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Hello everybody.
I just imported a '76 coupe into south-eastern France where I live, (I'm Canadian), and am getting it ready for the government safety inspection so I can get a French ownership. There was way too much brake pedal travel, (half way to the floor), so I decided to try the easiest thing first and bleed the brakes. The right rear calliper, inside half, had enough air in it to make me wonder. I've bled a lot of brakes in my time, but I've never seen anything like it, it just kept coming out, taking about 25 pedal strokes to finally, I hope, finish up. All the other callipers were normal, a bubble here or there, and some with none at all. Has anybody run into this much air? Is it normal?
Thanks for any help or opinions.
My left front caliper was that way... no matter how much I tried, it appeared to still have air present.
Now, I'm in the process of bleeding mine after installing new flex lines and a master cylinder... still have a spongy
pedal at this point.
I'm gonna' try the reverse bleed procedure where you basically inject fluid through the open bleed port
on the calipers and let the air bubble out into the master cylinder reservoir.
I'm not sure why, but the conventional bleeding procedure really doesn't work well on C3 cars.... it might
have something to do with the angle of the Master Cylinder and require the car to be raised in the rear to level
the MC enough to get all the air evacuated from the system.
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Hi and welcome!
Pedal travel:
A C3 brake pedal seems to have a lot of travel and takes a little time to get used to.
With only 6 inches of total travel and 2 inches of travel before the brakes engage it may seem like the travel is excessive, but it is not.
Bubbles:
Could it be that the threads on the inside bleeder was letting the air in?
Rotor run-out:
If after driving a number of miles and the brakes get low again then the next step is to make sure that the rotors are turning true and that both sides are parallel.
Here's how to check the run-out:
Did you carefully look at each caliper piston seal for leaking brake fluid?
Even if no leak if the rotor has too much run out the caliper seal will ingest air over time.
Thanks everybody, and especially Peterbuilt for the drawings. I would be trying and trying to get very little pedal travel when there is a fair amount built into the system.
I don't have a reservoir cap adapter for a pressure bleeder, so if the brakes still don't feel good when I get it back off the hoist, (waiting for new tires to be mounted on the rims), I'll try the gravity bleeding idea.
I tried the reverse bleed procedure today.... couldn't get it to work. Just pushed most of the fluid out around the threads on the bleeder fitting
and generally made a mess on my clean floor. Gave up after about one minute of that bs... although it might work if the threads were better sealed
into the caliper with teflon tape or similar.
Went back to the old standard method (with help from the wife pushing the pedal) and got most of the air out of the system. Pedal feels
much better than before... but I'm still gonna jack up the back of the car (to level the master cylinder) and do a quick check for any bubbles
that may be trapped in there due to the mounting angle.
hdeyong
Do you have a pressure bleeder? If not, then I recommend you get one, or make one. It's easy to make one if you can't find one. Ask if you need pointers and/or references.
I made my own pressure bleeder since I didn't want to wait for shipping..... worked so well that I've never replaced it.
I can't figure out the reverse bleeding idea. Wouldn't you be trying to push the air bubbles down, and then back through the whole system?
I agree on the pressure bleeder. Me and a buddy of mine rally two of his cars, a '69 MGC and a '67 Mini Cooper S, and we pressure bled the brakes on both of those. Worked perfectly. I'm driving the car tomorrow, and if the brakes aren't really good, I'll order a replacement MC cap and make it into a part for the pressure bleeder.
I tried the gravity bleeding and very few, small bubbles came out. It did fill the tube with fluid up to the height of the MC, so maybe I did actually get all the air out.
My car has a level MC, so at least I don't have to work around that.
The air wants to (rise) go up towards the master cylinder.... regular or pressure style bleeding forces it down through the system and out the bleeder fittings.
The theory works better than the actual application...in my case anyway. I was using a cobbled together tool, basically a large syringe and vinyl tubing but it was too messy for my clean floor.
There are some commercially available reverse bleed kits available with videos on Youtube if you want more info.
