so, I have been working on doing a full disc brake swap on a 1972 base car that was formally all drum brakes. I have completely swapped everything out for new from the MC to the lines and I cannot get brakes. I have adjusted the pedal out and in with no change. All the parts were brand new, and I have done my best to follow all instructions. I just can't figure this out no matter what I do the pedal stays hard and when you bleed them out it has no pressure whatsoever. if anyone has any ideas what I could be doing wrong, please let me know I am pulling my hair out at this point.
4 wheel disc conversion help
wreckerguy85
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so, I have been working on doing a full disc brake swap on a 1972 base car that was formally all drum brakes. I have completely swapped everything out for new from the MC to the lines and I cannot get brakes. I have adjusted the pedal out and in with no change. All the parts were brand new, and I have done my best to follow all instructions. I just can't figure this out no matter what I do the pedal stays hard and when you bleed them out it has no pressure whatsoever. if anyone has any ideas what I could be doing wrong, please let me know I am pulling my hair out at this point.
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Yes have bench bled it 2-3 times I have tried everything bleeding them from the ol fashion pump method (with help) to using a vacuum bleeder there is no air in the system
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Prop. Valve is brand new as well and as far as I can tell it's not off center I have tried it both ways from the pv to a "t" then to each caliper that didn't work so I have since run independent lines to both calipers out of the pv it feels like the whole travel on the pedal is about 2" it doesn't move much at all and is much harder than any pedal I have ever pressed
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Checked and adjusted both all of this was purchased together new from one of the big proformence sites it was all recommended to work together the said there should be less than 1/4 in between the booster rod and the mc
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7,704 Posts
The ebrake adjustment plays a major part in some brands of disc brakes.
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The ebrake doesn't actually work the pedal assembly is broken so it's not hooked up at all
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277 Posts
I had a similar problem. Make sure you are using the littler screw in tool to keep the shuttle valve centered while bleeding.
Also, you will need to size the correct MC to your system. I was using a 7/8" bore MC and the pedal would never get stiff.... I would then move to a 1 1/8" bore MC and now my pedal is stiff.
Bench bleeding is important. Just set it up in your bench vise, hook up hoses, fill up the reservoir with fluid and push on the cylinder til no more air.
Also, behind the MC next to the booster you might have a stud that pushes into the MC, it needs to be the correct length, in general you want full travel of the MC and full travel of the pedal that isn't impeded by the floor.
Also, you will need to size the correct MC to your system. I was using a 7/8" bore MC and the pedal would never get stiff.... I would then move to a 1 1/8" bore MC and now my pedal is stiff.
Bench bleeding is important. Just set it up in your bench vise, hook up hoses, fill up the reservoir with fluid and push on the cylinder til no more air.
Also, behind the MC next to the booster you might have a stud that pushes into the MC, it needs to be the correct length, in general you want full travel of the MC and full travel of the pedal that isn't impeded by the floor.
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7,704 Posts
Again, the Ebrake adjustment affects the operation with some disc brake systems. You need to see how this applies to yours.
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I honestly think the MC is too small I have tried every adjustment possible I have bench bled it with the included hoses and have done it twice more on the car the pedal is always super hard engine running or off and it just has no pressure hardly. My pv does not have any kind of adjustment on it just the 3 connections the electrical connection and the bolt holes so I'm not sure what you mean by the tool for the shuttle valve there isn't anyway that I know of to hold it centered
Hook up the electrical connection to your brake dash light, use an ohm meter, or a test light to see if that connection is grounded. If it is, the PV is off center and will block fluid flow to the front or back lines. This is a safety feature incase you have a leak. They make a tool to hold it centered while you bleed the brakes.
