Brake problems.
Thread Starter
Cruising
Joined: Mar 2026
Posts: 14
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From: Texas
Brake problems.
Brakes go all the way down but they still break slightly. Inconsistent braking tho. Sometimes rock hard sometimes all the way down. Sorta. Spongey I guess? Anyway I have a new master cylinder installed and the brake fluid looks clean… did the brake guy just… not remove the air from the brake lines? Idk. 87 C4
Safety Car
Joined: Mar 2017
Posts: 4,202
Likes: 1,323
From: LeClaire Iowa
Brakes go all the way down but they still break slightly. Inconsistent braking tho. Sometimes rock hard sometimes all the way down. Sorta. Spongey I guess? Anyway I have a new master cylinder installed and the brake fluid looks clean… did the brake guy just… not remove the air from the brake lines? Idk. 87 C4
Thread Starter
Cruising
Joined: Mar 2026
Posts: 14
Likes: 0
From: Texas
Originally Posted by Whaleman;[url=tel:1609523827
1609523827[/url]]If it air in the system it does not sometimes become “rock hard”. The air is always there. Dan
Le Mans Master
Joined: Dec 2005
Posts: 8,578
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From: Communist Colorado
You need to be more descriptive with your issue if you want more help. When did all this start? Were there Brake repairs just completed? Brake guy??? Who would that be? Just off the cuff, Id say it almost sounds like you have a couple of issues. Soft spongy pedal is usually air in the system... Rock Hard,... that can be brake booster related. And absolutely change your flexible brake lines... your rubber lines are potentially 39 years old.....which Id almost bet are older than you...
At his point in the life of a C4, replacement of flexible brake lines should be considered part of the brake job.
At his point in the life of a C4, replacement of flexible brake lines should be considered part of the brake job.
Le Mans Master
Joined: Jul 2010
Posts: 6,589
Likes: 2,647
From: Lancaster, PA
Old brake line do not make spongy brakes that the pedal goes to the floor. Either air in the system or leaking MC (internally) or leaking calipers. Brake booster, MC is where I would look for problems if the system is fully bleed. If you have ABS, the controller could pump the system up even though it's not fully bleed.
Melting Slicks
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Just throwing this out there, but it took me three new master cylinders before I actually got a good one.
Parts like that are garbage right out of the box mre often than not these days.
Placing that aside, maybe find some gravel and work the ABS on it for a bit and then come home and bleed again.
Don't need to race around doing it, just enough to work the ABS on the gravel.
Bleeding these brakes are a chore because you have to do it a half dozen times or so all the way around to get a decent pedal. In my own experience anyway.
Parts like that are garbage right out of the box mre often than not these days.
Placing that aside, maybe find some gravel and work the ABS on it for a bit and then come home and bleed again.
Don't need to race around doing it, just enough to work the ABS on the gravel.
Bleeding these brakes are a chore because you have to do it a half dozen times or so all the way around to get a decent pedal. In my own experience anyway.
Last edited by Natty C; Mar 22, 2026 at 02:07 PM.
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Thread Starter
Cruising
Joined: Mar 2026
Posts: 14
Likes: 0
From: Texas
You need to be more descriptive with your issue if you want more help. When did all this start? Were there Brake repairs just completed? Brake guy??? Who would that be? Just off the cuff, Id say it almost sounds like you have a couple of issues. Soft spongy pedal is usually air in the system... Rock Hard,... that can be brake booster related. And absolutely change your flexible brake lines... your rubber lines are potentially 39 years old.....which Id almost bet are older than you... At his point in the life of a C4, replacement of flexible brake lines should be considered part of the brake job.
At his point in the life of a C4, replacement of flexible brake lines should be considered part of the brake job.
Thread Starter
Cruising
Joined: Mar 2026
Posts: 14
Likes: 0
From: Texas
Old brake line do not make spongy brakes that the pedal goes to the floor. Either air in the system or leaking MC (internally) or leaking calipers. Brake booster, MC is where I would look for problems if the system is fully bleed. If you have ABS, the controller could pump the system up even though it's not fully bleed.
Drifting
Joined: Sep 2022
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From: Liberty, SC
2023 C4 of the Year Finalist - Unmodified
You have another thread on an overheat situation. Does the 'spongey' 'all the way to the floor' correspond to when the engine overheated? The left side headers are close to the brake lines heat affects them.
Thread Starter
Cruising
Joined: Mar 2026
Posts: 14
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From: Texas
no, the two issues are unrelated (in my eyes at least). The overheating is a new development (to my dismay) while the brakes have been like this a couple months now (due to my inaction)
Le Mans Master
Joined: Jul 2010
Posts: 6,589
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From: Lancaster, PA
couple months back it started. Started as a loss of brakes on the highway on a hot day (where I live it’s consistently above the 100s F so that makes sense) brakes went to the floor but had very little at the end so I was able to make a stop. Local mechanic replaced my master cylinder a month after (sat for a while I’m a student with a part time job so I have to save for every part). After the master cylinder replacement the all the way to the floor and spongeyness went from just when I drove it for a while to all the time. No clue what a brake booster is I don’t know **** about cars that’s why im here in fact! And the flexible brake lines are the ones that go directly into the caliper right? The short ones? Not the ones that span the car length
Take the car back to the mechanic who replaced the master cylinder and ask for a working one. Should be under warranty.
Melting Slicks
Joined: May 2019
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From: Mid-Atlantic
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Most folks on here won't even let a ''mechanic'' touch their Corvette unless it's something more involved like transmission work or something like that. And there's a reason for that...
4th Gear
Joined: Feb 2016
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Same problem on my 87. Definitely related to air temperature. No issues until the outside temps get up to 95 or so. When it happens the master cylinder is burn-your-fingers hot. I see the response that the brake lines are close to the exhaust manifold, but the brake lines were close to the exhaust manifold when these cars were new, too.