The air wants to (rise) go up towards the master cylinder.... regular or pressure style bleeding forces it down through the system and out the bleeder fittings.
The theory works better than the actual application...in my case anyway. I was using a cobbled together tool, basically a large syringe and vinyl tubing but it was too messy for my clean floor.
There are some commercially available reverse bleed kits available with videos on Youtube if you want more info.
mardyn
Right, but the feed line usually goes in near the bottom of a calliper or wheel cylinder, and the bleeder is at the top. I'd think you were trying to force the air bubbles to go down to get out of the calliper and into the lines back to the MC. It just doesn't seem like a very good idea to me. I suppose it must work. but it seems to go against logic somehow, trying to force air downwards.
The air wants to (rise) go up towards the master cylinder.... regular or pressure style bleeding forces it down through the system and out the bleeder fittings.
The theory works better than the actual application...in my case anyway. I was using a cobbled together tool, basically a large syringe and vinyl tubing but it was too messy for my clean floor.
There are some commercially available reverse bleed kits available with videos on Youtube if you want more info.
mardyn
Ok. Just watched the reverse bleed kit video.
First, Stacey David gets paid big bucks to endorse anything, regardless if it works or not. I would have loved to seen the outtakes when brakefluid sprayed everywhere.
Second, he does the left front caliper. Its the easiest to watch the MC by yourself. It would take two people to run this operation trying not to make a mess.
Third, the tool itself looks like it was made by Mattel Toys. Way to much cheap plastic for my liking.
Fourth. I would question the theory a bubble at the passenger rear would find its way to the MC on a complicated system like the C3. To many dips, turns, distribution block, then Proportioning Valve and past the MC piston seals.
I know what you are getting at, air bubble wants to rise to the MC. But brakefluid likes to sink. That's why the "gravity bleed system" works so well.
But to each their own.
Last edited by HeadsU.P.; Nov 16, 2019 at 10:02 AM.
hdeyong - If you are going to bleed your brakes the best product is the MOTIVE Power Bleeder. The fastest and by far the best was to bleed your brake system. You will need to order the appropriate adapter for your GM master cylinder. In addition two 6in C clamps. This bleeder is truly amazing.
Just a note: The proportioning vale could also cause an issue.
hdeyong - If you are going to bleed your brakes the best product is the MOTIVE Power Bleeder. The fastest and by far the best was to bleed your brake system. You will need to order the appropriate adapter for your GM master cylinder. In addition two 6in C clamps. This bleeder is truly amazing.
Just a note: The proportioning vale could also cause an issue.
Good luck
Thanks for the tip on the proportioning valve. I have a bleeder that works off of a tire with 10-15 PSI in it. My buddy and I have used it twice on his cars, (British), and it seemed to work really well. I'm ordering a MC cap so I can make it work on the Vette. I think, as you say, it should do the job.
hdeyong - If you are going to bleed your brakes the best product is the MOTIVE Power Bleeder. The fastest and by far the best was to bleed your brake system. You will need to order the appropriate adapter for your GM master cylinder. In addition two 6in C clamps. This bleeder is truly amazing.
Just a note: The proportioning vale could also cause an issue.
Good luck
I second this. Somewhere on the forum I have a write up. Definitely make sure you get (2) 6" C clamps. Put a small piece of wood on the top and bottom of the master cylinder between the C clamps so you don't put markings in the top plate of the motive power bleeder or scrape the paint from the bottom of the master causing rust to form over time.
I second this. Somewhere on the forum I have a write up. Definitely make sure you get (2) 6" C clamps. Put a small piece of wood on the top and bottom of the master cylinder between the C clamps so you don't put markings in the top plate of the motive power bleeder or scrape the paint from the bottom of the master causing rust to form over time.
Be mindful of the proportioning valve.
I also used this type of bleeder. It's called "SpeediBleed". I think I paid 120 or so for it. It's a company in Canada. I stuggled like most. After using the speedi bleed I have a great pedal.
Bleeding brakes
