Air in brake lines

[Blue73SuperBeetle]

I have air in the brake lines of my '73 Super Beetle that I can't seem to get out by simply bleeding the lines. Anybody else have this problem, and what can I do to get rid of the air in the lines?

[keifernet]

spell it out, what have you changed/checked, procedure your following etc.

could be a few things, 1: actually air, due to bad component leak or other, or 2: just shoe adjustment making it seem like air....

[Blue73SuperBeetle]

I don't think it's shoe adjustment, I double checked that, and all shoes are adjusted so they are backed off just a bit from rubbing when the wheel is turned.

It could be a component leak, because right after I bleed the lines it seems to be better, then gradually deteriorates. How does one find a component leak? All fittings are tight, I double checked that. When I press the pedal it feels like one or more shoes makes contact very soon, then I have to make one more pump and the other(s) then make contact soon.

It has done this since I replaced a bad master cylinder.

[keifernet]

Okay, well, are you having to add any fluid? A very common thing is the front to rear metal line rusts a very small hole in it. look for wetness under the front carpet/mats by the pedal assembly.

or even "new" masters can be iffy, bypass themselves internally, or leak out the rear of the cylinder, look for fluid there too.

Or you could still have a small amount of air, have you re bled the entire system?. since you have just done it and I presume driven it some, you could just get under it and "gravity" bleed it. no pumping just open the bleeders one at a time and look for any tiny air bubbles, close them up when you see only fluid.

also I adjust the shoes up until you cannot turn the wheel at all, then back them off until it does turn, and a little scraping will not hurt , this way you know the shoes are as close to the drum as possible.

[Blue73SuperBeetle]

It is not leaking fluid, I don't have to add any fluid to the reservoir. The brake lines are in good shape, a couple years ago I had to replace a couple rusted lines that were leaking (from the master cylinder to the rear tee, and the right rear line from the tee). I've bled the entire system. Is there any way to tell if there's air in the master cylinder?

I just read on vwhelp.com that the proper way to adjust VW brakes is to adjust them until they start to rub, press the brake pedal to center the shoes, then readjust them. I haven't tried this.

Thanks for the help. If I can't get it working properly I'll just put disc brakes on the front. I had front drums on a '77 CJ-7 I used to have, and I never had any trouble with them.

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Check to make sure the brake reservoir cap is venting properly. I have a 1972 super and the tiny holes that are supposed to be under the clip on cover on the cap were not fully punched through. When I bled the brakes, a vacuum was created in the reservoir and it was actually pulling air into the wheel cylindars as I opened the bleeder valves. Just pry off the cover on the cap and poke a pin or a nail through the tiny vent holes to ensure they aren't clogged or something.

[Blue73SuperBeetle]

Thanks for the tip, makes sense. I'll try that.