No pedal to rear brakes

Tiny
RALPH BJORNSON
  • MEMBER
  • 1961 CHEVROLET 3500
  • 5.4L
  • V8
  • 2WD
  • MANUAL
  • 10 MILES
Installed new disc brakes front, a new 1 inch bore dual master cylinder with power boost, under floor mount master cylinder, new brake pads and calipers for the rear. Bled the brakes, front work fine, bled the rear, no pedal and when trying to pump up the rear, pedal becomes real spongy. I have 2 pond residual pressure vales on front and rear, I have used air to blow out all lines before bleeding the system. I blocked of the master cylinder and stepped on the pedal, good and solid, I blocked off the rear to check the front, good brake pedal, blocked off the front and no pedal to the rear, I open the connection fitting on top of the third member rear end housing being the highest spot to check for air, all was good.I have used about 2 quarts of brake fluid.
Friday, September 10th, 2021 AT 8:42 PM

11 Replies

Tiny
KASEKENNY
  • MECHANIC
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I just want to make sure I understand the issue. Your pedal goes to the floor and you have narrowed it to the rear brakes. You have blocked off the master cylinder and have a hard pedal. When you put the rear back in you have a soft pedal?

If this is the case then we have to continue to narrow it down because you have only two ports coming from this master, correct? We don't have a manual on this so I am going to have to rely on you to tell me how it is set up. Is it split front and rear or is diagonally split?

Here is a guide that will help with this issue:

https://www.2carpros.com/articles/brake-pedal-goes-to-the-floor

Basically what is causing this is a leak or air in the lines. So if you are running this much fluid through the system and do not have air in the system because you are getting fluid out of the rear on both sides then we have a leak. It may be an internal leak that basically is just not holding the fluid pressure like it should so the pressure is bleeding off allowing the pedal to drop.

Any brake system requires it to be sealed so that all the pedal force is delivered to the back of the piston in the caliper. When there is a leak then that pressure bleeds off and the pedal drops.

Next thing I would do is use vice grips and pinch off both brake lines at the rear calipers as you should have rubber lines back there. If the pedal is hard or harder, then you have confirmed the system from the master to those vice grips is good. Then remove one at a time to see which side the issue is on. Just make sure you test both sides because while it is unlikely, you may have an issue with both rear calipers.

Please let us know what questions you have on this and we can go from there. Thanks
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Saturday, September 11th, 2021 AT 7:32 AM
Tiny
RALPH BJORNSON
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Hello KASEKENNY1, update on what I have done on my brake pedal goes to the floor. I blocked off a part of the old brake line to the rear calipers, found the portion of brake line was letting the pedal go to the floor. I replaced this with new 1/4 inch brake line, this is connected to the rear end. I tested this new brake line and have great brake pedal. When I connected the new lines to the rear end fittings after bleeding both rear calipers, the pedal still goes to the floor. These are brand new calipers and top of the line brake pads. I removed each caliper, made sure all moving parts had proper grease for disc brake. I put the calipers back on. I stopped at this point and will start again this morning. And send you an update. The really appreciate the information and guidance you posted for my challenge, this has been very helpful, thank you.
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Sunday, September 12th, 2021 AT 7:24 AM
Tiny
KASEKENNY
  • MECHANIC
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That is great info. So it sounds like when the calipers are connected is when you have the issue?

Basically if you replaced that line and checked it to that point and have a hard pedal, it is just a matter of continuing to move back until you find the issue.

One thing I would suggest is to no jump around. Just work backwards until the pedal is soft and you will find the issue.

