Spongey Brakes

jclark · 07-02-12, 07:38 PM

I have a 70 Vette with a small block, 4 speed and manual brakes. Last year, I was having a problem with a low spongey brake pedal in which the brake light would come on when you push hard at a stop. None of the calipers where leaking so I thought the problem was a bad master cylinder. I replaced the master cylinder and blead the system. It seemed to work OK for several weeks, then I got the low brake pedal again.

I blead the brakes again this Spring and got a nice solid pedal for about a month, now it is spongey and low again. I have used DOT 3 fluid each time.

I also notice a lot of blackish gunk that came out of both rear calipars.
Any advice on what may be going on?

Should I have the system flushed and use a silicon fluid (Dot 5)?

I have only owned the car for two years, so I don't know what type of fluid was in the system.

Dan · 07-02-12, 08:27 PM

Try this:

corvetteforum.com/c3-tech-performance/2068532-1972-corvette-brakes-feel-spongy-what-to-look-for.html

tri power · 07-02-12, 09:14 PM

Yo Guy! Have the rotors checked for runout, .003 to .005 inches is O.K. any more and the pistons in the caliphers act like an air pump causing a spongy pedal. Frank

jclark · 07-03-12, 10:53 AM

Thanks for the suggestions

Can you recommend a shop that could check the brake system?

Also - can you recommend a shop that could install a new clutch?

Thanks
Joe

Bob Weiss · 07-03-12, 11:01 AM

Early Brake calipers can pull air in around the pucks in the calipers giving you a spongy pedal. Usually a result of pitted calipers bores and poor seals. Many peolpe get stainless steel lined calipers with o-ringed pucks. Should solve the problem and change the brake fluid ASAP!

thoyer · 07-03-12, 12:37 PM

Quote:

Originally Posted by tri power

Yo Guy! Have the rotors checked for runout, .003 to .005 inches is O.K. any more and the pistons in the caliphers act like an air pump causing a spongy pedal. Frank

Good advice.

Depending on where you live, A friend of mine has a shop in North Wales and he does a lot of muscle car work. He can easily handle you brakes and clutch.

Tom

92RAGTOP · 07-03-12, 02:35 PM

This is somewhat off the wall but if your brake line is routed anywhere close to your exhaust system your brake fluid will boil quickly creating spongy brakes then eventually no brakes.

jclark · 07-05-12, 08:04 AM

Quote:

Originally Posted by thoyer

Good advice.

Depending on where you live, A friend of mine has a shop in North Wales and he does a lot of muscle car work. He can easily handle you brakes and clutch.

Tom

Tom,
Could you give me the name of the shop and your friends contact information so I can give him a call.

Thank You
Joe

thoyer · 07-05-12, 07:22 PM

Quote:

Originally Posted by jclark

Tom,
Could you give me the name of the shop and your friends contact information so I can give him a call.

Thank You
Joe

Joe,

PM sent.

Tom

07-02-12, 07:38 PM	#1
jclark CCDV Club Member Join Date: Sep 2010 Posts: 11	Spongey Brakes I have a 70 Vette with a small block, 4 speed and manual brakes. Last year, I was having a problem with a low spongey brake pedal in which the brake light would come on when you push hard at a stop. None of the calipers where leaking so I thought the problem was a bad master cylinder. I replaced the master cylinder and blead the system. It seemed to work OK for several weeks, then I got the low brake pedal again. I blead the brakes again this Spring and got a nice solid pedal for about a month, now it is spongey and low again. I have used DOT 3 fluid each time. I also notice a lot of blackish gunk that came out of both rear calipars. Any advice on what may be going on? Should I have the system flushed and use a silicon fluid (Dot 5)? I have only owned the car for two years, so I don't know what type of fluid was in the system.

07-03-12, 11:01 AM	#5
Bob Weiss CCDV Club Member Join Date: Mar 2001 Posts: 2,200	Early Brake calipers can pull air in around the pucks in the calipers giving you a spongy pedal. Usually a result of pitted calipers bores and poor seals. Many peolpe get stainless steel lined calipers with o-ringed pucks. Should solve the problem and change the brake fluid ASAP! __________________ Bob Weiss CCDV Past Pres.(1993, 94 & 95), Past Board Chairman CCDV current Board Member CECF President NCM Founding Member and Past Ambassador

07-03-12, 02:35 PM	#7
92RAGTOP Super Moderator Join Date: Apr 2003 Posts: 4,021	This is somewhat off the wall but if your brake line is routed anywhere close to your exhaust system your brake fluid will boil quickly creating spongy brakes then eventually no brakes. __________________ 92 Red convertible Children in the dark cause accidents, accidents in the dark cause children. WWW.DonsShowboards.COM

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07-02-12, 08:27 PM	#2
Dan CCDV Club Member Join Date: Mar 2003 Location: Horsham, PA Posts: 283	Try this: corvetteforum.com/c3-tech-performance/2068532-1972-corvette-brakes-feel-spongy-what-to-look-for.html

07-02-12, 09:14 PM	#3
tri power CCDV Club Member Join Date: Jan 2010 Location: Bucks Co. Posts: 295	Yo Guy! Have the rotors checked for runout, .003 to .005 inches is O.K. any more and the pistons in the caliphers act like an air pump causing a spongy pedal. Frank

07-03-12, 10:53 AM	#4
jclark CCDV Club Member Join Date: Sep 2010 Posts: 11	Thanks for the suggestions Can you recommend a shop that could check the brake system? Also - can you recommend a shop that could install a new clutch? Thanks Joe

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