CPP Rear Disc Brakes not bleeding!!

[Jason Banks]

I know you said it's all new and you are getting fluid at the caliper. But, since I cant see it in your pictures I'll throw this out. The rubber line between the frame and rear end is many times plugged not allowing enough fluid to the rear brakes.

[Tx70Gmc]

Originally Posted by Jason Banks

I know you said it's all new and you are getting fluid at the caliper. But, since I cant see it in your pictures I'll throw this out. The rubber line between the frame and rear end is many times plugged not allowing enough fluid to the rear brakes.

The rubber lines are brand new from the kit and they have fluid coming out of them.
Which is why its weird the calipers arent working

[Jason Banks]

I looked through the CPP kits and it doesn't look like the rubber line that I'm talking about is included in any of the kits.


I'm talking about the one that goes from the frame to the rear end.


The CPP kits look like they include hard lines that connect to the TEE at the end of the hose I'm talking about and it looks like they include the rubber lines to go to the calipers.

[leddzepp]

Originally Posted by Tx70Gmc

The rubber lines are brand new from the kit and they have fluid coming out of them.
Which is why its weird the calipers arent working

If the rubber line at the frame is old there is a strong possibility that it swells up when your brake pedal is pressed and there isn’t enough fluid or pressure to operate the calipers.

[Chevy nutcase]

I had the exact same problem on my 66 when I replaced everything including a new dual reservoir master cylinder. The front brakes bled instantly but even with a friend pumping I couldn't get a drop to the rear brakes. Bench bled it a second time and still nothing. I only had one idea to let gravity help so I opened the rear bleeders and disconnected the hardline from the master cylinder. Luckily I had a length of clear tubing big enough to fit tightly over the flared end of the line I removed from the master cylinder. I then filled a bottle that resembled a ketchup bottle with brake fluid, stuck the hose to it and hung it from my open hood like an IV bottle. It took a minute or two till it started running out of the bleeders but I then closed the bleeders and hooked the line back to the master cylinder and voila I was able to bleed out the remaining air bubbles like normal. Sounds janky but it worked.

[Tx70Gmc]

Originally Posted by Jason Banks

I looked through the CPP kits and it doesn't look like the rubber line that I'm talking about is included in any of the kits.


I'm talking about the one that goes from the frame to the rear end.


The CPP kits look like they include hard lines that connect to the TEE at the end of the hose I'm talking about and it looks like they include the rubber lines to go to the calipers.

Okay, i know what rubber hose you are talking about.
Ill replace it, but i am getting fluid to the rear brakes, so i think it is working properly

[LS short box]

Having a LS engine would make no difference.
I would try a Mity Vac vacuum bleeder or a Motive pressure bleeder. I think some of the parts stores have loaner tools. Check with them.
Back in the day I made a pressure bleeder. I took a piece of 1/4" steel flat stock sized a bit bigger than MC cover. Drilled and tapped two 1/8" NPT holes in the steel plate. Then I screwed in two 1/8" nipples. Then using rubber hoses connected the two nipples to a "T" to a single piece of rubber hose with a air hose fitting. On the under side of the plate I glued a piece of inner tube to seal it to the MC. I used a couple of c-clamps to clamp it to the top of the MC. Ran about 30-40 PSI. Worked great. You just have to refill the master as you bleed.

[Jason Banks]

I have one of these that I always use when bleeding a new system.

https://www.harborfreight.com/brake-...der-92924.html

I don't use the bottle, just the vacuum part.

I revert back to pumping the pedal and the one-man bleeder bottle for the final bleed.

[Tx70Gmc]

Originally Posted by LS short box

Having a LS engine would make no difference.
I would try a Mity Vac vacuum bleeder or a Motive pressure bleeder. I think some of the parts stores have loaner tools. Check with them.
Back in the day I made a pressure bleeder. I took a piece of 1/4" steel flat stock sized a bit bigger than MC cover. Drilled and tapped two 1/8" NPT holes in the steel plate. Then I screwed in two 1/8" nipples. Then using rubber hoses connected the two nipples to a "T" to a single piece of rubber hose with a air hose fitting. On the under side of the plate I glued a piece of inner tube to seal it to the MC. I used a couple of c-clamps to clamp it to the top of the MC. Ran about 30-40 PSI. Worked great. You just have to refill the master as you bleed.

