Bleeding Brakes

[andya_andya]

I'm not happy with the performance of the brakes. I can push the pedal to the floor while in fourth gear and not lock up the wheels.

Before I start adjusting the shoes I tried bleeding the brake system and I had a problem with front right.

A very tiny amount of turn on the bleeder and it goes from being fully closed to being open with continual air being sucked in as I press the brake pedal (I'm using a hose from the bleeder into a bottle with the end submerged in brake fluid, bottle is higher than bleeder).

If I try to turn the bleeder the smallest amount I can to try to close it a bit more it is then fully closed and I can't bleed it.

I presumed the air is being sucked in via the threads. There are no fluid leaks in the lines. I put anti-seize grease on the threads and that didn't help.

During bleeding all four corners I did get to a point where the brake pedal felt stiffer but that went away during the process. I am not sure the pattern. This is my first time bleeding brakes.

CNC pedals with CNC reservoir.

Thanks, Andy

[joemama]

You might already be doing this, but since you said this is your first time. First, adjust all the brakes so they are tight against the drums. Have a helper pump the pedal to build up pressure, he/she will continue to keep pressure on the pedal You now open the bleed screw, and close it before the helper has the pedal all the way down, this way air cant get back in. Make sure your reservoir always has fluid in it, otherwise you are pumping air in. Once no more air comes out, go back and re adjust your brakes.

[Daddy o's 67]

If you have 2 master cyls, you have to bleed both front and rear on one side at the same time.

Pump up brakes, hold, open right front, close, open right rear, close. Then repeat same process for left side.

[MrGoodtunes]

[andya_andya]

Thanks for the replies! Bottle is higher because I read somewhere that was the right way but I don't know.

I've managed to get the air bubbles to stop on that one bleeder but I think I will replace it.

Still bad brakes though. Tried adjusting the stars on the back but I didn't feel any clicks and it didn't help. I am going to jack it up, remove all four wheels make the adjustment that way.

Andy

[Wulfthang]

I used to use a pressure bleeder but gave that up after a hose came off! Now I use a vacuum bleeder, the kind that uses air pressure to cause the suction at the hose. I use an old spray paint gun tank as the holding tank for the fluid. It keeps it clean for re-use.

Simple, convenient, no helper required, no mess and it works. All you have to do, is make sure to keep the reservoir filled or it'll suck air into the system. Slip the hose onto the bleeder screw, trigger the vacuum button and open the bleeder. Watch the fluid flow by. I usually wedge the air pressure button under a tire so I can go fill the reservoir. Doing that, also allows me to pump the pedals and the turning brake handle.

A tips about bleeder screws.
They seal on the end, the cone end screwing down into a hole, not the threads. The threads leak a lot of times. If you're using a pressure bleeder or somebodies foot, leaky threads will just make a mess. However:! Leaky threads with a vacuum bleeder, looks like air in the line!

It only took a quart of brake fluid cycled thru to figure it out! The answer is to remove the bleed screws, clean the threads, wrap them in Teflon tape being careful to not get any on the cone end and reassemble. The Teflon tape seals the loose threads so no air gets sucked in to fool you! I get two or three "bleedings" out of them before the tape needs to be replaced.

[andya_andya]

Here is what I am observing.

Rail is in neutral, back is jacked up so wheels are off the ground.
Brake pedal not depressed, both wheels rotate.
Use a strap to press and hold the brake pedal half way
Turn the stars, observe the pads and keep turning the wheel until the pad friction stops it from turning

So far so good.

Then I removed the strap and released the brake pedal and the wheels don't turn.

So it seems pressing the brake pedal has no effect at the rear.

However I was able to pump the brake pedal and bleed both rears successfully.

Update - the cutting brakes work! So the problem is somehow in between?

What could be happening?

I have this "hand brake" box in between the brake pedal and the cutting brakes. I can't seem to depress it. I also have a pressure switch for the brake lights that doesn't seem to turn the lights on.

Thanks, Andy

[Wulfthang]

When you say "turn the stars", are you referring to the brake star adjusters on drum brakes? If so, it sounds almost as if you're trying to preload the brakes!? You adjust the star wheels to take up the appropriate slack with no brakes applied and they're never tightened up tight enough to lock up the wheel.

I'm not familiar with VW drum brakes but in all of the ones that I worked on, the Star Wheel was part of the self adjuster mechanism. It just also happened to be a good way to adjust it by hand even though it was never made for that. I always tightened it up enough so I just barely heard the shoes scrape..didn't I?... Maybe not.... Oh yeah..There it is...no, it's gone again. In other words, better a little to loose rather than a little to tight.

After all, it is a "Self Adjuster". Get it close on the loose side and let the adjuster do it's job. A few brisk back up's and quick slam stops and it's perfect. All of this is assuming that they're self adjusting drum brakes.!?

[andya_andya]

[Wulfthang]

Making brakes work right can sometimes cause temporary insanity! First, do not adjust anything with the brake pedal depressed.
You have to start at the beginning. Set the clearance in the brake pedal pushrod first. Then set the shoe clearance with the star adjusters. Lastly, bleed the brakes. If that doesn't work, find the problem and fix it.

Yes, the parking brake lock can fail. I had one that a friend tried to release by just pulling up on it. It pulled the oring off the end inside. You have to mash the brake pedal first.

[joemama]

I dont know where you are, but most places require an independent/separate (basically mechanical) emergency brake set up to be street legal. I like a separate mechanical brake, particularly the vw pull up handle, because it comes in very handy in all sorts of offroad situations.

