No brakes, no air in lines?????

[davidpa28140]

Hi again guys, after replacing the front control arm bushings I decided to put on new front brake pads . My latest problem is now I have very little to no brakes. I have bled three corners several times (the front passengers side has the bleeder broken off) The pedal goes to the floor each time I have my assistant press it down. I have been pumping the pedal 10 times, then opening up the bleeder , unfortunately there is no more air coming out and I still have no brakes. I have not been losing any brake fluid and I can’t find any leaks, so I’m kind of lost here….
I did notice a small nick in the front drivers side caliper dust seal, but no fluid at all, I’m really not sure if that might be part of my trouble or not.
I replaced both rear wheel cylinders tonight, and ordered a front caliper and master cylinder that will be tomorrows adventure.
What really has me lost here is no fluid loss??? Is this a master cylinder problem, maybe?

Any ideas would be great,
Thanks again, Dave

[82vdub]

Where did the air come from in the first place? Changing brake pads doesn't require the brake system to be opened. Did it show up after you did the rear wheel cylinders? If so, when you did the rears, did you let the master cylinder run out of fluid?

If you let the master cylinder run out of fluid, then you'll have air in the master cylinder. To get rid of it, you need to bench bleed it. I'm not sure if you can get all the air out of a master cylinder when it's on the car. To do a good job at bleeding a master cylinder, it will take you 15 minutes, a vice and a pushrod in the garage. It's a job, but do take that extra 5 minutes to make sure zero air is in the master before saying it's done and install on the car.

Also, it's concievable that the master cylinder is shot, or that the rear brake ajustors aren't adjusted right, making the pedal go to the floor trying to expand the rear shoes. I also find that under most circumstances, undoing the bleeders on the calipers/wheel cylinders and letting gravity work will bleed the air out of most brake lines. I've done this the last couple times I've done brakes with good results.

[davidpa28140]

Thanks vw dub, I didn't let the master cylinder run dry ( I have done that in the past though;( )
Most of the air was in the back after replacing the wheel cylinders. I did get a tiny bit out of the front which I did first.

I had to push the calipers back in order to fit the new pads, but I don't see how that would allow air in there.

Do you think I should start with the master cylinder tomorrow first? My gut feeling is I will be breaking lines when I get to the front caliper, but maybe not......

Thanks again,
Dave

[Op-Ivy]

Sounds like that front one that you can't get at is causing the problem. I would look at trying to replace the bleeder screw.

[davidpa28140]

Just replaced the master cylinder. Still no pressure build up after 100 pumps or so. I am getting no air out of the lines at all...

Thinking maybe gasoline and a match might be next........... still not losing any fluid?!

[davidpa28140]

I think op ivy might be on to something, after exhausting all other avenues I tried using an "easy out" (which for me have never ever been easy) to remove the bleeder from said front caliper. I managed to break it off which I find to be a game stopper. After the brief period of abusing the english language I thought I would try pumping up the brakes again and sticking a board between the pedal and seat in order to hold the pedal. I then went out and opened up the brake line feeding said caliper. After allowing some fluid to run out I closed the line and went back in the cab to pump the brakes up again and they appeared to actually build a little pressure. I ordered a new front caliper which should be here tomorrow, hopefully this will end my saga that began with just replacing front control arm bushings............

[FineFrank]

Take the calipers off and make sure the pads are installed correctly. If they aren't. the pads will probably be bent. I helped a mechanic on an 83 recently with the same problem, and the pads weren't in right. New pads, correctly installed, solved it.
In no way ought you think I'm putting down you mechanical abilities; just trying to help.
One other thing: the master cylinderfront circuit controls one front and one rear wheel, so bleed opposite front and rear wheels, rear first and front next.

[Quantum-man]

Hi again guys, after replacing the front control arm bushings I decided to put on new front brake pads . My latest problem is now I have very little to no brakes. I have bled three corners several times (the front passengers side has the bleeder broken off) The pedal goes to the floor each time I have my assistant press it down. I have been pumping the pedal 10 times, then opening up the bleeder , unfortunately there is no more air coming out and I still have no brakes. I have not been losing any brake fluid and I can’t find any leaks, so I’m kind of lost here….
I did notice a small nick in the front drivers side caliper dust seal, but no fluid at all, I’m really not sure if that might be part of my trouble or not.
I replaced both rear wheel cylinders tonight, and ordered a front caliper and master cylinder that will be tomorrows adventure.
What really has me lost here is no fluid loss??? Is this a master cylinder problem, maybe?

