Brake Issue
Thread Starter
Instructor
Joined: Apr 2011
Posts: 154
Likes: 0
From: Grand Haven Michigan
Brake Issue
A few weeks ago I went to take the '71 for a cruise and realized my foot went to the floor and I was barely stopping. Checked the brake fluid levels and found the rear to be almost empty. In the garage, a puddle where the rear passenger side tire is.
Now, that caliper has been rebuilt, pads replaced on all the brakes. I had to remove the brake line on the front to replace the pads. Bleed them once with my wife's help, and again with a vacuum bleeder. Got in the car, pumped the brake pedal and it felt good. Start the car and all of a sudden it seemed like I had no brakes again.
Any ideas on what is going on?
Thanks,
Jay
Now, that caliper has been rebuilt, pads replaced on all the brakes. I had to remove the brake line on the front to replace the pads. Bleed them once with my wife's help, and again with a vacuum bleeder. Got in the car, pumped the brake pedal and it felt good. Start the car and all of a sudden it seemed like I had no brakes again.
Any ideas on what is going on?
Thanks,
Jay
Drifting
Joined: Aug 2005
Posts: 1,372
Likes: 4
From: Springfield VA
^ Yep
That and lip seals, from what others hear have said, do not work well when vacuum bleeder was used. The vacuum bleeder can pull in air from wheels you have already bleed.
When doing major work on the brakes I first gravity bleed and then pump the peddle bleed.
That and lip seals, from what others hear have said, do not work well when vacuum bleeder was used. The vacuum bleeder can pull in air from wheels you have already bleed.
When doing major work on the brakes I first gravity bleed and then pump the peddle bleed.
Race Director
Joined: Apr 2011
Posts: 11,183
Likes: 3,333
From: North of Toronto - Ontario
Personally not a fan of vac-bleeders on the lip-style calipers. They can actually suck air into the caliper (the lip seals are made to flair out and prevent fluid from going by in the "out" direction, virtually no seal going the other way (air)
Chances are when the caliper leaked in the first place it may have emptied the master and there is air way up in the system somewhere.
Gravity bleed (I've never done but there are lots of threads on) or pressure bleed (I use a motive bleeder) the entire system (all 4 wheels) or have your wife help again and do lots of tries to make sure any air trapped high in the system gets all the way to a caliper.
My .02, actual mileage may vary, results not typical...
Mooser
Chances are when the caliper leaked in the first place it may have emptied the master and there is air way up in the system somewhere.
Gravity bleed (I've never done but there are lots of threads on) or pressure bleed (I use a motive bleeder) the entire system (all 4 wheels) or have your wife help again and do lots of tries to make sure any air trapped high in the system gets all the way to a caliper.
My .02, actual mileage may vary, results not typical...
Mooser
Thread Starter
Instructor
Joined: Apr 2011
Posts: 154
Likes: 0
From: Grand Haven Michigan
would using the vacuum pump to get the fluid started at the caliper be at least a good start?
I will switch to the 2 person method next.
Another question, the back caliper has 3 bleeder valves, one on the inner side and 2 on the outer side, do I have to bleed out of all 3, and in what order?
this is the vacuum system that I am currently borrowing:
Mityvac MV8000 Brake Bleeding Kit
I will switch to the 2 person method next.
Another question, the back caliper has 3 bleeder valves, one on the inner side and 2 on the outer side, do I have to bleed out of all 3, and in what order?
this is the vacuum system that I am currently borrowing:
Mityvac MV8000 Brake Bleeding Kit
Race Director
Joined: Aug 1999
Posts: 18,126
Likes: 174
From: WI
in the rear you only bleed the bleed screws facing forward, that third one you don`t need to touch, it came from the factory (and if rebuilt by a competent rebuilder) would have come with a plug. If it was me I think I would have rebuilt all 4 calipers and certainly would have changed all 16 pistons.
Melting Slicks
Joined: Aug 2005
Posts: 2,683
Likes: 34
From: Working on the car NY
Thanks for the info. While I rarely use the vacumn bleeder, I didn't know this info. I have a Motive bleeder but actually now prefer the (old fashioned) 2 person bleed method.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
2027 Corvette vs The World: Every Model vs Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
5 MOST and 5 LEAST Popular Corvette Model Years in History!
Joe Kucinski
2027 Corvette Buyer's Guide: Everything You Need to Know!
Joe Kucinski
10 Things C8 Corvette Owners Hate (But Won't Tell You)
Joe Kucinski
10 Best Corvettes Coming to Barrett-Jackson Palm Beach 2026!
Brett Foote
Every Corvette Grand Sport Explained! (C2, C4, C6, C7, & C8)
Joe Kucinski
Grand Sport & Grand Sport X Launch Alongside All-New 535hp LS6 V8!
