Major brake issue!!! 1978 corvette
Thread Starter
Heel & Toe
Joined: May 2016
Posts: 18
Likes: 0
From: Atlanta Ga
Major brake issue!!! 1978 corvette
Hey forum, I recently installed a new master cylinder in my 'Vette. Fixed my sinking pedal. Bled the system, and i'm expecting to get out on the road and have fantastic brakes. (by the way i have new calipers on the back). But when i got to driving it on my street my braking was very poor. It'll roll for a little bit before finally coming to a complete stop, while at the same time my steering wheel will turn a substantial amount to the left. Could it be seized calipers? I really want to have my 'Vette back on the road but i just can't seem to figure out how to assess these issues. Any information ya'll could give me is greatly appreciated.
Thanks, Gary.
Thanks, Gary.
Le Mans Master
Joined: Sep 2002
Posts: 5,236
Likes: 898
From: Myrtle Beach SC
It sounds like you are performed three tasks here, calipers, master cylinder/ bleed brake system? But you write in such a way that it is not clear...so...
Is pedal going flat when you apply the brake? Or is there some pressure?
So did you only replace the master cylinder or did you replace calipers. You mention calipers but it's not clear if they were exchanged.
Did you bench bleed the master cylinder? If not you could have air in the system.
Did you bleed from right rear using recommended procedure?
Did you use DOT 3 or silicone? If you used silicone, the recommendation is to gravity bleed the system, which takes some time. Power bleeding agitates silicone and introduces air.
This would be quite disturbing assuming it did not turn left before your brake system work. If you replaced calipers, did you take them apart and made sure they were cleaned and lubricated before assembly and installation? If you replaced calipers, I would remove, take them apart and check them. Are the rubber seals lip seal or O ring style seal?
As you know, you do not want to drive with brakes that you are not confident will perfect as expected. Research the forum here and see if your procedure departed from recommendations for each of three tasks you performed.
In the end, I would bleed it again.
Is pedal going flat when you apply the brake? Or is there some pressure?
So did you only replace the master cylinder or did you replace calipers. You mention calipers but it's not clear if they were exchanged.
Did you bench bleed the master cylinder? If not you could have air in the system.
Did you bleed from right rear using recommended procedure?
Did you use DOT 3 or silicone? If you used silicone, the recommendation is to gravity bleed the system, which takes some time. Power bleeding agitates silicone and introduces air.
But when i got to driving it on my street my braking was very poor. It'll roll for a little bit before finally coming to a complete stop, while at the same time my steering wheel will turn a substantial amount to the left. Could it be seized calipers?
As you know, you do not want to drive with brakes that you are not confident will perfect as expected. Research the forum here and see if your procedure departed from recommendations for each of three tasks you performed.
In the end, I would bleed it again.
Last edited by hunt4cleanair; May 25, 2016 at 04:44 AM.
Melting Slicks
Joined: Mar 2008
Posts: 2,989
Likes: 198
From: Meriden CT
Inspect the front brakes, pay close attention to the right side. Air could be in that side or the rubber line could be blocked on that side. New rubber lines are cheap. Wheel bearings adjusted right?
Zen Vet Master Level VII
Joined: Mar 2016
Posts: 5,218
Likes: 1,174
From: Southlake, TX
Sounds like you have a bleeding issue to me. Start with a four corner bleed and see what happens.
You did a lot of good work so my guess is you have air in the system
You did a lot of good work so my guess is you have air in the system
Last edited by billschroeder5842; May 25, 2016 at 06:30 AM.
Racer
Joined: May 2011
Posts: 373
Likes: 6
From: Dover Delaware
Note for Bill S..
I am a fan of the gravity bleed procedure and not sure if I am doing it correctly..
Thanks Bill.....mk's78 aka Mike
Zen Vet Master Level VII
Joined: Mar 2016
Posts: 5,218
Likes: 1,174
From: Southlake, TX
You will need two people for this one... one to man the brake/bleeder screw and the other to pump the brake.
You will have your partner apply pressure to the brake and pump it. You will be at the brake and will wait until pressure is applied and then slowly loosen the bleeder screw.
You MAY see drips, splats and spurts-- that it normal as trapped air is escaping.
Loosen and tighten a few times while pumping until you get a steady stream of brake fluid-- that means that the system is free of air.
Now the "four corner" bleed is just the pattern you follow starting with the furthest brake from the master cylinder.
First- passenger rear
Second- drivers rear
Third- passenger front
Last- drivers front
Have a rag handy and wear safety goggles
Good luck!
You will have your partner apply pressure to the brake and pump it. You will be at the brake and will wait until pressure is applied and then slowly loosen the bleeder screw.
You MAY see drips, splats and spurts-- that it normal as trapped air is escaping.
Loosen and tighten a few times while pumping until you get a steady stream of brake fluid-- that means that the system is free of air.
