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Topic: Brake bleeding question

in Forum: C3 Handling Components


Brake bleeding question

Posted: 6/10/13 1:02pm Message 1 of 10
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Germansville, PA - USA
Joined: 1/28/2010
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Vette(s): 1974 Coupe 358ci 4 speed Black w/Medium Saddle interior w/79 custom leather seats. . 1999 C5 Convertible, 6 speed, Atomic orange, Oak interior.
Everybody says to bleed from the farthest away from the master cylinder and work up to the closest. Why does my GM Service Manual say just the opposite? Confused


   

DanT

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Re: Brake bleeding question

Posted: 6/10/13 2:10pm Message 2 of 10
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Long Valley, NJ - USA
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Vette(s): 1972 454 Coupe, 4 speed, Targa Blue with blue interior, luggage rack 2019 Grand Sport Coupe, M7, Ceramic Matrix Gray with gray interior
Glad you asked, I also wanted to know - and does one have to bleed from all three bleeders on the calipers or since they are connected internally is bleeding via just one ok?


Mario

Re: Brake bleeding question

Posted: 6/10/13 2:26pm Message 3 of 10
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Vette(s): 1974 Coupe 358ci 4 speed Black w/Medium Saddle interior w/79 custom leather seats. . 1999 C5 Convertible, 6 speed, Atomic orange, Oak interior.
persico said: Glad you asked, I also wanted to know - and does one have to bleed from all three bleeders on the calipers or since they are connected internally is bleeding via just one ok?

My 74 only has 1 bleeder on the front calipers and 2 in the rear...you have to bleed all of them in a certain sequence.




   

DanT

Re: Brake bleeding question

Posted: 6/11/13 5:11am Message 4 of 10
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Cramerton, NC - USA
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I am certainly not any kind of expert but over the years have read a number of articles written by "experts" and some list it one way, others the opposite. In reality, I don't know that it makes any difference whether you start in the front or back, the fluid has to get from the master to the calipers either way. Dr. Adams may have the answer.


Re: Brake bleeding question

Posted: 6/11/13 10:09am Message 5 of 10
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Duncanville, TX - USA
Joined: 11/8/2003
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas
May not have answers, but I have ideas....Tongue
The recommendation to bleed the closest first is to get air out of the short lines first. This is assuming the entire system is dry. Since the master cylinder has two separate chambers, air in one side shouldn't effect the other side, so it really doesn't matter which end gets it first. The most common method is to do the rears first, unless the entire system is dry. IN that case, doing the fronts first keeps you from over-extending the pistons in the master, and possibly tearing a seal. This is also why I always recommend NOT pushing the brake pedal all the way to the floor when manual bleeding.


You have to bleed BOTH sides of the rear calipers due to the internal passages in them. Some rear calipers have 4 threaded holes for the bleeders, so they will fit on either side of the car, so you may see a caliper with 2-3 or 4 bleeders. Never bother with the bleeder on the lower end of them....it's useless. Bleed the outside bleeder first, then the inner one, on the rears.
The front calipers are not the same....you bleed them from the single bleeder.

With a pressure bleeder, it don't matter which end you do first, either. Every manufacturer has their own way of doing things. In the end, it's whatever works best for you.
Thass my story, and I'm stickin wid it....Wink



Joel Adams
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Re: Brake bleeding question

Posted: 6/11/13 10:46am Message 6 of 10
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Germansville, PA - USA
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Vette(s): 1974 Coupe 358ci 4 speed Black w/Medium Saddle interior w/79 custom leather seats. . 1999 C5 Convertible, 6 speed, Atomic orange, Oak interior.
In my case Joel, I had both rear calipers off to replace trailing arms, and replaced the rubber brake line at both sides while I was at it. Painted calipers while they were off. Pulled front calipers to paint also. I also replaced the master cylinder at that time too due a small leak from the rear of MC. Reinstalled everything and then went to gravity bleed. Got fluid out of the front calipers, but can't get any from rears. I was told that since everything was apart I didn't have to bench bleed master. Some bad advice maybe?


   

DanT

Re: Brake bleeding question

Posted: 6/11/13 7:35pm Message 7 of 10
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Duncanville, TX - USA
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New, or rebuilt MC has to be "bench" bled. I say "has to be", but...if you have a LOT of patience(and brake fluid), you could spend a few days trying to get the air out without a bench bleed.
In your case, I would suggest starting by bleeding the master cyl until there is no air in it, then go to the rear, and start bleeding the calipers. GRavity bleeding works for some, but I've never personally had any luck doing them like that. Then again, I have a pressure bleeder, so that's what I use.


Joel Adams
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Re: Brake bleeding question

Posted: 6/11/13 8:10pm Message 8 of 10
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Vancouver, WA - USA
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Vette(s): 1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.
I think you would want to bench bleed the master in that case.  I use the gravity bleed method as well, but I also could not get the rears to start on their own.  I ended up using my vacuum bleeder on the rears to get them flowing.  I thought they were good enough after that, but I still had a soft pedal.  THEN, I re-bled all four corners with gravity bleed and had a hard pedal.  I let each bleeder drip for about 10 minutes and I concur that the order doesn't really seem to matter, except maybe for inner vs. outer on the rears.  (although my Haynes manual has that order opposite of Dr. Adams, but that manual has led me astray a few times so I'm not sure I'd go with that over Joel)



 

1976 Silver/Firethorn.  L48, 4spd.  Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.

Re: Brake bleeding question

Posted: 6/12/13 7:01am Message 9 of 10
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Germansville, PA - USA
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Vette(s): 1974 Coupe 358ci 4 speed Black w/Medium Saddle interior w/79 custom leather seats. . 1999 C5 Convertible, 6 speed, Atomic orange, Oak interior.
Well I very carefully bled the MC with it on the car since it was full of fluid already, plenty of air in it. After bleeding it I still could not get fluid from rears with the gravity method. When my wife came home from work I tried the good old fashioned method of using her foot and the pump up and hold while I opened bleed screws and what do you know, got fluid out of rears, along with plenty of air. Bled all calipers last night and will give it a try today to see how the pedal is.


   

DanT

Re: Brake bleeding question

Posted: 6/13/13 5:08pm Message 10 of 10
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Gordonvillle, TX - USA
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Just did my 68. Didn't bench bleed, didn't think I needed to.
 Oh Well, took the MC off again after spending a lot of time trying to get the air out. Bench bleed, then reinstalled and went for the left rear outer first then inside, then right rear outer then inside, then bled the front right and finished with the front left. Made it real easy after bench bleeding. Also a good ideal to have a helper this gravity feed and jar bleeding just does not work for me. 




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