4 wheel disc conversion Bleeding problems - Chevelle Tech
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post #1 of 12 (permalink) Old May 2nd, 13, 11:00 AM Thread Starter
Adam
 
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4 wheel disc conversion Bleeding problems

Hi everyone, first post. Read through a lot of information on the site, but didn't quite get a good sense of how to trouble shoot my issue. I converted a 70 Chevelle to 4 wheel disc power brakes from Right Stuff, but can't get the rear brakes to bleed. Orignally the car had 4 wheel power drums. I've gone through the pump the brakes method, gravity bleeding overnight, and bought a Mity Vac to try and pull some fluid through. The Mity Vac had the best luck, but still didn't pull much fluid through, maybe an ounce or two.

I went ahead and went around all 4 last night with the Mity Vac and did get fluid to pull through the fronts (lots of air still), but I'm stumped on the rears. I cracked the rear line coming from the proportioning valve last night for an hour or so, and didn't see anything drip out. Do, I have a bad Master Cylinder, small holes in my fittings (did use unions to tie new lines from the proportioning valve into the original hard lines) incorrect rod, or some other problem?

Site is great, let me know if you need any other information.

Thanks,
Adam
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post #2 of 12 (permalink) Old May 2nd, 13, 11:48 AM
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Re: 4 wheel disc conversion Bleeding problems

You didn't let the master empty out at any time, right? Sometimes you get so into it you forget to recheck the master to make sure its still full of fluid. You would have to reprime the master than.

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post #3 of 12 (permalink) Old May 2nd, 13, 12:16 PM
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Re: 4 wheel disc conversion Bleeding problems

Are these the rear calipers with the lever in the casting to actuate the parking brake? If so they can be difficult to bleed especially if the bleeder is not at the highest point of the chamber when installed.

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post #4 of 12 (permalink) Old May 2nd, 13, 12:58 PM Thread Starter
Adam
 
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Re: 4 wheel disc conversion Bleeding problems

Thanks for the replies.

Hi-po SS 454 - No, I didn't ever get much through the rear when bleeding, the fluid level in the back chamber of the MC hardly dropped at all. I did bench bleed it prior to instalation, and the front chamber did lose fluid when I was working my way around. So, I assumed that the problem was post the MC, but that rear chamber hasn't flown hardly any fluid through.

Philip - Yes, they do have the integrated parking brake assembly. I pulled the pins and rocked the calipers back to get the bleeder parallel with the floor hoping to get them high enough. I cracked the lines on the calipers during the gravvity bleed, and didn't get any fluid through there either.

I'm thinking my problem may be the Master. I've heard that shiming may help, but I'm surprised I haven't gotten anything to the rear.
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post #5 of 12 (permalink) Old May 2nd, 13, 10:27 PM
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Re: 4 wheel disc conversion Bleeding problems

When I had that style on my car it was very difficult to get them bled initially. Tried everything, out of desperation the bleeders were left open and after a few days fluid started to drip out. After that they bled normally...a few months later one started leaking at the parking brake shaft seal. It may have been sucking air around that seal when trying to bleed, never did figure out why they would not bleed properly.

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post #6 of 12 (permalink) Old May 3rd, 13, 6:16 AM
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Re: 4 wheel disc conversion Bleeding problems

Are you using the stock prop valve or the one that came with your disc set up?

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post #7 of 12 (permalink) Old May 3rd, 13, 10:31 AM Thread Starter
Adam
 
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Re: 4 wheel disc conversion Bleeding problems

Thanks for the replies guys. I'm using the new Proportioning valve that came with the kit and eliminated the old distribution block.

To update, I ended up pulling the rear line between the MC and Prop valve, bleeding there then bleeding after the prop vavle, then at the junction between my hard line and flex line at the rear wheel, before finnally bleeding at the rear caliper. Each section had progressively more air, but I was able to get some fluid through the rear caliper.

It's slow going even with the Mity Vac. I'm going to try and bleed them agian this evening, and run through the cycle a time or two. I'm hoping the air clears out, but I'm getting the feeling that I also may be introducing air somewhere in the system that I haven't spotted yet.
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post #8 of 12 (permalink) Old May 3rd, 13, 10:50 AM
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Re: 4 wheel disc conversion Bleeding problems

I had this when I installed the Z28 rear discs on the 65. The Mitey Mite had trouble pulling the fluid thru the adjustable prop valve. I had to resort to the tried and true method - "Honey can you come pump the pedal for me" and that worked - it just needed front to rear pedal pressure to push fluid thru the Prop valve instead of pulling with a low vacuum. FWIW, Ed

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post #9 of 12 (permalink) Old May 3rd, 13, 10:55 PM
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Re: 4 wheel disc conversion Bleeding problems

Quote:
Originally Posted by OLDED View Post
I had this when I installed the Z28 rear discs on the 65. The Mitey Mite had trouble pulling the fluid thru the adjustable prop valve. I had to resort to the tried and true method - "Honey can you come pump the pedal for me" and that worked - it just needed front to rear pedal pressure to push fluid thru the Prop valve instead of pulling with a low vacuum. FWIW, Ed
Same here. The Might Vac got a little fluid back there, but to finish it off, had to do the old pumping method. Worked fine then. Bo
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post #10 of 12 (permalink) Old May 3rd, 13, 11:02 PM
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Re: 4 wheel disc conversion Bleeding problems

Same here, with someone pumping we were able to get the rears to bleed correctly.

It was also noted in the instructions and important to loosen the caliper and tilt it so that the bleeder valve and caliper is tilted back on the rotor. This puts the bleeder valve at the highest point and allows the air to escape and fluid to flow, as also mentioned above. It is a little tricky to do the first time.

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post #11 of 12 (permalink) Old May 4th, 13, 8:52 AM
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Re: 4 wheel disc conversion Bleeding problems

Quote:
Originally Posted by fleming23 View Post
Same here, with someone pumping we were able to get the rears to bleed correctly.

It was also noted in the instructions and important to loosen the caliper and tilt it so that the bleeder valve and caliper is tilted back on the rotor. This puts the bleeder valve at the highest point and allows the air to escape and fluid to flow, as also mentioned above. It is a little tricky to do the first time.
and to add-----the parking brake must be adjusted on each caliper before bleeding

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post #12 of 12 (permalink) Old May 4th, 13, 9:13 AM Thread Starter
Adam
 
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Re: 4 wheel disc conversion Bleeding problems

Thanks everyone. Went back to the pumping method last night and got them to bleed out the air! Did notice a bit of a rotor rub at the left rear last night on the test drive, so I'm going to adjust the parking brake a bit and then bleed once more using the pump method. Thanks for all the help - Adam
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