1990 Corvette Brake Issues
Thread Starter
Instructor
Joined: Oct 2002
Posts: 123
Likes: 8
From: Orange County NY
1990 Corvette Brake Issues
I have been slowly restoring the 1990 Corvette I inherited, it is a blast to drive now. The front seal on the transmission was leaking, so the transmission had to come out. While it was out, I had them install a B+M Stage 2 Shift Kit. Very fun. My problem is the brakes. Less than 1,000 miles ago, though 4 years ago, my friend took this Vette to his local Midas shop and had the pads and rotors replaced (cheap stuff). After sitting for months and months outside, they have cleaned up well with some driving, but I will tell you, the car is not Vettelike when braking. It really is slow to respond during braking and I have to push REALLY hard if I want it to stop fast, which it doesn't actually do. I am keeping everything in this car completely stock, so I ordered AC Delco Durastop Rotors and the more expensive Durastop Ceramic Pads. The calipers appear to be original, so I plan to swap them out with rebuilt ones with stainless steel hoses. I plan on driving it the way it is until it goes away for the winter, then doing all the brake work in the Spring. My question is this: do you think these upgrades from where it is now will fix the problem? Or do I need to get the original, 23 year old master cylinder and brake booster involved too? Car has 70k miles on it and was always babied. Thanks
Team Owner
Joined: Sep 2003
Posts: 25,393
Likes: 2,741
I have been slowly restoring the 1990 Corvette I inherited, it is a blast to drive now. The front seal on the transmission was leaking, so the transmission had to come out. While it was out, I had them install a B+M Stage 2 Shift Kit. Very fun. My problem is the brakes. Less than 1,000 miles ago, though 4 years ago, my friend took this Vette to his local Midas shop and had the pads and rotors replaced (cheap stuff). After sitting for months and months outside, they have cleaned up well with some driving, but I will tell you, the car is not Vettelike when braking. It really is slow to respond during braking and I have to push REALLY hard if I want it to stop fast, which it doesn't actually do. I am keeping everything in this car completely stock, so I ordered AC Delco Durastop Rotors and the more expensive Durastop Ceramic Pads. The calipers appear to be original, so I plan to swap them out with rebuilt ones with stainless steel hoses. I plan on driving it the way it is until it goes away for the winter, then doing all the brake work in the Spring. My question is this: do you think these upgrades from where it is now will fix the problem? Or do I need to get the original, 23 year old master cylinder and brake booster involved too? Car has 70k miles on it and was always babied. Thanks
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
Maybe. Or junk pads. Crap auto=parts store pads can definitely make the system perform poorly.
I've never experienced this, but I've read enough posts to feel it's worth passing along; find a loose gravel/sandy place and hammer the brakes to invoke ABS. Apparently that can help "fix" a poor barking performance or hard pedal issue. If that doesn't fix it, upgrade the pads to something much better and newer. Texture or replace the rotors and break-in the parts together.
Your problem isn't likely the master cylinder; that manifests itself in a soft pedal, or a "sinking' pedal when applying steady pressure. The booster is easy to test; if you can feel the power assist working (less pedal effort when running as when not), not hear vacuum leak when pressing the pedal, it's working.
I've never experienced this, but I've read enough posts to feel it's worth passing along; find a loose gravel/sandy place and hammer the brakes to invoke ABS. Apparently that can help "fix" a poor barking performance or hard pedal issue. If that doesn't fix it, upgrade the pads to something much better and newer. Texture or replace the rotors and break-in the parts together.
Your problem isn't likely the master cylinder; that manifests itself in a soft pedal, or a "sinking' pedal when applying steady pressure. The booster is easy to test; if you can feel the power assist working (less pedal effort when running as when not), not hear vacuum leak when pressing the pedal, it's working.
Thread Starter
Instructor
Joined: Oct 2002
Posts: 123
Likes: 8
From: Orange County NY
Well, I can't find anything leaking and I haven't noted a vacuum leak anywhere. The brake pedal is not soft and doesn't sink to the floor, however, I do have to press pretty hard to make the car stop. Not hard enough however to think there is zero power assist. So hard to know without driving a perfect one. I am putting all the new brake stuff on in the spring, not just for performance, for the look through my new ZR1 style reproduction wheels. I need it to brake like a Vette should though.
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
Well....I told you a couple things to check/try, above. Doesn't sound like you have follewed my advice. With regard to the power assist and hard to know without driving a perfect one, it's not hard. I told you how to check it. Park the car, turn it off. Pump the brake pedal about 5 times. W/in those 5 pumps (probably after about 3), your power assist will go away -if it's working. If your pedal feels the same for all 5 pumps, then you never had any power assist. If you can feel the change, then you did and it was working. If it's working, and "holds vacuum" for a while (hours) and still provides those same 2-3 pumps with power assist, then the power booster is effectively working as well as any. Thy don't "wear out", or get weaker...they work 100%, until the diaphragm tears or the housing cracks, then they don't pass the test that I have illustrated for you.
Max G’s
Joined: Nov 2008
Posts: 2,751
Likes: 79
From: Monroe OH
NCM Sinkhole Donor
I would suggest to just flush the fluid via gravity bleeding is optimum and replace just the pads with some good pads such as Hawk HPS pads. FYI, the carbon fiber pads are only going to be an advantage in higher temp applications, so unless you plan to race it for hours on track, stick with metallic materials.
Race Director
Joined: Aug 2000
Posts: 11,470
Likes: 764
sounds like my steel blue 90. I did just about everything to get that thing to stop like my 85, but never could figure out the braking system. when I bought the car, I did notice the brakes, but figured it was a combination of some simple things - pads, rotors, maybe brake lines. no matter how much I stood on the brake pedal, I never could get the ABS top kick in - just couldn't lock the wheels up. I replaced the pads (two different premium sets), rotors, S/S brake lines, new delco master cylinder, brake fluid flush, and bled the brakes twice, and had two different shops check the ABS system. I did get some improvement in stopping , but nothing like what a corvette should be, and nothing like my 85. after everything I did, I could get wheels to lock and the ABS to kick in, but only after really standing on the pedal. the final thing was to look into was the brake booster, but I ended up selling the car - just too many issues. too bad, cause my SB 90 was a looker. my white 90 is 110% better in the braking department, but still not as good as my 85. I do plan on new pads and rotors though. good luck - keep us posted!
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