89 vert brakes. Need help!
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89 vert brakes. Need help!
89 vert. Brakes work fine driving around town. If I go on a cruise, the first time I hit the pedal, it goes down quite aways. Next pump they are back to the top. I have already put a new master cylinder on it. Pads are all new. Rotors are new. Any suggestions are greatly appriacted.
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brakes
No air in lines. I had this issue before I replaced Master cylinder. Bench bled new MC. Could this have anything to do with ABS stuff ?
Heel & Toe
Joined: Sep 2007
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From: Little River South Carolina
I had the same thing happen on a 92 non corvette chevy. The master cylinder brake fluid went low and sucked air in to the system. I replaced the master cyl and bench bled as per instructions, then bled the brakes when everything was back together. The brakes still went soft after driving a while. But then I bled all 4 brakes again and there was still more air in there! Especially in the front left side. Bleed the brakes again. There are tiny air bubbles in there you couldn't see the first time. Just make sure the master cyl doesn't go dry. This is a 2 person job. Hope this helps, Brad
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Le Mans Master
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From: One day you're a Comet...the next day you're dust... Arkansas
89 vert. Brakes work fine driving around town. If I go on a cruise, the first time I hit the pedal, it goes down quite aways. Next pump they are back to the top. I have already put a new master cylinder on it. Pads are all new. Rotors are new. Any suggestions are greatly appriacted.
Melting Slicks
Joined: Jun 2004
Posts: 3,253
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From: Castro Valley CA
This is probably very unlikely, as yours is a street driven car but...
I race my 94 LT1 with J55's and when one or both of the calipers spread through thermal distortion and take a permanent set they will exhibit the symptoms you describe. It is due to the increased pad knockback that occurs when the calipers are warped. As I said, very unlikely; but you can confirm by measuring the interior dimensions of the calipers, they should be parallel between the "ears" and the piston face.
I race my 94 LT1 with J55's and when one or both of the calipers spread through thermal distortion and take a permanent set they will exhibit the symptoms you describe. It is due to the increased pad knockback that occurs when the calipers are warped. As I said, very unlikely; but you can confirm by measuring the interior dimensions of the calipers, they should be parallel between the "ears" and the piston face.
Melting Slicks
Joined: Apr 2002
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From: St. Charles, MO Route 66 Corvette Club
Mike:
I have been working on auto brake systems for over 40 years (now.....don't think I am old!!!) and the best method I have found to bleed the brake system is the use of a tool called "Mityvac" (http://www.mityvac.com/). However, if you use the tool as shipped, it has a serious problem in that it sucks air from the brake bleeder screw as you purge each caliper. To solve this problem, get an extra brake bleeder screw and drill a hole straight through the bleeder screw. To purge a caliper, remove the original bleeder screw and insert the drilled screw. Suck fluid from that caliper until you get fresh fluid and NO bubbles. Remove the drilled screw and replace the original. As you remove the drilled screw, you will loose a little fluid and air will not enter the system.
The "el cheapo" Mityvac is plastic and costs about $35 while the best is aluminum and costs about $75 at Sears. You will use this tool many times in the future.
Using this tool is easy and is a one man job.
I have been working on auto brake systems for over 40 years (now.....don't think I am old!!!) and the best method I have found to bleed the brake system is the use of a tool called "Mityvac" (http://www.mityvac.com/). However, if you use the tool as shipped, it has a serious problem in that it sucks air from the brake bleeder screw as you purge each caliper. To solve this problem, get an extra brake bleeder screw and drill a hole straight through the bleeder screw. To purge a caliper, remove the original bleeder screw and insert the drilled screw. Suck fluid from that caliper until you get fresh fluid and NO bubbles. Remove the drilled screw and replace the original. As you remove the drilled screw, you will loose a little fluid and air will not enter the system.
The "el cheapo" Mityvac is plastic and costs about $35 while the best is aluminum and costs about $75 at Sears. You will use this tool many times in the future.
Using this tool is easy and is a one man job.
Last edited by Sam Lam; Jan 18, 2008 at 10:50 PM.
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brakes.
Thank you Sidney. I KNOW I dont have any air. Im going to look at my calipers. That sounds like whats happening. Thanks everyone for your input. This is an awesome forum to belong to because of all of your knowlage.
Melting Slicks
Joined: Jun 2004
Posts: 3,253
Likes: 2
From: Castro Valley CA
Measure it and report back. If you have any question PM me and I will give you my phone number. Also look at the wear pattern of the pads, if they are tapered circumferencially, it is definitly distorted calipers.
Last edited by Sidney004; Jan 17, 2008 at 10:37 PM.