Now the "four corner" bleed is just the pattern you follow starting with the furthest brake from the master cylinder.
First- passenger rear
Second- drivers rear
Third- passenger front
Last- drivers front
Have a rag handy and wear safety goggles
Good luck!
Thread Starter
Heel & Toe
Joined: May 2016
Posts: 18
Likes: 0
From: Atlanta Ga
Thanks for the replies you guys.
I have bled the master cylinder, and i bled my entire brake system using the "four corner" method. Prior to getting a new master cylinder i had problems with my brake pedal sinking straight to the floor, it no longer sinks like it did. And when i press the brakes when i'm going around 10-15 mph it rolls before finally grabbing and the steering wheel turns what seems like almost a 360 degree turn to the left. Everything has been bled appropriately, (even my emergency brake works now, it didn't before
)
secondly, the rear calipers were put on by a trusted brake technician i know. I'm rewording my message as the first one wasn't clear enough
Thanks, Gary.
I have bled the master cylinder, and i bled my entire brake system using the "four corner" method. Prior to getting a new master cylinder i had problems with my brake pedal sinking straight to the floor, it no longer sinks like it did. And when i press the brakes when i'm going around 10-15 mph it rolls before finally grabbing and the steering wheel turns what seems like almost a 360 degree turn to the left. Everything has been bled appropriately, (even my emergency brake works now, it didn't before
)secondly, the rear calipers were put on by a trusted brake technician i know. I'm rewording my message as the first one wasn't clear enough
Thanks, Gary.
Drifting
Joined: Jan 2012
Posts: 1,908
Likes: 129
From: Fredericksburg Virginia
What method did you use for your bleed? I have to agree with others...you may not think it's a bleeding thing, but it sure has all the symptoms of a bleeding thing.
I've run MASSIVE amounts of brake fluid through cars before getting all the bubbles out. It isn't one of those "I've cleared the line and that's it" sort of deals. I've run 1-1/2 large jugs of fluid through one line before. I used 3 large jugs last time I did my Corvette. Same for my Subaru. Both had crappy brakes before and AWESOME brakes now. Nothing but a really solid bleed.
I personally prefer the gravity bleed method, for what it's worth. Takes a while, but it's worth it.
I've run MASSIVE amounts of brake fluid through cars before getting all the bubbles out. It isn't one of those "I've cleared the line and that's it" sort of deals. I've run 1-1/2 large jugs of fluid through one line before. I used 3 large jugs last time I did my Corvette. Same for my Subaru. Both had crappy brakes before and AWESOME brakes now. Nothing but a really solid bleed.
I personally prefer the gravity bleed method, for what it's worth. Takes a while, but it's worth it.
Last edited by keithinspace; May 25, 2016 at 02:23 PM.
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Thread Starter
Heel & Toe
Joined: May 2016
Posts: 18
Likes: 0
From: Atlanta Ga
I had someone in the car pumping while i had a tube attached to my bleeder. We did all the lines until nothing but steady clean brake fluid was coming through. I wasn't aware that i had to put that much fluid through them.
Le Mans Master
Joined: Sep 2002
Posts: 5,236
Likes: 898
From: Myrtle Beach SC
Did the tube remain immersed in fluid during the bleeding operation?
Melting Slicks
Joined: Jan 2014
Posts: 2,478
Likes: 254
From: Downers Grove Illinois
The end of the tube sitting in the container should always be under fluid in the container or you can suck air back into the brake lines.
Thread Starter
Heel & Toe
Joined: May 2016
Posts: 18
Likes: 0
From: Atlanta Ga
Thanks, Gary.
Melting Slicks
Joined: Mar 2008
Posts: 2,989
Likes: 198
From: Meriden CT
Sure could. Inspect the bearings before simply adjusting them, might be damaged if it was real loose. If you replace them, replace the race along with them.
Last edited by SH-60B; May 25, 2016 at 05:19 PM.
Le Mans Master
Joined: Oct 2006
Posts: 8,941
Likes: 35
From: El Cajon California
I have a 78 and had the same problem...
If you need to bleed the calipers the Corvette is a different than any other car I have ever worked on...
You need to bleed the brakes in the following fashion...
Left rear inner
Left rear outer
Right rear inner
Right rear outer
Left front
Right front
If you need to bleed the calipers the Corvette is a different than any other car I have ever worked on...
You need to bleed the brakes in the following fashion...
Left rear inner
Left rear outer
Right rear inner
Right rear outer
Left front
Right front
Last edited by Snoopysvet; May 26, 2016 at 01:03 PM.
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
with keith
When you think you got the air out keep going that gets you a great pedal
Look into speedbleeders, gods gift to the one man bleed job.
Love those things cant screw it up.
Summit sells them.
When you think you got the air out keep going that gets you a great pedal
Look into speedbleeders, gods gift to the one man bleed job.
Love those things cant screw it up.
Summit sells them.