[Wulfthang]

They didn't require an emergency brake when I took my rail thru the "Level Three Inspection" at DMV to get it street legal.

I do have a "parking brake" though! It's a piece of rope! It's hooked to a top frame rail. Then I pull up the steering brake handle and tie it in place. It locks one rear wheel.

Andy. Check your messages. I sent you a PM.

[andya_andya]

This is what is required for street legal in Arizona:

https://azstateparks.com/ohv-laws-regulations

I find it strange that the cutting brakes work but the master cylinder does not. Seems the brake shoes are adjusted OK and no air from cutting brakes to rear drums?

I did notice when actuating the brake pedal that some brake fluid shoots up from a hole at the bottom. Some websites say this is normal as the piston cylinder moves past the reservoir opening and some say it is not normal. So much conflicting advice about brake systems out there.

I found the instructions for the CNC cutting brake here:

https://www.appletreeauto.com/files/pdfs/cnc452.pdf

and it includes bleeding so I will give that a try later today.

Andy

[dustymojave]

You kinda went right past the adjustment issue.

You should jack up the corner or end of the car for the brakes you're adjusting. Put it on jack stands. Don't be a fool under a car that the jack slipped or the car rolled or...

Turn one star at a time. Lots of other cars with more modern self adjusting drum brakes only have 1 star. But air cooled VWs have 2 adjuster stars per wheel. Turn that star until the wheel won't turn anymore. Stop turning the star. You don't have to torque it down. Just stop the wheel. Then back it off until the wheel will turn and you barely hear and feel the shoe rubbing. It will only rub part of the way around. The drums do NOT stay perfectly round. But that's OK. Then you turn it so you can adjust the other star on that wheel. Do the same. Note that you have to flick the star tips the other direction from the 1st star. Again, turn the star until the wheel stops turning. Then back it off until you feel and hear the drum rubbing on the shoes. It should have a little more resistance now than after the 1st star.

Then go to the next wheel. You need to adjust BOTH stars on ALL 4 wheels.

Then think about bleeding. I suspect you may have some issue with your Park-Loc or maybe with your steering brakes. But don't jump straight to that. Get the brakes ALL adjusted 1st.

The suggestion above to snug the brake shoes against the drum can help with bleeding. Do that with the 2nd star on each wheel. You can't tighten the other star once 1 is tight. But don't forget to properly back them off after bleeding.

I have replaced brake shoes on SO MANY VWs that one end of each shoe was worn to metal while the other end was untouched like new because nobody EVER adjusted the brakes, including whoever had replaced the shoes before. The brake shoes should be adjusted at least every other oil change. The hand brake, if it has one should ALSO be adjusted periodically to ensure it doesn't go too high when pulled.
_________________
Richard
Offroading VW based cars since 1965
Tech Inspection 1963 - 2012 SCCA/SCORE/HDRA/MORE/MDR +
Retired from building Bajas, Fiberglass Buggies and Rails in the Mojave Desert. Also Sprints & Midgets, Dry Lakes, Road Race cars. All types New and Vintage
SoCalBajas Member
Kicked Cancer's A$$...1st and 2nd round...Fight ain't over yet.

[Wulfthang]

Thanks Dustymojave for clarifying that VW star wheels aren't part of an automatic adjuster system. I've worked on lots of cars and motorcycles but I'm not familiar with VW drum brakes. My Rail is all discs.

Yeah, I had a hydraulic parking lock malfunction one time. Could be. What about the adjuster between the M/C and the pedal?

What about the front brakes? Does it have any and do they work?

[andya_andya]

Thanks for the great replies!

I put teflon on both rear bleeders and re-bleeded according to those CNC instructions. No air coming out.

Brakes are working better now.

I have front drums and no proportioning valve so I can get the fronts to lock and the rears don't.

I haven't taken the drums apart yet to see the condition of the entire shoes but I can see one shoe is down to 1/16" so needs to be replaced. May as well do all of them at the same time.

Andy

[dustymojave]

Definitely good to replace shoes that worn.

Also keep in mind that VW based buggies and Bajas usually have larger rear tires than fronts and a great portion of the weight on the rear wheels, plus if they are used on dirt, there are different needs there than on pavement too. All of the above conspire to change the brake bias need from accent on the front to accent on the rear.

A larger heavier tire and wheel have much more rotational inertia than smaller ones. AND, the larger diameter provides more leverage from the tread to rotate the tire.

On dirt, if your front brakes lock up, you lose steering entirely. If the rears lock up 1st, they simply drag you to a stop while you still have steering.

If you use the right year model and shoe width, you can put front wheel cylinders on the rear and rear cylinders on the front. The different diameter of piston will then give you better braking on the rear while letting up on the front. Same bias change as using a proportioning valve. The wheel cylinder MUST be for the same width shoes. You can't change shoe width without changing backing plates.
_________________
Richard
Offroading VW based cars since 1965
Tech Inspection 1963 - 2012 SCCA/SCORE/HDRA/MORE/MDR +
Retired from building Bajas, Fiberglass Buggies and Rails in the Mojave Desert. Also Sprints & Midgets, Dry Lakes, Road Race cars. All types New and Vintage
SoCalBajas Member
Kicked Cancer's A$$...1st and 2nd round...Fight ain't over yet.

[andya_andya]

Thanks Richard, learning a lot here! Andy