94 SC bleeding brakes, - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 12-04-2007, 09:59 PM   #1
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Default 94 SC bleeding brakes,

hi there ive just change over my master cylinder to a new one and also grabed new flex lines and new calipers,i bleed the master properly following the instructions,then i gravity bleeded the entire system which was long over due,then starting at the right rear , i tried to the final bleed but i could not get a steady stream of fluid out after 40 min???any suggestions?? this is my first time bleeding a 92 and up bonny??im out of ideas
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Old 12-04-2007, 10:10 PM   #2
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Granted, I use a pressure bleeder at the shop which does a great job pushing the air out. But, sometimes it takes awhile to get all the air out by pumping the pedal, especially after all the parts you put on. Try pumping the pedal and cracking the lines at the master and to make sure you have good pressure there. You can also try clamping the front hoses to direct the flow to the rear to get that bleed first.
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Old 12-04-2007, 11:14 PM   #3
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Just to review the procedure, here is how I do them (lifted from an earlier post):

OK, The idea is to remove any air bubbles in the brake lines from the master cylinder to each wheel cylinder (rear wheels) or caliper (front wheels).

These directions presume you have a good master cylinder or a new one that has been bench-bled.

You will probably need to remove the rear wheels to gain access to the wheel cylinder bleeders. You may be able to get at the front bleeders on the calipers by turning the wheels all the way left or right. I find bleeding is a lot easier with all the road wheels removed and the car up on stands. Never get under a car supported only by a jack!

Start by filling the master cylinder reservoir and replacing the cap. Don't let brake fluid be exposed to the air - it will absorb moisture from the atmosphere which can cause troubles in the brake lines. What you want is to have a helper pump the pedal a couple of times (press down - release; press down - release) then press down and hold. While he is maintaining pressure on the pedal, you open the bleeder valve on the wheel cylinder or caliper and relieve the pressure by releasing fluid from the bleeder valve. The brake pedal will suddenly go down, at first nearly all the way to the floor. The helper must not allow the pedal to come up while the bleeder valve is open or air will be sucked in through the bleeder valve. At the wheel, when the fluid flow stops, close the bleeder screw and instruct your helper to release the pedal, then "pump and hold" again. After a few times, depending on how much air is in the lines and where the air is located, you will notice as you open the bleeder valve, that the fluid flow is interrupted by escaping air. It kind of makes a "spitting" sound. That is good - that'* the air you are trying to remove. Keep repeating the procedure until the stream of fluid is solid - no air - and clean in appearance.

While you are bleeding each wheel, after about five or six squirts, check the level of fluid in the master cylinder reservoir. If you let the reservoir go empty, you will introduce air into the lines and you will have to bleed the master cylinder and all the brakes again.

I like to place a box wrench on the bleeder screw nut in a position that allows me to both open and close the valve (hopefully) without repositioning the wrench. I then attach a length of flexible vinyl tubing (maybe 3/16" inside diameter) that fits tightly over the end of the nipple on the end of the bleeder. I run the hose into a plastic pan to catch the fluid that comes out. Be careful, brake fluid removes paint. Also, don't use more than a couple of foot-pounds of torque to close these little bleeder screws - they are not solid and they can break off very easily.

There are a couple of inexpensive one-man methods. You can use a vacuum pump to suck out the air from each line, but the problem with that is that you have to open the bleeder screw to open the line and when you do, you usually end up sucking some air through the threads on the bleeder screw making it difficult to know when you have all the air out. An older method is to take the hose described above and put it into a (clean and dry) coke bottle with the end of the hose submerged under a couple of inches of brake fluid. This is not a bad idea, even with a helper, cause if your helper screws up and releases the pedal when the valve is still open, it will suck mostly fluid in from the bottle instead of air. The problem with this method is the same as with the vacuum pump. That is, on the release stroke, if the valve is open, air can be sucked into the system through the threads on the bleeder screw.