Amazon.com: Brake Proportioning Valve Bleeder Tool, Valve Bleeding Tool Compatible with GM Combination Valves, PV2 PV4, Disc/Disc Disc/Drum 172-1353 172-1371 (Blue) : Automotive
Buy Brake Proportioning Valve Bleeder Tool, Valve Bleeding Tool Compatible with GM Combination Valves, PV2 PV4, Disc/Disc Disc/Drum 172-1353 172-1371 (Blue): Proportioning Valves - Amazon.com âś“ FREE DELIVERY possible on eligible purchases
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Bleed Your Brakes Easily | Master Power Brakes
To bleed your brakes is necessary to ensure all air bubbles are removed from the system. Let’s do a quick overview of the brake-bleeding process.
mpbrakes.com
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I will definitely check this out thank youHook up the electrical connection to your brake dash light, use an ohm meter, or a test light to see if that connection is grounded. If it is, the PV is off center and will block fluid flow to the front or back lines. This is a safety feature incase you have a leak. They make a tool to hold it centered while you bleed the brakes.
Amazon.com: Brake Proportioning Valve Bleeder Tool, Valve Bleeding Tool Compatible with GM Combination Valves, PV2 PV4, Disc/Disc Disc/Drum 172-1353 172-1371 (Blue) : Automotive
Buy Brake Proportioning Valve Bleeder Tool, Valve Bleeding Tool Compatible with GM Combination Valves, PV2 PV4, Disc/Disc Disc/Drum 172-1353 172-1371 (Blue): Proportioning Valves - Amazon.com âś“ FREE DELIVERY possible on eligible purchaseswww.amazon.com
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I will check this in the morning and update ASAP
Dear WreckerGuy85, I have recently Updated My Team Chevelle Rear Disc Conversion Post. Please Look at this Post as is May Help You Solve Your Problem especially with Master Cylinder Bore Sizes. I do agree with Old Cutlass that Your Parking Brake needs to be working and Adjusted Properly for Your Brake Pedal to Work Correctly. On this Post there are 2 You Tube Videos showing how the Cadillac Seville Eldorado Rear Disc Brake Works so You can Fix Your E Brake. The First Video Below start at 7 Minutes (Do Not Take You New Caliper Apart) just watch how the E Brake Adjustment is Made on the Bench. I Wish You Much Success. Sincerely Gary 396
https://www.chevelles.com/threads/1...velle-rear-disc-brake-conversion-or-11-inch-rear-brake-drum-conversion.1163204/
Excellent #1 You Tube Cadillac Seville Eldorado Rear Brake Adjustment " No Removal of Adjustment Lever"
Excellent #2 You Tube Cadillac Seville Eldorado "Rear Brake Lever Adjustment Lever Removal"
www.youtube.com
Excellent #3 CPP Video Cadillac Seville Rear Brake "See 6.20 Minute New Style 12 Point Adjustment Lever"
www.youtube.com
You Tube Old Master Brake Cadillac Seville Eldorado Rear Disc Brake Installation Video
You Tube Video On Difficult Cadillac Seville Eldorado Rear Disc Park Brake Adjustment for 1970 Chevelle
Start at 7 Minutes in Video to Adjust New Caliper. Do Not Take Your New Caliper Apart.
https://www.chevelles.com/threads/1...velle-rear-disc-brake-conversion-or-11-inch-rear-brake-drum-conversion.1163204/
Excellent #1 You Tube Cadillac Seville Eldorado Rear Brake Adjustment " No Removal of Adjustment Lever"
Excellent #2 You Tube Cadillac Seville Eldorado "Rear Brake Lever Adjustment Lever Removal"
- YouTube
Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on YouTube.
www.youtube.com
Excellent #3 CPP Video Cadillac Seville Rear Brake "See 6.20 Minute New Style 12 Point Adjustment Lever"
How To Adjust The Parking Brake On a Cadillac Style Caliper
Whether you are installing your new disc brake system for the first time or having issues with a low pedal, this video is for you! -Download the Disc Brake &...
www.youtube.com
You Tube Old Master Brake Cadillac Seville Eldorado Rear Disc Brake Installation Video
You Tube Video On Difficult Cadillac Seville Eldorado Rear Disc Park Brake Adjustment for 1970 Chevelle
Start at 7 Minutes in Video to Adjust New Caliper. Do Not Take Your New Caliper Apart.
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3,453 Posts
Get a brake pressure gauge and screw it into your calipers to see what fluid pressure you are getting to the caliper. If your pressure is correct then it has nothing to do with the master cylinder or brake light switch. You are generally looking for about 1550 to 1600 psi. With a pressure gauge it should be an easy diagnosis.
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