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12-10-2017
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#1 |
Join Date: Apr 2007
Location: Beaufort, SC
Posts: 7
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Front Brakes Lock Up after a few stops
My front brakes lock up after a few stops. This is so bad that the car comes to a complete stop and can't be driven. If a wait a few hours the brakes release by themselves.
I have replaced both front brake lines but the problem still remains. If I crack either front bleeder screw both sides release. This would seem to indicate a problem with the master cylinder or the ABS unit. The car is a 94 with 18k miles. The problem occurred when the car sat in storage for about a year. My current theory is that if I crack one of the lines at the master cylinder and the brakes release, then it is probably the master cylinder causing the problem. If they don't release, then its probably the ABS unit. I would appreciate it if someone could let me know if this approach makes sense and any other likely causes. Also if anyone has a diagram of the brake line routing from the Master cylinder down to the ASR and ABS unit the brake calipers, it would be useful. |
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12-11-2017
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#2 |
 
Join Date: Dec 2007
Location: NYC
Posts: 1,188
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Re: Front Brakes Lock Up after a few stops
Its the master cylinder
__________________
90 Chevy ZR1 LPE #2315 'SOLD' 90 Chevy ZR1 LPE #2774 'SOLD' 91 Chevy ZR1 Callaway aerobody 91 Chevy ZR1 #1512 91 Chevy ZR1 #951 95 Chevy ZR1 #338 'SOLD' 91 BMW 850i 94 BMW 850csi 95 BMW 850csi 94 Lotus Esprit S4 07 Benz CLS550 06 BMW M5 "SOLD" |
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12-11-2017
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#3 |
 
Join Date: Jun 2006
Location: Sparks, NV
Posts: 2,852
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Re: Front Brakes Lock Up after a few stops
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90'ZR-1 #1461 Red/Black Ported Intake, Degreed Cams, OBX Headers & Exhaust, Fidanza FW, Secondary Delete, Custom tune, C6 GS Wheels. Sold 08 C6 Z51 Crystal Red Metallic Sold Vararam Intake, Tune, Sold 05 C6 Z51 Red/Black Sold 90'ZR-1 #1723 Black/Gray Sold but not forgotten 91' Z51 L98 White Vert. My First, you always remember your first. Sold. |
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12-11-2017
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#4 |
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Join Date: Apr 2007
Location: Beaufort, SC
Posts: 7
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Re: Front Brakes Lock Up after a few stops
Thanks, I just ordered one and will post the results once I install it.
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12-14-2017
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#5 |
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Join Date: Apr 2007
Location: Beaufort, SC
Posts: 7
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Re: Front Brakes Lock Up after a few stops
It was the master cylinder. I replaced it and the lock up problem is solved. I now have the red brake light in the instrument cluster illuminated. Apparently there are 3 things that can cause this.
Parking brake switch .... didn't mess with it Low Fluid warning switch Brake pressure switch A little more diagnosis is necessary. I found this post which was helpful https://www.corvetteforum.com/forums...-light-c4.html Last edited by johntorg; 12-14-2017 at 05:15 PM. |
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12-14-2017
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#6 |
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Join Date: Dec 2007
Location: NYC
Posts: 1,188
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Re: Front Brakes Lock Up after a few stops
Did you reconnect everything? bleed the system top off brake fluids??
__________________
90 Chevy ZR1 LPE #2315 'SOLD' 90 Chevy ZR1 LPE #2774 'SOLD' 91 Chevy ZR1 Callaway aerobody 91 Chevy ZR1 #1512 91 Chevy ZR1 #951 95 Chevy ZR1 #338 'SOLD' 91 BMW 850i 94 BMW 850csi 95 BMW 850csi 94 Lotus Esprit S4 07 Benz CLS550 06 BMW M5 "SOLD" |
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12-14-2017
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#7 |
 
Join Date: Jan 2006
Location: Niceville
Posts: 998
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Re: Front Brakes Lock Up after a few stops
I've been fighting this a while on a buddy's car. It is most likely the proportioning valve that repositioned while bleeding (air in system). I have one more trick up my sleeve before I throw in the towel.
Turn key on--don't crank. Make sure parking brake is off. Then unplug switch on mater cylinder on the proportioning valve cylinder (the white switch you traded out). Did brake light go out? Ted |
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