No brake pedal pressure

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GARRICK.CLARK
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No brake pedal pressure

Post by GARRICK.CLARK » Mon May 07, 2018 10:54 am

Hi guys.
I fitted rear discs on my 67 bug, bled the system, fronts and rears and have no pedal at all. The fluid does come out of the nipples, Cant see it being trapped air. Any Ideas on this.
P.S. It was ok before swapping the rear brakes over to disc.

Ol'fogasaurus
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Re: No brake pedal pressure

Post by Ol'fogasaurus » Mon May 07, 2018 1:32 pm

Make sure that the MC is the properly sized for your new brake setup.

Are you sure that there is not any air trapped in the line. While bleeding the brakes if you get too low on fluid in the MC & res you can re-introduce air into the lines. That could give you fluid in the discs but a soft spot somewhere in the lines. Sometimes a controlled "gravity bleed" can work either for you or against you.

Try re-bleeding starting with the wheel farthest away from the MC and work to the closest one as not doing that can cause problems.

Re-check all the joints to make sure that there is no air getting in even if they are not leaking. I had this problem so when I took the lines apart when replacing the turning brake cylinder I used the same fittings but they seated better this time and the problem was solved.

Check/replace the soft lines as as they age they can swell reducing the inside diameter or even close off completely. I am not a big fan of braded SS lines as the SS strands can age harden with all the flexing and the strands can break leaving to injury to fingers or damage to the line itself. During WWII they were used on some airplanes and the mechanics started to use them on the hot rods but at lengths where they started to fail. Looks cool but not what they were designed for.

Lee

GARRICK.CLARK
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Re: No brake pedal pressure

Post by GARRICK.CLARK » Mon May 07, 2018 2:51 pm

Hi Lee, I did started the bleed process from the furthest caliper. When I did the pumping of the pedal to bleed the brakes there didn't seam to be any pressure at the M.C. the pedal just goes down and up like its not attached to a M.C . fluid does exit from the nipples.

Ol'fogasaurus
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Re: No brake pedal pressure

Post by Ol'fogasaurus » Mon May 07, 2018 6:24 pm

Got pictures? Assuming everything else is OK then I would have the MC itself checked. Here is something that might give you some help: https://www.jbugs.com/category/vw-dual- ... aster.html Notice the dual chamber discussion.

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Jadewombat
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Re: No brake pedal pressure

Post by Jadewombat » Mon May 07, 2018 8:07 pm

Try the two-person method of bleeding, even race teams do this. Fill up the reservoir and a small bottle with brake fluid, have one person starting out at the right rear wheel, one person in the drivers' seat. String up a clear bleeder line off the valve so the line is elevated above the valve so nothing but fluid could be sucked back in. Pump the pedal a few times and HOLD medium pedal pressure on the last pump, have the person at the wheel crack the bleeder valve and don't let the pedal go all the way to the floor. Repeat a few times then go to the next wheel. Now, very important, after you've done all four wheels check how stiff the pedal is and do all four again one more quick time--I've found there is sometimes air still in there that gets pushed from one side to the other through the 'T'. The whole process takes about 20 min. Finish and go drink a cool one.

Never had any luck with those pumps or one-way bleeder valves or bench bleeding or whatever.

Ol'fogasaurus
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Re: No brake pedal pressure

Post by Ol'fogasaurus » Mon May 07, 2018 9:14 pm

That is the way I was taught JW but the 4 wheel disc brakes conversion, from what I understand, does need the dual chamber MC especially as a safety device and front to rear balance. That is why I gave the URL. The bigger MC is also covered the too. Again, unless the soft lines have been replaced recently that I would consider as a safety thing also.

Lee

Ol'fogasaurus
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Re: No brake pedal pressure

Post by Ol'fogasaurus » Tue May 08, 2018 4:41 pm

Garrick, remember you are not dealing with 4 wheel drum brakes now but discs at all four corners. The rules have no changed so the MC has to be changed to balance out the system. Also, "Gramma"/stock usage vs. harder usage can change the balance requirements also.

Also, when you open up a brake line you allow are reducing the line pressure and allowing air into the system even though it may not look like it. If they are open for more than a few minutes the air in the line problem can get worse as drainage from each side of the join can happen.

Lanner
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Re: No brake pedal pressure

Post by Lanner » Wed May 09, 2018 4:34 am

Are the rear calipers with built in ebrake? If so you have to actuate the ebrake mechanism to get the air out of it. So with a two person bleed, do the usuall pump-pump on the pedal, then work the ebrake a couple times and release, then hold the pedal down while you helper bleeds the nipple. This gets all the air out. Good luck.

GARRICK.CLARK
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Re: No brake pedal pressure

Post by GARRICK.CLARK » Tue Jun 05, 2018 2:35 pm

Hi Guys. It turned out the new CSP Master cylinder was faulty. Got a replacement and now have a pedal. Albeit a low one. I've found out that I needs a 2 lb pressure valve fitted to the brake pipe that feeds the rear calipers. Thanks FJCAMPER. That's on its way to me in the post . So hopefully soon I'll get a higher pedal soon.

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andy198712
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Re: No brake pedal pressure

Post by andy198712 » Thu Jun 07, 2018 10:27 am

ouch, given the cost of them you'd hope for better quality

GARRICK.CLARK
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Re: No brake pedal pressure

Post by GARRICK.CLARK » Sat Jun 09, 2018 12:10 pm

Fitted the valve ,right on the outlet on the master cylinder that feeds the rear brakes. Gotta bleed it Yet but I think its still gunna be rubbish.
I'll let ya no if its worth buying or not. I'm probably gunna say NOT.

Ol'fogasaurus
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Re: No brake pedal pressure

Post by Ol'fogasaurus » Sat Jun 09, 2018 12:46 pm


GARRICK.CLARK
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Re: No brake pedal pressure

Post by GARRICK.CLARK » Sun Jun 10, 2018 3:16 pm

Hey Thanks ol'fogasaurus Good read, I bled the brakes today and had no pedal again. So by now I'm a very pxxxed off with it. So I bled it again. This time I jacked front end up high. Removed the proportional valve, Removed the front pads to check the thickness of the pads and pushed the pistons all the way back. The front pads are a bit low and could do to be thicker, so I refit the pads , blead the front brakes and hey presto I have a good high pedal and don't no how I achieved it. I think it was pushing the pistons on the front all the way back which pushed fluid back into the reservoir and possibly pushing air out the reservoir cap hole. I'll fit new thicker pads and be done with it.

Ol'fogasaurus
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Re: No brake pedal pressure

Post by Ol'fogasaurus » Sun Jun 10, 2018 5:11 pm

How are the pistons mounted? Vertical or horizontal. That alone could make a difference but so could the pistons if they were stuck in an applied position (IOW, the front brakes had been on and that is what wore the pads thin. A guess only!)

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