I have tried to search for this, but I would rather have an open discussion here from experienced forum members.

I've been having some serious brake issues on my 69. Of course, at one time they were great, and then started to develop the usual symptoms of C3 brakes. So far, I have relpaced all calipers to VBP stainless sleeved as well as new rubber lines at all 4 corners.

While bleeding the brakes, I get a strong stream coming from the bleeders, but of course it is full of air bubbles. I could bleed these things all day long and no matter what, it never improves. I took the car out over the weekend and it was pretty damn dangerous to drive. Pedal was very soft and car did not want to stop. I still have the stock master cylinder and it is a manual brake setup.

-Would my next step be purchasing a NEW (not rebuilt) master cylinder? I know this would not hurt, but will it cure my problems?

-How can I properly flush all that crap fluid out?

-Is there a better, more effective method to bleeding these brakes? Other than the old school pump and turn the screw technique.

-And are there any other methods or tips you can help me achieve adequate braking?

Thank you in advance

/Lee

Pics of the car...because we all like pics.

 

I sometimes take a screwdriver and push back the pistons on each caliper. Sometimes it forces air up through and out the MC. Another trick I learned it to pump the brake slow and not all the way down. If you push it hard with air (let's just say in the rear calipers) the proportioning valve will activate a check ball blocking off the rear brakes and it sometimes sticks in position. you can never get the rear bleed properly then the check ball finally moves and your brakes are even worse!

 

I take it still has the Lip seals? If so rebuild with the orings. I bet you are sucking air in on the lip seal.

 

Good advice. I think I may have been doing this, because sometimes the brakes were feeling worse.

Just to clarify, the calipers are O-rings.

 

try hitting the caliper you are about to bleed a few times with a rubber mallet sometimes it helps to dislodge air bubbles, I also used a clear vinyl (I think) hose pushed tight onto the bleeder with the other end submerged in an old clear plastic soda bottle with a bit of the old fluid in it covering the end of the hose. not anymore but I used to bleed brakes A LOT in the car below, like in the shop before every race (because I rebuilt them after every race) then once at the track (pretty much) after every session or at least once a day, and I was using SRF fluid (about $75 a litre), with pretty much the same setup you have with the exception of the o-rings, the lip seals seal better.

 

Not only should the end of the bleed tubing be submerged in some brake fluid, but that hose should be filled with brake fluid, too. If you do not have a 'negative pressure' created by some height of brake fluid in that drain line, it will not help to pull the trapped air out of the system.

Also, if your braking system was drained of most brake fluid, you need to use the sequence of bleeding the brake components in the following order:

Master cylinder; front left caliper, front right caliper, rear left caliper (inner, then outer bleeder), rear right caliper (inner, then outer bleeder). And, as mentioned above, you need to be sure that the shuttle valve in the proportioning valve block is centered [and not shifted toward one side or the other]; then bleed each component slowly, so that P-valve doesn't get tripped during the bleeding process.

Finally, when you think it is 'good to go', button it up, take it for a nice drive...over some RR tracks, if possible..., then do a final bleed on each caliper to get any dislodged/trapped air out. The GM manual says to use a rubber mallet on each caliper as it is bled (to dislodge that trapped air); but I've found that a bit of driving does that job better than a mallet.

 

These are awesome suggestions...thank you and please keep them coming.

 

Hi,
You can waste your time screwing around with bleeding your brakes the traditional way. Or you can purchase the Motive Brake Bleeder and be done in one hour tops. I've bled brakes in a ton of cars and when I became a C3 owner I never thought twice about it until I had to bleed the brakes. It beat me up pretty bad. Finally I caved and bought the Motive and my brakes are great first time every time. Just make sure the master cylinder is bled correctly before you start or you will just keep pushing air into your system. Also make sure your rotors are within spec for run-out. If the rotors have excessive run out they will cause the pistons in the caliper to cavitate the brake fluid and create air bubbles in the system while driving. Another interesting characteristic of the C3. Fixed calipers.
Good Luck.

 

Good information. Do you know off hand exactly which Motive bleeder you are using? Part number?

I was thinking of investing in one of these, but do not know much about them and think it would be a great tool especially if I can use it on my other vehicles.

 

Here's a link:
http://corvette-parts.zip-corvette.c...ower%20Bleeder

Don't follow the instructions exactly. Do not fill the actual bleeder with brake fluid. It's messy. Just put brake fluid in your MC reservoirs and then clamp the motive MC adapter on top with a couple of large C clamps. Then pump it up and bleed the brakes. You will have to check the MC regularly to make sure you don't run out of fluid.
Good Luck.

 

Thanks

 

Could anyone give me a quick rundown on how to bleed the Master Cylinder?

 

Hi,
It's quicker to do a search on the forum here on that subject. Been posted many times.
Good Luck.

 

ok...thanks

 

Hook up the little hoses, fill the M/C up and push on the end with a screwdriver until there is no more air.
It helps to tilt the M/C up-down and left & right.

Make sure the end where the screwdriver goes in has the same size hole as the one you take off, some have a large hole and some have a small hole.

 

Use about 15 lbs of pressure on the Motive Brake Bleeder and put in two quarts of new clean fluid. You won't use it all but it's cheap.
I start at the rear, left or right, inner, then outter. Go the other side and do the same, inner then outter. Go to the front, left or right. While the calipers are bleeding strike them repeatedly with moderate force using a rubber or leather hammer to dislodge any air bubbles. Let each bleeder run for 30-60 seconds after you see the last bubble and you have clean fluid coming out.

 

Excellent...thank you above. I feel pretty confident now in getting my brakes up to par. Pretty scary going fast and not being able to stop.

 

Thanks Pete for posting up that article....haven't seen you around in a while

 

If you put clean fluid in a Motive Bleeder (or any pressure bleeder) be sure and flush it out with alcohol after you use it. Brake fluid is hydroscopic and will attract moisture. Leaving fluid in a bleeder is a really great way to pump your system full of wet brake fluid.

with brando too. Just use the bleeder as an air pump- way less messy in case the reservoir top leaks (mine did) and no hassle with washing the bleeder out after you're done.

 

Hi Guys,
I just changed my passenger side rear caliper, I have been trying to get some fluid just to come out of the lines & nothing, dribbles. I have replaced the MC about 3 months ago& changed the fluid, Right now I have some wheels that wouldnt turn, feels like the brake is engaged , some that will just spin like nothing . I an thinking that it is the Porportion valve, should I change it? Is there a test?

Thanks Mark