Spongy brake pedal - Team Camaro Tech
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post #1 of 17 (permalink) Old Apr 28th, 17, 05:37 PM Thread Starter
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Spongy brake pedal

Alright first​ post here I have a 69 Camaro I'm have issues with a very bad brake pedal feel i can push pedal to the floor and the car and can't hardly feel them grabbing. I have LS1 front brakes on my car and just installed an inline tube rear disc conversion I have a 7/8 wilwood master cylinder and proportioing valve. I've bleed the master multiple times along with bleeding the brake multiple times I'm stumped thanks
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post #2 of 17 (permalink) Old Apr 28th, 17, 09:03 PM
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Re: Spongy brake pedal

Sounds like air in the system.

Make sure that you have the front calipers installed with the bleeders at the TOP.

I looked at inline tube's website and couldn't find a rear disc conversion. I'm just guessing that this is the type of rear discs you have, fairly common - if not disregard.



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post #3 of 17 (permalink) Old Apr 28th, 17, 09:12 PM
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Re: Spongy brake pedal

If you have a power booster, you need to bench bleed the master cyl before installing it. The angle of the Master cyl on the booster will trap air and you can't bleed it out. Another quick thing that sometimes helps is to bleed the Master cyl by cracking open the lines at the Master like a bleeder.

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post #4 of 17 (permalink) Old Apr 29th, 17, 03:25 AM Thread Starter
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I'm going to pull master cylinder again to try and bench bleed it again
Yes the rear cailpers and pretty common ones I believe and no brake booster manual brakes
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post #5 of 17 (permalink) Old Apr 29th, 17, 03:38 AM
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Re: Spongy brake pedal

All bleeders facing up ?

7/8" MC for 4 wheel disc ? I'm not sure that is correct or not....double check with your supplier.

Also, in a quick search I found this....

Master Cylinder Bore Size Affects Pedal Travel Distance and Effort | Master Power Brakes
Quote:
A little general advice about selecting bore size in your master cylinder may be helpful. Decreasing MC bore size will decrease your pedal effort and increase your pedal travel. Conversely, a larger bore in your car’s master cylinder will, all other components being consistent, increase your pedal effort and decrease your pedal travel. As with some other brake parts purchases, this comes down to your preference for how the brakes “feel” under foot when you are driving.

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post #6 of 17 (permalink) Old Apr 29th, 17, 06:15 AM
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Check your pedal ratio. When i switched from drums to wilwood disc set up my pedal had to be adjusted quite a bit.
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post #7 of 17 (permalink) Old Apr 29th, 17, 06:25 AM
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Re: Spongy brake pedal

Quote:
Originally Posted by DOUG G View Post
All bleeders facing up ?

7/8" MC for 4 wheel disc ? I'm not sure that is correct or not....double check with your supplier.

Also, in a quick search I found this....

Master Cylinder Bore Size Affects Pedal Travel Distance and Effort | Master Power Brakes
7/8 is widely used for manual disc setups. I used one with C5 front and LS1 rear. Pedal was not spongy at all. Quite firm. Pedal effort was a little high but they were manual brakes after all.

Spongy to me indicates air in the system.

I used a low cost rear disc setup once and the bleeder was not at the top when installed. Instructions stated you had to unbolt the caliper and rotate it to bleed them. Very Mickey Mouse.....

Is the prop valve turned the correct direction for max rear brake? It is a little counter intuitive which direction to turn it.

I have had good results using a Phoenix reverse bleeder that I picked up on eBay.

Don

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post #8 of 17 (permalink) Old Apr 29th, 17, 07:43 AM
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Re: Spongy brake pedal

I keep seeing this problem with rear disc brakes. They are apparently notoriously hard to bleed. X2 on bench bleeding the master again.
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post #9 of 17 (permalink) Old Apr 29th, 17, 11:36 AM
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Re: Spongy brake pedal

Quote:
Originally Posted by Livewire440 View Post
I'm going to pull master cylinder again to try and bench bleed it again
Yes the rear cailpers and pretty common ones I believe and no brake booster manual brakes
Did you look at the video I posted? Are those the rear brakes you have? If that is what you have, follow the instructions presented. You can bench bleed the MC a hundred times, but unless you properly adjust the parking brake and rotate the caliper to get the bleeder parallel to the ground when bleeding you'll never get a good pedal. Yes, it's Mickey Mouse, but if you do those two things they work. I helped a friend install those on his Chevelle, and that was the answer.
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post #10 of 17 (permalink) Old Apr 29th, 17, 02:14 PM Thread Starter
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Yes my rear disc look very similar to those in the video but I do not have parking brake I bleed master cylinder again it seems that the master has accumulation of air in rear port when trying to bleed like an internal leak ? Did everything again today had some pedal pressure then went away after sitting for a few minutes ?
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post #11 of 17 (permalink) Old Apr 29th, 17, 02:18 PM Thread Starter
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Pedal ratio is 6 to 1. I called wilwood yesterday and they said 7/8 would work but 15/16 would be ideal I'm starting to think master cylinder is bad I will call them Monday morning
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post #12 of 17 (permalink) Old Apr 29th, 17, 03:36 PM
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Re: Spongy brake pedal

If you think it is the master remove the lines and plug the ports. If you get a firm pedal it should be ok. This is an alternate method to bleed a master cylinder.

Don

1969 Camaro LSA 6L90E AME subframe and IRS
1969 Camaro vert LS3 4L65E Ridetech level 2 - sold
1959 El Camino project
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post #13 of 17 (permalink) Old Apr 29th, 17, 07:38 PM Thread Starter
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If I plug the ports on the master cylinder I can not push pedal down
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post #14 of 17 (permalink) Old Apr 29th, 17, 07:40 PM
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Re: Spongy brake pedal

Quote:
Originally Posted by Livewire440 View Post
If I plug the ports on the master cylinder I can not push pedal down
I think that says your master cylinder is ok.

So you have no parking brakes on your car?

Don

1969 Camaro LSA 6L90E AME subframe and IRS
1969 Camaro vert LS3 4L65E Ridetech level 2 - sold
1959 El Camino project
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post #15 of 17 (permalink) Old Apr 29th, 17, 07:48 PM Thread Starter
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Correct no parking brakes. When I bench bleed the master cylinder I could see bubbles in my rear port coming through they would clear up be fine wait 5 min pump it again and have bubbles in the line ?
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