Having an LS would make difference in what....bleeding?

[Tx70Gmc]

Originally Posted by Jason Banks

I have one of these that I always use when bleeding a new system.

https://www.harborfreight.com/brake-...der-92924.html

I don't use the bottle, just the vacuum part.

I revert back to pumping the pedal and the one-man bleeder bottle for the final bleed.

I have tried to use (rent) a vaccum bleeder without success.

[Tx70Gmc]

Originally Posted by Jason Banks

I looked through the CPP kits and it doesn't look like the rubber line that I'm talking about is included in any of the kits.


I'm talking about the one that goes from the frame to the rear end.


The CPP kits look like they include hard lines that connect to the TEE at the end of the hose I'm talking about and it looks like they include the rubber lines to go to the calipers.

Is this hose you are talking about?
Will it work with disc brakes or is there another hose i need to purchase for disc brakes?

[Jason Banks]

Where in Dallas are you? I'll loan you my harbor freight one...

Here's an example of the hose. It doesn't matter if disc or drum, it's just passing fluid from the hard line on the frame to the hard lines on the rear differential.

https://www.classicparts.com/1967-70...ctinfo/71-361/

Here's another...
https://www.rockauto.com/en/moreinfo...t=1792&jsn=937

And another
https://www.oreillyauto.com/detail/c...ckup-rwd?pos=1

[Tx70Gmc]

Originally Posted by Jason Banks

Where in Dallas are you? I'll loan you my harbor freight one...

Here's an example of the hose. It doesn't matter if disc or drum, it's just passing fluid from the hard line on the frame to the hard lines on the rear differential.

https://www.classicparts.com/1967-70...ctinfo/71-361/

Here's another...
https://www.rockauto.com/en/moreinfo...t=1792&jsn=937

And another
https://www.oreillyauto.com/detail/c...ckup-rwd?pos=1

Those do not work with my setup.
I have a union that connects the hard lines on either side of the gear on the axle cover.

https://www.summitracing.com/parts/d...RoCbWwQAvD_BwE

This is what i have on my setup from the frame hardline to the axle hardlines

[Jason Banks]

Ok, I thought your truck was a 70? I think the one with the "TEE" built in is 71-72...

https://www.classicparts.com/1971-72...ctinfo/71-365/

Either way, if that line is original, you want to replace it.

[Jason Banks]

Here's the "TEE" that goes on the other line style...

https://www.classicparts.com/38-70-T...ctinfo/71-882/

[Jason Banks]

Crap, here's another question... Is your truck leaf or coils spring rear? because there are different hoses...

[Tx70Gmc]

Originally Posted by Jason Banks

Crap, here's another question... Is your truck leaf or coils spring rear? because there are different hoses...

It is coil springs and a 1970 GMC LWB...if that matters

[72c20customcamper]

Are you getting pressure at the caliper line or just a little fluid ? You followed these instructions to set the ebrake? I had a problem with the 79 Caddy calipers on my Chevelle I had adjust the ebrake a few times

Mine came from the Right Stuff Detailing but the procedure is the same as yours since it's a gm caliper
https://youtu.be/mlGt61_Sdb0

[Truckin Fool]

I’m not sure if this is the problem but I had a similar problem with a classic Mustang front disc conversion some time ago. The brake calipers would not bleed. If you cracked the line at the calipers they would split fluid all over the place. The problem ended up being that the new caliper pistons had a very small radius on the bottom and Ford had a very large radius on their pistons. The hole that came into the bore was at the very bottom of the bore but came in from the side and not the bottom. When the piston was fully in to the bottom of the bore it would completely block off the hole. We sent the pistons out the a machine shop and had them add a larger radius to the piston and that solved the problem. I know it sounds stupid but sometimes stupid stuff happens. Just as a note , we had performed hundreds of conversions using the same kit and never had a problem. Dan.

[03BlkZ]

Just a suggestion and I admit I didn't read the entire post but make sure you have them installed on the correct side. The bleeder needs to be at the top. I make a stupid mistake on my CPP front brakes and installed them on the wrong side and bleeder was down. I fought it for a few weeks not understanding why I had soft brakes then one day I looked at it and saw it. I was like crap seriously. I swapped them and brakes have been perfect ever since.

