, stock 12" rotors and calipers on the rear.
Use Wilwood black pads on the front, Hawk HP+ on the rear, with Motul 600 synthetic fluid.

When first built the car, the brakes were good... hard pedal about 2/3 way down.

Now, after 4 or 5 events, I can't get a hard pedal no matter what we do.
Rotors are still great, pads are still more than 60% left, no leaks whatsoever, bled the system until we are nuts. Changed the fluid completely... no difference. Installed a new master cylinder... no difference.

Still get a spongy pedal... the brakes work... but pedal is very spongy... and I can actually push down to the floor if I push hard enough. I couldn't do this when they were originally installed.

We are going nuts trying to figure out what we can try next.

Any ideas????? Anyone?????

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Gary - Richmond, B.C. Canada
My Site:http://www.pgwatson.com
EMail: gary@pgwatson.com
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NTMD8R
'78 Silver Anni (Killer AutoXr)(5 yrs)(gone)
'65 Red convertible (Killer AutoXr)(6 yrs)(gone)
'88 Charcoal Coupe (SoSo AutoXr)(2 yrs)(gone)
'92 Black convertible (Killer AutoXr)(6 yrs)(gone)
'67 Black Convertible (fun car)(5 yrs)(my wife's)
2K Black Convertible (6 Spd, Z51, HUD, 3.42, Active Handling, Loaded)(Killer AutoXr)(Vortex, Corsa Indy, CAGS defeat, Lowered, BPP Exhaust plate, PIAA Lights, Mallett396 18" Wheels, BFG-GForce tires, Modified Altec Fender Guards, Ripper Shifter, Custom Rollbar)
'94 Camaro Z28 Coupe, 6Spd being prepared for Road Racing
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See NTMD8R - Gary

 

My brakes were spongy with Motul 600. I switched to 5.1 and rebuilt the front calipers (just to replace the burnt dust boots) and it was 100% better.

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2001 Trans Am M6

 

Check for caliper or mounting bracket flex. Also take a look at your firewall where the booster attaches, it isn't very sturdy and could have cracked. Ever step on the brake pedal with the hood open and watch the master cyl. and booster move due to firewall flex? Spooky!

 

Here's a long shot. I have a Honda with 150K and the brakes went spongy. Turned out that the master cylinder was worn out. If you have lots of miles, maybe your master cylinder is not up to the task.

 

I've heard old rubber brake lines can balloon under pressure causing that symptom. You could have someone press while you watch. Some folks report a much firmer pedal after switching to stainless braided lines.

 

I have a 94 that I road raced back in 94-96. I am currently rebuilding it for next season. I had the same problem with my car and the stock brakes. I tried SS lines, race pads, ducts, fluid, replaced the booster, master cylinder and bled the system forever. I always got a soft pedal. Then I took it to the dealer for the hell of it. They knew I raced it locally but were cool. They told me they would not do it again but they relaced the rotors and pads with stock pieces and when I got it back the pedal was as hard as a rock. But it went away after a bit of hard lapping. When I asked a local pro F-body racer named Joe Aquilante what he thought, he said you have to have the Tech 1 diagnostic tool to properly bleed the ABS. The middle piston in the ABS block has to be reset to the bottom before bleeding. He also ran PBR 13" Corvette brakes but he said he could run them hard all day in an enduro without a soft pedal. I have since removed the ABS and have installed a manual prop. valve and C5 brakes up front. I will have to wait until next year to determine if they work. As for the spongy feel, have someone use a Tech tool and bleed them that way. I will bet your pedal comes back at least until you hammer them again.

[This message has been edited by chrisbarr (edited September 12, 2002).]

 

someone mentioned for at least ls1 cars(dunno if the abs changed) bleed your brakes normally, then drive your car over about 10 mph at least, slam on your brakes to create an ABS event, pull back in your garage and bleed your brakes againt without turning your engine off it would do the same thing as the tech tool... something like that, never tried it before.. anyone else hear this?

 

Ken... I know some LS1 guys that do that...but I thought the LT1 ABS module had a bleeder on it.

I have never messed with mine.



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96 Z28 M6-Lots of bolt ons!

Smitty's Speed Shop
My 1996 Z-28

Road Racing Pics

 

anyone know how to reset the middle ABS piston?

 

As I stated above, you will need a Tech 1 tool(or similar) that the dealer uses. It plugs into your data port below the dash and electronically resets the piston for bleeding. Others may have been successful bleeding without doing this but I got my info straight from a GM dealer owner/pro F-body racer. All I can say is it did wonders for my pedal.