Thanks for the update. Let us know how you make out.
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Sunday, September 12th, 2021 AT 8:30 AM
Tiny
RALPH BJORNSON
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  • 7 POSTS
Hi KASEKENNY 1, this morning I continued my quest and after blocking every possible fitting. I narrowed it down to the right rear brake caliper, I have another on order, should be here around 4:00 pm pacific standard time and install. Find out then. Thank you again.
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Sunday, September 12th, 2021 AT 2:30 PM
Tiny
RALPH BJORNSON
  • MEMBER
  • 7 POSTS
Hi KASEKENNY 1, I installed the new disc brake caliper, bled the caliper, stepped on the pedal and it went right to the floor and pumping up the pedal is very spongy. All indications and testing went to this area. Is there something I missed or what? Thank you for looking at this problem.
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Sunday, September 12th, 2021 AT 6:19 PM
Tiny
KASEKENNY
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Wow. It is unlikely but it is possible that you have another new part that is faulty. What will tell us this is how you narrowed it down to this caliper.

I am not able to find what style fitting you have on the brake line that goes into the caliper. However, what I would do is remove the line from only this caliper and cap the line. This way the only thing not in the system is this caliper.

I attached a picture of a standard cap below that should work on all except the lines that have the banjo bolt.

Basically all you are doing is confirming that you have a hard pedal with everything but this caliper. If that is the case, then the source you are getting these from has a batch of faulty parts. Unfortunately this does happen.

However, I would not try to move on until you confirm it is still soft with this removed because I don't see what you are missing.
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Monday, September 13th, 2021 AT 7:55 AM
Tiny
RALPH BJORNSON
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  • 7 POSTS
Hello KaseKenny1, for the brake flued line fitting to the caliper is a banjo style, I cut 2 pieces of rubber a little larger than the banjo fitting and used a C clap to seal the fitting. It worked. I did notice as I worked from different fittings going away from the master cylinder the brake pedal would go closer to the floor. When I did the fitting at the caliper the pedal was firm but about 1 or 2 inches from the floor. This caliper was the 2nd new caliper so this would be the 3ard caliper I put on this side. I was wondering if the master cylinder is not large enough? This is a flat bed truck with dual wheels, a 1939 Chevrolet or would a 2lb residual valve work installed between the brake caliper and T fitting for the rear brake fluid slits between the 2 calipers?
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Monday, September 13th, 2021 AT 10:45 AM
Tiny
RALPH BJORNSON
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Hello KASEKENNY 1, I tried putting another 2 lb residual valve back by the rear calipers, all that did was made the calipers not release fully and the brakes where dragging. Not sure what to try next.
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Monday, September 13th, 2021 AT 3:10 PM
Tiny
KASEKENNY
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So if the master was not large enough you would not have much braking power as it would not apply the brakes very well but it would still have a hard pedal.

So lets try and cap that caliper a different way just to see what result we get.

As you can see below the banjo bolt has a hole that allows the fluid through when you press the brake. Just find a bolt from a hardware store that is the same length and install that banjo line on the caliper with it.

This will block the fluid from going any further then that line.

By doing it the way you did, it will not get a hard pedal until it fills that void so that make sense that it would be low.

This will be a definitive way to check this because I just can't believe this is anything other then that caliper.

If not then clearly we are missing something in the lines because if you capped the master and the pedal is hard then obviously we are missing it.
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Monday, September 13th, 2021 AT 6:35 PM
Tiny
RALPH BJORNSON
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Hello KaseKenny1, I did cap the banjo fitting using 2 pieces of rubber over the holes and a C clamp this worked. However the pedal was close to the floor about 1 to 2 inches from the floor but firm. I tried putting in another reserve valve 2lb close to the caliper. This made the rear brakes drag.
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Monday, September 13th, 2021 AT 7:50 PM
Tiny
KASEKENNY
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Understood. Are you getting fluid out of this caliper? Steady stream with good pressure when you open the bleeder?

Maybe get a video of this when you open the bleeder and that will help narrow this down.

The 2 lb valve is just to hold more pressure on the "south" side of it which is why they are dragging.

The pedal going to the floor is caused only by a lack of pressure being held in the system either because there is air in the line or the pressure is getting bled off somewhere.
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Tuesday, September 14th, 2021 AT 7:51 AM

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