Michael S. Palmer
5 Reasons Bad Drivers Crash & 5 Ways to Avoid a Costly Mistake!
Joe Kucinski
Thread Starter
Instructor
Joined: Apr 2011
Posts: 154
Likes: 0
From: Grand Haven Michigan
Just a small update, I have gone through bleeding the brakes with gravity and then the 2 person method just to be sure. Car off I have good brakes, peddle almost doesn't move.
But when I turn the car on its like the brakes are slow to respond. What I am curious is if the power brakes is the factor now. Before I did some caliper work the brakes were always slow, but now that I am started I want to get things right.
I was looking things over last night and noticed the vacuum line going to the power brakes is connected to a tee junction on the intake manifold just below the carburetor. The intake and carburetor are aftermarket installed by previous owner. I am not sure if these hoses got hooked up right. I will check the AIM tonight and the user manual for the carb, but just wondering if I am barking up the right tree.
Pic of the hoses:
Thanks,
Jay
But when I turn the car on its like the brakes are slow to respond. What I am curious is if the power brakes is the factor now. Before I did some caliper work the brakes were always slow, but now that I am started I want to get things right.
I was looking things over last night and noticed the vacuum line going to the power brakes is connected to a tee junction on the intake manifold just below the carburetor. The intake and carburetor are aftermarket installed by previous owner. I am not sure if these hoses got hooked up right. I will check the AIM tonight and the user manual for the carb, but just wondering if I am barking up the right tree.
Pic of the hoses:
Thanks,
Jay
Drifting
Joined: May 2008
Posts: 1,647
Likes: 5
From: Roseville CA
Sounds like a booster issue. If you're lucky, it's just the hose or check valve. You should get 1 - 3 powered pumps after you turn the engine off. Even after waiting a few minutes. You could test with a mighty vac too. I had similar symptoms on my 71 and could not pull any vacuum using the might vac. Bought a rebuilt one from O'Reillys and could get vacuum starting at about 10 pumps. After replacing the booster, the brakes are amazing! Bitch of a job though.
Thread Starter
Instructor
Joined: Apr 2011
Posts: 154
Likes: 0
From: Grand Haven Michigan
Well, problem is solved for now. I hooked a vacuum gauge on the car and noticed that with nothing but the gauge it fluctuated from 5 to 14 on the gauge. After finding the vacuum diagnostic chart on wilcox corvette site I realized that I might have a misfire issue. Replaced all the spark plugs and wires, checked vacuum again, had a small fluctuation from 14-16, but not as severe and the brakes were much better. Not to mention the car actually sounding and responding better as well.
Thanks for all the advice on the brakes, turned out my car had more then just a brake problem in the end!
Thanks for all the advice on the brakes, turned out my car had more then just a brake problem in the end!
Thread Starter
Instructor
Joined: Apr 2011
Posts: 154
Likes: 0
From: Grand Haven Michigan
Ok... so I got excited too fast, brakes are great now. went home on lunch, fuse to the radio fell out so i fixed it temporarily till winter when I plan to redo the wiring. Start the car a couple times to make sure it works. Get out and see a nice giant puddle of anti freeze on the ground...
open the hood and there is a big puddle on the intake on the front drivers side. With smaller puddles all the way back on the drivers side. Passenger side is clean. Will check total level of coolant when I get home tonight, pretty sure its going to be low...
Any ideas on where to start looking?
Thanks,
Jay
open the hood and there is a big puddle on the intake on the front drivers side. With smaller puddles all the way back on the drivers side. Passenger side is clean. Will check total level of coolant when I get home tonight, pretty sure its going to be low...
Any ideas on where to start looking?
Thanks,
Jay
Race Director
Joined: Apr 2011
Posts: 11,183
Likes: 3,333
From: North of Toronto - Ontario
Should start a new thread
But in the meantime, wipe everything down and check the hose to waterneck and waterneck to intake manifold joints. If it leaked there it will get blown back along the drivers side by the fan.
Start the car, let it come to temp so the thermostat opens and watch for your leak
Mooser
But in the meantime, wipe everything down and check the hose to waterneck and waterneck to intake manifold joints. If it leaked there it will get blown back along the drivers side by the fan.
Start the car, let it come to temp so the thermostat opens and watch for your leak
Mooser