[Tx70Gmc]

Originally Posted by 72c20customcamper

Are you getting pressure at the caliper line or just a little fluid ? You followed these instructions to set the ebrake? I had a problem with the 79 Caddy calipers on my Chevelle I had adjust the ebrake a few times

Mine came from the Right Stuff Detailing but the procedure is the same as yours since it's a gm caliper
https://youtu.be/mlGt61_Sdb0

Thanks for the video, i have the ebrake adjusted and working great.
I am not getting any pressure at the caliper when i press the brake pedal.

[Tx70Gmc]

Originally Posted by Truckin Fool

I’m not sure if this is the problem but I had a similar problem with a classic Mustang front disc conversion some time ago. The brake calipers would not bleed. If you cracked the line at the calipers they would split fluid all over the place. The problem ended up being that the new caliper pistons had a very small radius on the bottom and Ford had a very large radius on their pistons. The hole that came into the bore was at the very bottom of the bore but came in from the side and not the bottom. When the piston was fully in to the bottom of the bore it would completely block off the hole. We sent the pistons out the a machine shop and had them add a larger radius to the piston and that solved the problem. I know it sounds stupid but sometimes stupid stuff happens. Just as a note , we had performed hundreds of conversions using the same kit and never had a problem. Dan.

Maybe that is my problem?
I emailed CPP to see if i could exchange these for a new set and im waiting to hear back. The only thing i can think of is these calipers are defective.

[PbFut]

Originally Posted by Tx70Gmc

I am not getting any pressure at the caliper when i press the brake pedal.

To confirm:
1. No pressure at the bleeder nipple on the caliper
2. Pressure/Fluid at the connector of the break line to caliper. (2 calipers per circuit)

If so....you are not getting enough pressure to move the caliper piston past the bleeder port or the caliper is defective. Odd both calipers would be given you have a front and rear circuit. Is it possible that you still have air in the system? If so, opening the connection at the break line and caliper would result in you being able to push fluid out with the brake pedal and no real pressure would be required. But....if there is air in the system up stream, then the air pocket(s) might be enough to compress and eliminate or greatly reduce the pressure at the caliper piston when connected. Whereby not being sufficient pressure to move the caliper to a position the bleeder port is exposed.

Maybe as a test...Remove break line at the caliper. Use DRY compressed air and pressurize the caliper at the break line port of the caliper. Open the bleeder nipple. If you get any air then the caliper is ok and you need to look to other parts of the system.

Everyone has their preference. I have always used a vacuum bleeder with excellent results. On occasion a few pumps of the peddle was all I needed to get any pesky bubbles to clear and be vacuumed out.

Best of luck. This can be a frustrating process but I am betting it is probably air in the system.

[Joyridin]

Anything on this? Just curious as to the outcome.

[Tx70Gmc]

Originally Posted by PbFut

To confirm:
1. No pressure at the bleeder nipple on the caliper
2. Pressure/Fluid at the connector of the break line to caliper. (2 calipers per circuit)

If so....you are not getting enough pressure to move the caliper piston past the bleeder port or the caliper is defective. Odd both calipers would be given you have a front and rear circuit. Is it possible that you still have air in the system? If so, opening the connection at the break line and caliper would result in you being able to push fluid out with the brake pedal and no real pressure would be required. But....if there is air in the system up stream, then the air pocket(s) might be enough to compress and eliminate or greatly reduce the pressure at the caliper piston when connected. Whereby not being sufficient pressure to move the caliper to a position the bleeder port is exposed.

Maybe as a test...Remove break line at the caliper. Use DRY compressed air and pressurize the caliper at the break line port of the caliper. Open the bleeder nipple. If you get any air then the caliper is ok and you need to look to other parts of the system.

Everyone has their preference. I have always used a vacuum bleeder with excellent results. On occasion a few pumps of the peddle was all I needed to get any pesky bubbles to clear and be vacuumed out.

Best of luck. This can be a frustrating process but I am betting it is probably air in the system.

I have removed the flex brakeline from the calipers and used compressed air to blow thru the caliper and out the bleeder with success.

However i still cant get fluid to the bleeder.