Be careful if your bleeder screws are corroded. They will break off in the cylinder or the caliper with surprisingly little force applied, and then you have a real piece of work on your hands. A good plan is to squirt around the bleeder screw (not into it) with a good penetrating oil like power blaster, kroil, or sea foam deep creep (WD-40 is not very good for this). Remove the cap from the screw and give it a couple of taps square on the end of the screw with a small ball-pein hammer, and squirt again to encourage the oil to penetrate the threads. Best if you can let it sit overnight, but give the oil at least 30 minutes to work before you try to open the bleeders.

If your bleeders don't have the little rubber caps on them, make sure the passage is clear to let the fluid out. Sometimes you have to clean them out with a small drill bit.

The traditional method is to start at the wheel farthest from the master cylinder, usually the right rear, and work to the shortest run, i.e., the left front. As you work your way around, the pedal should become firmer and progressively higher from the floor. When you are done, if you have removed all the air, the pedal should be firm, there should be no "sponginess," or softness when depressed.

I would not touch the ABS system other than to very carefully clean, remove, and plug the top end of the hose that runs down to the ABS pump reservoir when you change out the master cylinder. It is very important that you do not introduce any dirt into any part of your brake system.


Here is what the FSM says:

According to the factory service manual for the '92 Bonneville with ABS, the bleeding procedure is pretty much as above EXCEPT they instruct that before you start to bleed the brakes, you deplete the vacuum in the booster by applying the brakes a few times with the engine off. (This is the power brake booster vacuum can behind the master cylinder, NOT the ABS pump.) They also instruct that the helper press slowly down on the pedal and hold only once for each time the bleeder valve is opened. Then the pedal is released and you wait 15 seconds before pressing down only once again. This is done with the ignition and engine off.
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Old 12-05-2007, 06:21 PM   #4
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thanks for the detailed procedure , i have been following every detail carefully,but i still have no pedal at all,i started at the rr ,when i open up the bleeder , it only drips with no pressure there at all, even still after an hour on the rr ,there is no difference, just continual dripping,im ready to pull the rest of my hair out!!
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Old 12-05-2007, 08:25 PM   #5
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Quote:
Originally Posted by Brad_94
thanks for the detailed procedure , i have been following every detail carefully,but i still have no pedal at all,i started at the rr ,when i open up the bleeder , it only drips with no pressure there at all, even still after an hour on the rr ,there is no difference, just continual dripping,im ready to pull the rest of my hair out!!
It seems like the master cylinder may not be bled. If it were pumping fluid properly, and you were not losing fluid somewhere else, the only place for it to go would be out the only opening in the system, i.e., the rr bleeder screw. Are you sure the rest of the system is tight?

The only other explanation I can think of off hand would be if there is a restriction in the line to the rr that prevents a normal flow of fluid from the MC to the rr bleeder.

Try another bleeder screw, like the lr. If you get good flow there, look for a restriction in the rr line. If not, re-bleed the MC.
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Old 12-05-2007, 08:33 PM   #6
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Try bleeding the fronts first just to get alot of air out. You don't have to do a great job cause you'll be doing them again when you go back and do them in the right order.

If you get the same problem on the front then you probably have a bad rebuild on the MC.
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Old 12-05-2007, 09:45 PM   #7
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right on thanks for the ideas,would the bitterly cold out door temps not help either?
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Old 12-06-2007, 01:48 AM   #8
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Quote:
Originally Posted by Brad_94
right on thanks for the ideas,would the bitterly cold out door temps not help either?
Besides making you terribly uncomfortable, shouldn't make any difference. Unless... you somehow have moisture in that rr line or in the MC somewhere that has frozen to create the restriction we were theorizing about earlier.
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Old 12-06-2007, 11:02 PM   #9
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You are pushing the brake pedal with the bleeder open, then closing the bleeder before releasing the brake pedal arn't you? OR you do have a tube from the open bleeder to a container partially full of brake fluid so that no air is being sucked back up the line?


A no brainer for someone who has done this before, but it could be news to someone who hasn't bled brakes before.
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Old 12-13-2007, 12:08 PM   #10
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hi there ,i still have no luck,i have bleed the mc three times,i have bleed each line,many of times???but i still have no pedal and no pressure ,i wondering if it is the booster or air in the abs controller ????
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