Brake problems - serious
Melting Slicks
Joined: Jul 2008
Posts: 2,268
Likes: 142
From: Ottawa Ontario
Manual bleed or vacuum bleed? Sometimes, with a manual bleed, the brake pedal gets pushed further than usual which can damage the seals in the master cylinder.
Instructor
Joined: Nov 2013
Posts: 154
Likes: 1
Thread Starter
Advanced
Joined: Oct 2014
Posts: 82
Likes: 0
From: Marietta Georgia
the brakes are spongy and go all the way to the floor at times. I have to pump up the brakes to get a good hard pedal. I did put on a new master cylinder and completely bled brakes (starting from right rear, left rear, right front left front) until all the new fluid replaced the old fluid. No all the fluid is good and clear.
Instructor
Joined: Nov 2013
Posts: 154
Likes: 1
Bleeding the brakes on and older gm can really be a pain in the rear. Sometimes especially if you replaced the master. You have the right sequence RR LR LF RF if you have no leaks you just have to keep on bleeding there is air still in there. Sometimes it takes an hour or more with 2 guys to get those old systems to bleed out and the pedal solid again.
If you didn't bench bleed the master before Installing the air could be trapped in the master. Go around and bleed with 2 people with the up down method. Open bleeder press pedal down, close bleeder raise pedal. Do this until you get a more solid pedal. I've even had some luck doing this with the car running, helps move more of the air/fluid out. That's the best way I've found to bleed them, hope this helps.
If you didn't bench bleed the master before Installing the air could be trapped in the master. Go around and bleed with 2 people with the up down method. Open bleeder press pedal down, close bleeder raise pedal. Do this until you get a more solid pedal. I've even had some luck doing this with the car running, helps move more of the air/fluid out. That's the best way I've found to bleed them, hope this helps.
Drifting
Joined: Jul 2009
Posts: 1,257
Likes: 98
From: Ashland PA
2021 C4 of the Year - Modified Finalist
When I replaced my master cylinder and rebuilt the calibers the only way I was able to get all the air out of the system was to actuate the ABS while bleeding, THe a big burb of air came out the passenger side rear and all was fine.
Team Owner
Joined: Jul 2004
Posts: 28,378
Likes: 3,261
From: Hartford WI
How would you do that without some sort of tool like the Tech One, IIRC, to activate the ABS?
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Drifting
Joined: Jul 2009
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From: Ashland PA
2021 C4 of the Year - Modified Finalist
I did it in a way I do not recommend. I unpluged the ABS computer then ran power directly to the pin that activates the pump, I do not no if this activates any of the valves but when I bled the brakes with the pump running a big gulp of air came out, I then went and bled the rest of the calibers and the brake pedal has been solid since, I plugged the ABS back in took it for a ride and tried locking up the brakes and the ABS worked.
Drifting
Joined: Jul 2009
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From: Ashland PA
2021 C4 of the Year - Modified Finalist
Team Owner
Joined: Jul 2004
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From: Hartford WI
How? It only works when energized and how would you activate it except for a second or two? Why not get someone with the tools to do it instead of fudging it on your own? This is critical not trivia. Stopping is kinda important. Don't screw with my safety.
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Joined: Sep 2003
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From: Freedom is never more than one generation away from extinction.
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I unpluged the ABS computer then ran power directly to the pin that activates the pump, I do not no if this activates any of the valves but when I bled the brakes with the pump running a big gulp of air came out, I then went and bled the rest of the calibers and the brake pedal has been solid since
Seems like a reasonable problem solver.
Melting Slicks
Joined: Jan 2014
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From: Lunenburg MA
Team Owner
Joined: Jul 2004
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From: Hartford WI