Any ideas would be great,
Thanks again, Dave

So the brakes operate a little bit, but not much. It could be that your bleed off screws are knackered. Do you get fluid out when they are loose, but just not air? If no fluid either, then try loosening the hydraulic pipe nut instead (a little messy I know )
On the Quantum I find very litle air comes out of the front lines because they tend to self bleed as the lines are mostly uphill back to the mastercylinder. Could your front lines be clogged?

[82vdub]

One other thing: the master cylinderfront circuit controls one front and one rear wheel, so bleed opposite front and rear wheels, rear first and front next.

This would mean that there are two main brake lines running under the chassis feeding the rear wheels? I think if you look a little closer, there's only one main line running under the car feeding both rear wheels. This situation isn't so.

I would also tend to think that in a panic stop situation on road surfaces that aren't quite ideal and one master cylinder chamber braking system failed would put the car into a questionable controllable situation, since only one side of the vehicle is doing any braking. It's bad enough on snowy roads when either the front or rear braking system is compromised, but to try to control a car when only one side is braking on slippery roads is allowing the car to try to stop it's forward momentum by exerting a potential twisting motion to the mass it's trying to stop. Not good.

[Quantum-man]

One other thing: the master cylinderfront circuit controls one front and one rear wheel, so bleed opposite front and rear wheels, rear first and front next.

This would mean that there are two main brake lines running under the chassis feeding the rear wheels? I think if you look a little closer, there's only one main line running under the car feeding both rear wheels. This situation isn't so.

I would also tend to think that in a panic stop situation on road surfaces that aren't quite ideal and one master cylinder chamber braking system failed would put the car into a questionable controllable situation, since only one side of the vehicle is doing any braking. It's bad enough on snowy roads when either the front or rear braking system is compromised, but to try to control a car when only one side is braking on slippery roads is allowing the car to try to stop it's forward momentum by exerting a potential twisting motion to the mass it's trying to stop. Not good.

On the Quantum, front right, and rear left go to one chamber, and the remaining to the other. Bleed sequence is RR, LR, RF, LF according to the Bentley

[FineFrank]

This would mean that there are two main brake lines running under the chassis feeding the rear wheels? I think if you look a little closer, there's only one main line running under the car feeding both rear wheels. This situation isn't so.

It's possible that you didn't understand my post, as I omitted much detail for the sake of brevity. But I'll wager that if you look under any 83 caddy or Rabbit, you'll find it just as I've described- each circuit on the master controlling one front and one rear wheel. I was suprised to see it the first time I saw it too.
Maybe that's why some Rabbits (though not mine, thankfully) have a brake pressure regulator that modulates the rear brakes according to the rear axle load.
In any event, sorry to hijack the thread with my long windedness.

[82vdub]

Well, I definately learned something today, for sure! I have never heard of crossing over on the same braking circuit before. In the spring, I will have to look under my Rabbit and double check, but I can only remember one line, but I also don't believe there's an axle position valve under it like there is on my Jetta.

[davidpa28140]

To close the thread here; I put on the new caliper today(the one with the operating bleeder) and after a brief bleeding of air I have brakes! For the benefit (amusement?) of others I will have to admit the inside brake pad was bent…. I’m not sure this was the whole trouble, but I can’t say it wasn’t. What makes me unsure is that the brakes worked somewhat last night after I opened the brake line feeding the caliper so; it’s hard to say… I’ve done stupid before and seeing as this project started out 4 days ago with just building a lower strut support and installing new bushings, I very well could have put the pads in wrong . Jury’s still out… I bleed the brakes in this order RR,LR,FR,FL honestly didn’t notice if there where two lines or one feeding the back.

Some other observations, as I mentioned this started out as just replacing the control arm bushings, while removing the bushings I pulled to hard to get the front one out of it’s perch which in turned pulled the axle shaft out of the outside cv joint, which meant the axle had to be removed/reassembled and installed. Mine has Sirrocco axles under it so this may or may not happen to you. ( they were required when I did the TDI/02A swap)
I know there is a little bit of controversy about the use of never seize and brakes, but I took the liberty of applying a little to the bleeders and lines that did open, as I have found over the years that they notoriously freeze and break.
Thank you all for your insights and ideas,
Dave

[rabbit_man]

Well, I definately learned something today, for sure! I have never heard of crossing over on the same braking circuit before. In the spring, I will have to look under my Rabbit and double check, but I can only remember one line, but I also don't believe there's an axle position valve under it like there is on my Jetta.

All rabbits have crossover lines, early ones have a load sensing valve and later ones have a brake proportion valve.

It's mounted under the brake booster and just keeps the same ratio of pressure in the front and rear lines.

It also has a sensor that detects if the pressure in one circuit is lower than the other, if that happens the dash brake light comes on .