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Topic: Brake Issue

in Forum: C3 Engines, Driveline and Handling


Brake Issue

Posted: 8/19/05 1:54pm Message 1 of 6
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PLATTSBURGH, NY - USA
Joined: 11/21/2001
Posts: 54
Vette(s): 1978 Silver Coupe (Andy)L48 with leather Oyster interior.(Born March 22, 1978) 2003 50th Anniversary Edition (Annie) Born January 14, 2003
Not sure to post this question. The brakes in our 78 went out a few
months ago. Pedal got realy soft and spongy, the brake lite came on.
Checked the brake resevoir and it was full. This lead me to believe that
the master cyclinder was bad. so replaced it with rebuilt, bench bled the
master and then bled the lines at each corner after it was installed (both
bleeders). That lasted for about 100+ miles before it did it again, this
time purchased a new master, bled everything again. Once again it lasted
for about 100 miles and has done it again. Have I missed something
here, or am I just running into junk masters when I get them from the
local parts house? Any help would be appreciated.


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Brake Issue

Posted: 8/19/05 6:14pm Message 2 of 6
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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20226
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas
If you're not losing any brake fluid, then the masters are bad, or you're not getting ALL the air out of the system. Bleeding these brakes are a big PITA. (I love my pressure bleeder!)
It helps to use a large rubber mallet to tap on the calipers while you open the bleeders. This dislodges any air bubbles the might stick to the insides of the caliper.
Also, if the rotors have excessive run-out, then they will actually suck air into the calipers while you drive. This happens because the pistons in the calipers have springs that keep the pads against the rotors all the time, and if the pads are moving in & out due to rotor run-out, the pistons suck air into the calipers, and then eventually, the system is full of air again, and you get a spongy pedal.

If you are sure there is no air in the system, drive the car around the block a couple of times, and then bleed the brakes again. If you get any air, then you probably need to check the run-out on your rotors, and have them machined if you find them out of spec.


(btw.....the forum you were looking for is 'C3 Handling components') Adams' Apple38583.7616666667


Joel Adams
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Brake Issue

Posted: 8/19/05 8:29pm Message 3 of 6
Former Member
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PLATTSBURGH, NY - USA
Joined: 11/21/2001
Posts: 54
Vette(s): 1978 Silver Coupe (Andy)L48 with leather Oyster interior.(Born March 22, 1978) 2003 50th Anniversary Edition (Annie) Born January 14, 2003

After the new master was put in the brakes were bled, and it didn't last long.  The brakes were then bled again to see if I sucking air, and no air could be seen during the second bleed.  However, the brakes did go back to normal for a while then the same thing happened again.  During the initial bleed when the first master was replaced the right rear had a great deal of air in the line, more then was expected.  But since then its been pretty much the same on all corners.  I'm getting ready to put another new master into it from another supplier.  It should be here in about a week.  However, in the mean time checking the rotor run out is probably a good idea. 

Thanks




Brake Issue

Posted: 8/19/05 10:29pm Message 4 of 6
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North Hills, CA - USA
Joined: 6/12/2003
Posts: 515
Vette(s): 1972 T-Top

    I found that gravity bleeding worked the best for me....Got the best pedal I've ever had......Forget a Mitey-Vac...All that does is make your hands sore and tired......Just my 2 cents

 

                                                     reid





    Reid    '72 T-top

www.wildbunchcarclub.com

www.vannuyscruisingassociation.com


Brake Issue

Posted: 8/20/05 6:20am Message 5 of 6
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Waterford, MI - USA
Joined: 9/13/2002
Posts: 1755
Vette(s): 1973 Red coupe
I found the best way to bleed the brakes is to use a pressure bleeder. I have used the Mitey-Vac before but I never could get anything to happen trying to gravity bleed mine. Redwingvette38584.2647685185


Brian - NCM Lifetime Member

73 coupe L48, Flat-top pistons, Performer RPM Heads, Crane Cam and roller rockers, Holley 650 vac sec. Performer intake,
3.55 gear BTO 200-4R trans,
Leather seats, Seatbelt Plus 3point seatbelts, Pioneer CD player
Magnaflow Exhuast System

Dewitt radiator and dual electric fans
Borgeson Steering box
 


Brake Issue

Posted: 8/20/05 10:31am Message 6 of 6
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Joined: 10/21/2003
Posts: 1220
[QUOTE=Redwingvette]I found the best way to bleed the brakes is to use a pressure bleeder.[/QUOTE]       I agree!


in Forum: C3 Engines, Driveline and Handling


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